Ettore Majorana centennial and neutrino legacy
NASA Astrophysics Data System (ADS)
Esposito, Salvatore
2007-06-01
"In the world there are various categories of scientists: people of secondary or tertiary standing, who do their best but do not go very far. There are also those of high standing, who come to discoveries of great importance. But then there are geniuses like Galileo and Newton. Well, Ettore was one of them. Majorana had what no one else in the world has...". In this talk we try to put some light on this quite unusual statement by Enrico Fermi about Ettore Majorana, by exploring mainly personal notes left unpublished by the great sicilian physicist. Some emphasis is given on recent achievements about Majorana as a research scientist as well as a teacher in Theoretical Physics.
The Disappearance and Death of Ettore Majorana
NASA Astrophysics Data System (ADS)
Guerra, Francesco; Robotti, Nadia
2013-06-01
At the end of March 1938, Ettore Majorana disappeared under still mysterious circumstances while he was Professor of Theoretical Physics at the University of Naples. We exploit new archival documents that provide evidence that without any doubt he was deceased before September 1939. These include documents pertaining to the foundation of a Fellowship in his name, announced on November 3, 1939, in the journal, The Missions of the Society of Jesus, and documents pertaining to the Police and Vatican inquires after his disappearance. We conclude by discussing the biographical sketch of Majorana that his uncle Giuseppe Majorana wrote before his death in 1940.
Ettore Majorana and the birth of autoionization
NASA Astrophysics Data System (ADS)
Arimondo, Ennio; Clark, Charles W.; Martin, William C.
2010-02-01
In some of the first applications of modern quantum mechanics to the spectroscopy of many-electron atoms, Ettore Majorana in 1931 solved several outstanding problems by developing the theory of autoionization [1]. Later literature makes only sporadic references to this accomplishment. After reviewing his work in its contemporary context, we describe subsequent developments in understanding the spectra treated by Majorana, and extensions of his theory to other areas of physics. We find several puzzles concerning the treatment of Majorana's work in the subsequent literature and the way in which the modern theory of autoionization was developed. [1] The relevant papers are those numbered 3 and 5 in the convenient collection, Ettore Majorana Scientific Papers: On the occasion of the centenary of his birth, ed. G. F. Bassani et al. (SIF, Bologna 2006), where they are accompanied by English translations and commentary. The originals are, respectively, ``I presunti termini anomali dell'elio," E. Majorana, Il Nuovo Cimento 8, 78 (1931) and ``Teoria dei tripletti P' incompleti," E. Majorana, Il Nuovo Cimento 8, 107 (1931). )
A peculiar lecture by Ettore Majorana
NASA Astrophysics Data System (ADS)
Esposito, S.
2006-09-01
We give, for the first time, the English translation of a manuscript by Ettore Majorana, which probably corresponds to the text for a seminar lecture delivered at the University of Naples in 1938, where he lectured on theoretical physics. Some passages reveal a physical interpretation of quantum mechanics which anticipates for several years the Feynman approach in terms of path integrals, independent of the underlying mathematical formulation.
The Physics of Ettore Majorana
NASA Astrophysics Data System (ADS)
Esposito, Salvatore
2014-12-01
Part I. Introducing the Character: 1. Life and myth; 2. The visible side; Part II. Atomic Physics: 3. Two-electron problem; 4. Thomas-Fermi model; Part III. Nuclear and Statistical Physics: 5. Quasi-stationary nuclear states; 6. Theory of ferromagnetism; Part IV. Relativistic Fields and Group Theory; 7. Groups and their applications to quantum mechanics; 8. Dirac equations and some alternatives; Part V. Quantum Field Theory: 9. Scalar electrodynamics; 10. Photons and electrons; Part VI. Fundamental Theories and Other Topics: 11. A 'path integral' approach to quantum mechanics; 12. Fundamental lengths and times; 13. Some more; Part VII. Beyond Majorana: 14. Majorana and condensed matter physics; 15. Majorana neutrinos and other Majorana particles; Appendix; References; Index.
Ettore Majorana: The scientist and the man
NASA Astrophysics Data System (ADS)
Recami, Erasmo
2014-12-01
Ettore Majorana was the brightest Italian theoretical physicist of the XX century (actually, Enrico Fermi regarded him as the brightest in the world of his time, and compared him to Galileo and Newton), even if to some people Majorana is often known mainly for his mysterious disappearance, in 1938, when he was 31. In this paper, we present a panoramic view of the main scientific articles published by him, as well as their significance. We also briefly outline his life, the biographical data being based on letters, documents, testimonies discovered or collected by the author during more than four decades, and contained since 1986 in Recami's book quoted in the text. Finally, extensive information and comments are added with regard to the scientific manuscripts left unpublished by Majorana. Two pictures complete the paper.
Ettore Majorana's Course on Theoretical Physics: A Recent Discovery
NASA Astrophysics Data System (ADS)
Drago, Antonino; Esposito, Salvatore
2007-09-01
We analyze in some detail the course of Theoretical Physics held by Ettore Majorana at the University of Naples in 1938, just before his mysterious disappearance. In particular we present the recently discovered "Moreno Paper", where all the lecture notes are reported. Six of these lectures are not present in the collection of the original manuscripts conserved at the Domus Galilaeana in Pisa, consisting of only ten lectures.
The disappearance of Ettore Majorana: an analytic examination
NASA Astrophysics Data System (ADS)
Esposito, S.
2010-05-01
The many recent researches into the mysterious disappearance of Ettore Majorana, one of the greatest minds of theoretical physics in the twentieth century, are summarised and discussed in some detail. The fate of the Italian scientist is argued to be intimately related to the final months of his life in Naples, from where he decided to disappear in March 1938. This analysis of accurate and detailed investigations performed in the last few years, together with facts already known, reveals a fascinating and intriguing picture, which was previously unexpected. New light on the disappearance of Majorana, a mystery that has lasted for more than 70 years, then emerges.
Teaching theoretical physics: The cases of Enrico Fermi and Ettore Majorana
NASA Astrophysics Data System (ADS)
De Gregorio, Alberto; Esposito, Salvatore
2007-09-01
We report on theoretical courses by Enrico Fermi and Ettore Majorana, which give evidence of the first appearance and further development of quantum mechanics teaching in Italy. On the basis of original documents, we compare Fermi and Majorana's approaches. A detailed analysis is made of Fermi's course on theoretical physics attended by Majorana in 1927-28. Three (previously unknown) programs on advanced physics courses submitted by Majorana to the University of Rome between 1933 and 1936 and the course he taught in Naples in 1938 complete our analysis. Fermi's phenomenological approach resounded in Majorana, who combined it with a deeper theoretical approach, closer to the contemporary way of presenting quantum mechanics.
NASA Astrophysics Data System (ADS)
Recami, Erasmo
2010-04-01
I was delighted to read Salvatore Esposito's review (March pp44-45) of A Brilliant Darkness, João Magueijo's book about the Italian physicist Ettore Majorana. As no less a figure than Enrico Fermi regarded Majorana as the brightest theoretical physicist of his time, I was happy to see that Majorana's name is at last becoming famous outside Italy. The fact is that although most commentaries about Majorana's work appear in English, over the past 50 years nearly everyone who has written about Majorana's life has done so in Italian.
Majorana: From Atomic and Molecular, to Nuclear Physics
NASA Astrophysics Data System (ADS)
Pucci, R.; Angilella, G. G. N.
2006-10-01
In the centennial of Ettore Majorana's birth (1906-1938?), we re-examine some aspects of his fundamental scientific production in atomic and molecular physics, including a not well known short communication. There, Majorana critically discusses Fermi's solution of the celebrated Thomas-Fermi equation for electron screening in atoms and positive ions. We argue that some of Majorana's seminal contributions in molecular physics already prelude to the idea of exchange interactions (or Heisenberg-Majorana forces) in his later workson theoretical nuclear physics. In all his papers, he tended to emphasize the symmetries at the basis of a physical problem, as well as the limitations, rather than the advantages, of the approximations of the method employed.
NASA Astrophysics Data System (ADS)
Liu, Xin; Li, Xiaopeng; Deng, Dong-Ling; Liu, Xiong-Jun; Das Sarma, S.
2016-07-01
We propose a systematic magnetic-flux-free approach to detect, manipulate, and braid Majorana fermions in a semiconductor-nanowire-based topological Josephson junction by utilizing the Majorana spin degree of freedom. We find an intrinsic π -phase difference between spin-triplet pairings enforced by the Majorana zero modes (MZMs) at the two ends of a one-dimensional spinful topological superconductor. This π phase is identified to be a spin-dependent superconducting phase, referred to as the spin phase, which we show to be tunable by controlling spin-orbit coupling strength via electric gates. This electric controllable spin phase not only affects the coupling energy between MZMs but also leads to a fractional Josephson effect in the absence of any applied magnetic flux, which enables the efficient topological qubit readout. We thus propose an all-electrically controlled superconductor-semiconductor hybrid circuit to manipulate MZMs and to detect their non-Abelian braiding statistics properties. Our work on spin properties of topological Josephson effects potentially opens up a new thrust for spintronic applications with Majorana-based semiconductor quantum circuits.
Aalseth, Craig E.; Aguayo Navarrete, Estanislao; Amman, M.; Avignone, F. T.; Back, Henning O.; Bai, Xinhua; Barabash, Alexander S.; Barbeau, P. S.; Bergevin, M.; Bertrand, F.; Boswell, M.; Brudanin, V.; Bugg, William; Burritt, Tom H.; Busch, Matthew; Capps, Greg L.; Chan, Yuen-Dat; Collar, J. I.; Cooper, R. J.; Creswick, R.; Detwiler, Jason A.; Diaz, J.; Doe, Peter J.; Efremenko, Yuri; Egorov, Viatcheslav; Ejiri, H.; Elliott, S. R.; Ely, James H.; Esterline, James H.; Farach, H. A.; Fast, James E.; Fields, N.; Finnerty, P.; Fraenkle, Florian; Gehman, Victor M.; Giovanetti, G. K.; Green, M.; Guiseppe, Vincente; Gusey, K.; Hallin, A. L.; Harper, Gregory; Hazama, R.; Henning, Reyco; Hime, Andrew; Hong, H.; Hoppe, Eric W.; Hossbach, Todd W.; Howard, Stanley; Howe, M. A.; Johnson, R. A.; Keeter, K.; Keillor, Martin E.; Keller, C.; Kephart, Jeremy D.; Kidd, M. F.; Knecht, A.; Kochetov, Oleg; Konovalov, S.; Kouzes, Richard T.; LaRoque, B. H.; Leviner, L.; Loach, J. C.; Luke, P.; MacMullin, S.; Marino, Michael G.; Martin, R. D.; Medlin, D.; Mei, Dong-Ming; Miley, Harry S.; Miller, M. L.; Mizouni, Leila; Myers, Allan W.; Nomachi, Masaharu; Orrell, John L.; Peterson, David; Phillips, D.; Poon, Alan; Perevozchikov, O.; Perumpilly, Gopakumar; Prior, Gersende; Radford, D. C.; Reid, Douglas J.; Rielage, Keith; Robertson, R. G. H.; Rodriguez, Larry; Ronquest, M. C.; Salazar, Harold; Schubert, Alexis G.; Shima, T.; Shirchenko, M.; Sobolev, V.; Steele, David; Strain, J.; Swift, Gary; Thomas, K.; Timkin, V.; Tornow, W.; Van Wechel, T. D.; Vanyushin, I.; Varner, R. L.; Vetter, Kai; Vorren, Kris R.; Wilkerson, J. F.; Wolfe, B. A.; Xiang, W.; Yakushev, E.; Yaver, Harold; Young, A.; Yu, Chang-Hong; Yumatov, V.; Zhang, C.
2011-08-01
The Majorana Collaboration is assembling an array of HPGe detectors to search for neutrinoless double-beta decay in 76Ge. Initially, Majorana aims to construct a prototype module to demonstrate the potential of a future 1-tonne experiment. The design and potential reach of this prototype Demonstrator module are presented.
Chesi, Stefano; Jaffe, Arthur; Loss, Daniel; Pedrocchi, Fabio L.
2013-11-15
We investigate the role that vortex loops play in characterizing eigenstates of interacting Majoranas. We give some general results and then focus on ladder Hamiltonian examples as a test of further ideas. Two methods yield exact results: (i) A mapping of certain spin Hamiltonians to quartic interactions of Majoranas shows that the spectra of these two examples coincide. (ii) In cases with reflection-symmetric Hamiltonians, we use reflection positivity for Majoranas to characterize vortices in the ground states. Two additional methods suggest wider applicability of these results: (iii) Numerical evidence suggests similar behavior for certain systems without reflection symmetry. (iv) A perturbative analysis also suggests similar behavior without the assumption of reflection symmetry.
Lee, Jaehoon; Wilczek, Frank
2013-11-27
Motivated by the problem of identifying Majorana mode operators at junctions, we analyze a basic algebraic structure leading to a doubled spectrum. For general (nonlinear) interactions the emergent mode creation operator is highly nonlinear in the original effective mode operators, and therefore also in the underlying electron creation and destruction operators. This phenomenon could open up new possibilities for controlled dynamical manipulation of the modes. We briefly compare and contrast related issues in the Pfaffian quantum Hall state.
Simulating the exchange of Majorana zero modes with a photonic system
NASA Astrophysics Data System (ADS)
Xu, Jin-Shi; Sun, Kai; Han, Yong-Jian; Li, Chuan-Feng; Pachos, Jiannis K.; Guo, Guang-Can
2016-10-01
The realization of Majorana zero modes is in the centre of intense theoretical and experimental investigations. Unfortunately, their exchange that can reveal their exotic statistics needs manipulations that are still beyond our experimental capabilities. Here we take an alternative approach. Through the Jordan-Wigner transformation, the Kitaev's chain supporting two Majorana zero modes is mapped to the spin-1/2 chain. We experimentally simulated the spin system and its evolution with a photonic quantum simulator. This allows us to probe the geometric phase, which corresponds to the exchange of two Majorana zero modes positioned at the ends of a three-site chain. Finally, we demonstrate the immunity of quantum information encoded in the Majorana zero modes against local errors through the simulator. Our photonic simulator opens the way for the efficient realization and manipulation of Majorana zero modes in complex architectures.
Simulating the exchange of Majorana zero modes with a photonic system
Xu, Jin-Shi; Sun, Kai; Han, Yong-Jian; Li, Chuan-Feng; Pachos, Jiannis K.; Guo, Guang-Can
2016-01-01
The realization of Majorana zero modes is in the centre of intense theoretical and experimental investigations. Unfortunately, their exchange that can reveal their exotic statistics needs manipulations that are still beyond our experimental capabilities. Here we take an alternative approach. Through the Jordan–Wigner transformation, the Kitaev's chain supporting two Majorana zero modes is mapped to the spin-1/2 chain. We experimentally simulated the spin system and its evolution with a photonic quantum simulator. This allows us to probe the geometric phase, which corresponds to the exchange of two Majorana zero modes positioned at the ends of a three-site chain. Finally, we demonstrate the immunity of quantum information encoded in the Majorana zero modes against local errors through the simulator. Our photonic simulator opens the way for the efficient realization and manipulation of Majorana zero modes in complex architectures. PMID:27779181
Orrell, John; Hoppe, Eric
2013-11-20
Working as part of a collaborative team, PNNL is bringing its signature capability in ultra-low-level detection to help search for a rare form of radioactive decay-never before detected-called "neutrinoless double beta decay" in germanium. If observed, it would demonstrate neutrinos are Majorana-type particles. This discovery would show neutrinos are unique among fundamental particles, having a property whereby the matter and anti-matter version of this particle are indistinguishable. Physicist John L. Orrell explains how they rely on the Shallow Underground Laboratory to conduct the research.
Orrell, John; Hoppe, Eric
2016-07-12
Working as part of a collaborative team, PNNL is bringing its signature capability in ultra-low-level detection to help search for a rare form of radioactive decay-never before detected-called "neutrinoless double beta decay" in germanium. If observed, it would demonstrate neutrinos are Majorana-type particles. This discovery would show neutrinos are unique among fundamental particles, having a property whereby the matter and anti-matter version of this particle are indistinguishable. Physicist John L. Orrell explains how they rely on the Shallow Underground Laboratory to conduct the research.
Elliott, Steven Ray; Elliott, Steve; Gehman, V M; Guiseppe, V E; Hime, A; Rielage, K; Rodriguez, L; Wouters, J M; Aalseth, C E; Akashi - Ronquest, M; Amman, M; Amsbaugh, J F; Avignone Ill, F T; Back, H O; Baktash, C; Barabash, A S; Barbeau, P; Beene, J R; Bergevin, M; Bertrand, F E; Boswell, M; Brudanin, V; Bugg, W; Burritt, T H; Chan, Y - D; Cianciolo, T V; Collar, J; Creswick, R; Cromaz, M; Detwiler, J A; Doe, P J; Dunmore, J A; Efremenko, Yu; Egorov, V; Ejiri, H; Ely, J; Esterline, J; Farach, H; Farmer, T; Fast, J; Finnerty, P; Fujikawa, B; Greenberg, C; Gusey, K; Hallin, A L; Hazama, R; Henning, R; Hossbach, T; Hoppe, E; Howe, M A; Hurley, D; Hyronimus, B; Johnson, R A; Keillor, M; Keller, C; Kephart, J; Kidd, M; Kochetov, O; Konovalov, S I; Kouzes, R T; Lesko, K T; Leviner, L; Luke, P; Macmullin, S; Marino, M G; Mcdonald, A B; Mei, D - M; Miley, H S; Myers, A W; Nomachi, M; Odom, B; Orrell, J; Poon, A W P; Prior, G; Radford, D C; Reeves, J H; Riley, N; Robertson, R G H; Rykaczewski, K P; Schubert, A G; Shima, T; Shirchenko, M; Timkin, V; Thompson, R; Tornow, W; Tull, C; Van Wechel, T D; Vanyushin, I; Varner, R L; Vetter, K; Warner, R; Wilkerson, J F; Yakushev, E; Young, A R; Yu, C - H; Yumatov, V; Yin, Z - B
2008-01-01
Building a 0{nu}{beta}{beta} experiment with the ability to probe neutrino mass in the inverted hierarchy region requires the combination of a large detector mass sensitive to 0{nu}{beta}{beta}, on the order of 1 ton, and unprecedented background levels, on the order of or less than 1 count per year in the 0{nu}{beta}{beta} signal region. The MAJORANA Collaboration proposes a design based on using high-purity enriched {sup 76}Ge crystals deployed in ultra-low background electroformed Cu cryostats and using modern analysis techniques that should be capable of reaching the required sensitivity while also being scalable to a 1-ton size. To demonstrate feasibility, the collaboration plans to construct a prototype system, the MAJORANA Demonstrator, consisting of 30 kg of 86% enriched {sup 76}Ge detectors and 30 kg of natural or isotope-76-depleted Ge detectors. We plan to deploy and evaluate two different Ge detector technologies, one based on a p-type configuration and the other on n-type.
Status of the MAJORANA DEMONSTRATOR
NASA Astrophysics Data System (ADS)
Vasilyev, S.; Abgrall, N.; Arnquist, I. J.; Avignone, F. T.; Balderrot-Barrera, C. X.; Barabash, A. S.; Bertrand, F. E.; Bradley, A. W.; Brudanin, V.; Busch, M.; Buuck, M.; Byram, D.; Caldwell, A. S.; Chan, Y.-D.; Christofferson, C. D.; Cuesta, C.; Detwiler, J. A.; Efremenko, Yu.; Ejiri, H.; Elliott, S. R.; Galindo-Uribarri, A.; Gilliss, T.; Giovanetti, G. K.; Goett, J.; Green, M. P.; Gruszko, J.; Guinn, I.; Guiseppe, V. E.; Henning, R.; Hoppe, E. W.; Howard, S.; Howe, M. A.; Jasinski, B. R.; Keeter, K. E.; Kidd, M. F.; Konovalov, S. I.; Kouzes, R. T.; LaFerriere, B. D.; Leon, J.; MacMullin, J.; Martin, R. D.; Meijer, S. J.; Mertens, S.; Orrell, J. L.; O'Shaughnessy, C.; Poon, A. W. P.; Radford, D. C.; Rager, J.; Rielage, K.; Robertson, R. G. H.; Romero-Romero, E.; Shanks, B.; Shirchenko, M.; Snyder, N.; Suriano, A. M.; Tedeschi, D.; Trimble, J. E.; Varner, R. L.; Vetter, K.; Vorren, K.; White, B. R.; Wilkerson, J. F.; Wiseman, C.; Xu, W.; Yakushev, E.; Yu, C.-H.; Yumatov, V.; Zhitnikov, I.
2017-01-01
The MAJORANA Collaboration is constructing the MAJORANA DEMONSTRATOR, an ultralow background, 40-kg modular high purity Ge (HPGe) detector array to search for neutrinoless double-beta decay (0νββ-decay) in 76Ge. The goal of the experiment is to demonstrate a background rate at or below 3 counts/(t-y) in the 4 keV region of interest (ROI) around the 2039 keV Q-value for 76Ge 0νββ-decay. In this paper, the status of the MAJORANA DEMONSTRATOR, including its design and measurements of properties of the HPGe crystals is presented.
Majorana Braiding with Thermal Noise
NASA Astrophysics Data System (ADS)
Pedrocchi, Fabio L.; DiVincenzo, David P.
2015-09-01
We investigate the self-correcting properties of a network of Majorana wires, in the form of a trijunction, in contact with a parity-preserving thermal environment. As opposed to the case where Majorana bound states are immobile, braiding Majorana bound states within a trijunction introduces dangerous error processes that we identify. Such errors prevent the lifetime of the memory from increasing with the size of the system. We confirm our predictions with Monte Carlo simulations. Our findings put a restriction on the degree of self-correction of this specific quantum computing architecture.
Detecting Majorana nonlocality using strongly coupled Majorana bound states
NASA Astrophysics Data System (ADS)
Rubbert, S.; Akhmerov, A. R.
2016-09-01
Majorana bound states (MBS) differ from the regular zero energy Andreev bound states in their nonlocal properties, since two MBS form a single fermion. We design strategies for detection of this nonlocality by using the phenomenon of Coulomb-mediated Majorana coupling in a setting which still retains falsifiability and does not require locally separated MBS. Focusing on the implementation of MBS based on the quantum spin Hall effect, we also design a way to probe Majoranas without the need to open a magnetic gap in the helical edge states. In the setup that we analyze, long range MBS coupling manifests in the h /e magnetic flux periodicity of tunneling conductance and supercurrent. While h /e is also the periodicity of Aharonov-Bohm effect and persistent current, we show how to ensure its Majorana origin by verifying that switching off the charging energy restores h /2 e periodicity conventional for superconducting systems.
Majorana neutrinos and magnetic fields
NASA Astrophysics Data System (ADS)
Schechter, J.; Valle, J. W. F.
1981-10-01
It is stressed that if neutrinos are massive they are probably of "Majorana" type. This implies that their magnetic-moment form factor vanishes identically so that the previously discussed phenomenon of spin rotation in a magnetic field would not appear to take place. We point out that Majorana neutrinos can, however, have transition moments. This enables an inhomogeneous magnetic field to rotate both spin and "flavor" of a neutrino. In this case the spin rotation changes particle to antiparticle. The spin-flavor-rotation effect is worked out in detail. We also discuss the parametrization and calculation of the electromagnetic form factors of Majorana neutrinos. Our discussion takes into account the somewhat unusual quantum theory of massive Majorana particles.
NASA Astrophysics Data System (ADS)
Plugge, Stephan; Rasmussen, Asbjørn; Egger, Reinhold; Flensberg, Karsten
2017-01-01
Quantum information protected by the topology of the storage medium is expected to exhibit long coherence times. Another feature is topologically protected gates generated through braiding of Majorana bound states (MBSs). However, braiding requires structures with branched topological segments which have inherent difficulties in the semiconductor-superconductor heterostructures now believed to host MBSs. In this paper, we construct quantum bits taking advantage of the topological protection and non-local properties of MBSs in a network of parallel wires, but without relying on braiding for quantum gates. The elementary unit is made from three topological wires, two wires coupled by a trivial superconductor and the third acting as an interference arm. Coulomb blockade of the combined wires spawns a fractionalized spin, non-locally addressable by quantum dots used for single-qubit readout, initialization, and manipulation. We describe how the same tools allow for measurement-based implementation of the Clifford gates, in total making the architecture universal. Proof-of-principle demonstration of topologically protected qubits using existing techniques is therefore within reach.
Status of the MAJORANA DEMONSTRATOR
Cuesta, C; Abgrall, N.; Arnquist, I. J.; Avignone, III, F. T.; Barabash, A.S.; Bertrand, F. E.; Bradley, A. W.; Brudanin, V.; Busch, M.; Byram, D.; Caldwell, Adam S; Chan, Y-D; Christofferson, C. D.; Chu, P.-H.; Detwiler, J. A.; Efremenko, Yu.; Ejiri, H.; Elliott, S. R.; Galindo-Uribarri, A; Gilliss, T.; Green, M. P.; Gruszko, J; Guinn, I S; Guiseppe, V E; Henning, R.; Howard, S.; Howe, M. A.; Keeter, K.J.; Kidd, M. F.; Konovalov, S.I.; Kouzes, R. T.; LaFerriere, B. D.; Leon, J.; MacMullin, J.; Massarczyk, R.; Meijer, S. J.; Orrell, J. L.; O'Shaughnessy, C.; Radford, D. C.; Rager, J.; Robertson, R.G.H.; Romero-Romero, E.; Snyder, N; Suriano, A. M.; Tedeschi, D; Trimble, J. E.; Vasilyev, S.; et al.
2015-01-01
The MAJORANA Collaboration is constructing the MAJORANA DEMONSTRATOR, an ultra-low background, modular, HPGe detector array with a mass of 44-kg (29 kg Ge-76 and 15 kg Ge-nat) to search for neutrinoless double beta decay in Ge-76. The next generation of tonne-scale Ge-based neutrinoless double beta decay searches will probe the neutrino mass scale in the inverted-hierarchy region. The MAJORANA DEMONSTRATOR is envisioned to demonstrate a path forward to achieve a background rate at or below 1 count/tonne/year in the 4 keV region of interest around the Q-value of 2039 keV. The MAJO-RANA DEMONSTRATOR follows a modular implementation to be easily scalable to the next generation experiment. First, the prototype module was assembled; it has been continuously taking data from July 2014 to June 2015. Second, Module 1 with more than half of the total enriched detectors and some natural detectors has been assembled and it is being commissioned. Finally, the assembly of Module 2, which will complete MAJORANA DEMONSTRATOR, is already in progress.
NASA Astrophysics Data System (ADS)
Al-Hashimi, M. H.; Shalaby, A. M.; Wiese, U.-J.
2017-03-01
Motivated by potential applications to ultracold matter, we perform a theoretical study of Majorana fermions confined to a finite volume, whose boundary conditions are characterized by self-adjoint extension parameters. While the boundary conditions for Dirac fermions in (1 +1 )-d are characterized by a 1-parameter family, λ =-λ*, of self-adjoint extensions, for Majorana fermions λ is restricted to ±i . Based on this result, we compute the frequency spectrum of Majorana fermions confined to a 1-d interval. The boundary conditions for Dirac fermions confined to a 3-d region of space are characterized by a 4-parameter family of self-adjoint extensions, which is reduced to two distinct 1-parameter families for Majorana fermions. We also consider the problems related to the quantum mechanical interpretation of the Majorana equation as a single-particle equation. Furthermore, the equation is related to a relativistic Schrödinger equation that does not suffer from these problems. Here we restrict ourselves to theoretical considerations without yet focusing on concrete cold matter applications.
Status of the Majorana Demonstrator
Cuesta, C.; Buuck, M.; Detwiler, J. A.; Gruszko, J.; Guinn, I. S.; Leon, J.; Robertson, R. G. H.; Abgrall, N.; Bradley, A. W.; Chan, Y.-D.; Mertens, S.; Poon, A. W. P.; Arnquist, I. J.; Hoppe, E. W.; Kouzes, R. T.; LaFerriere, B. D.; Orrell, J. L.; Avignone, F. T.; Baldenegro-Barrera, C. X.; Bertrand, F. E.; and others
2015-10-28
The MAJORANA Collaboration is constructing the MAJORANA DEMONSTRATOR, an ultra-low background, modular, HPGe detector array with a mass of 44-kg (29 kg {sup 76}Ge and 15 kg {sup nat}Ge) to search for neutrinoless double beta decay in {sup 76}Ge. The next generation of tonne-scale Ge-based neutrinoless double beta decay searches will probe the neutrino mass scale in the inverted-hierarchy region. The MAJORANA DEMONSTRATOR is envisioned to demonstrate a path forward to achieve a background rate at or below 1 count/tonne/year in the 4 keV region of interest around the Q-value of 2039 keV. The MAJORANA DEMONSTRATOR follows a modular implementation to be easily scalable to the next generation experiment. First, the prototype module was assembled; it has been continuously taking data from July 2014 to June 2015. Second, Module 1 with more than half of the total enriched detectors and some natural detectors has been assembled and it is being commissioned. Finally, the assembly of Module 2, which will complete MAJORANA DEMONSTRATOR, is already in progress.
Majorana Electroformed Copper Mechanical Analysis
Overman, Nicole R.; Overman, Cory T.; Kafentzis, Tyler A.; Edwards, Danny J.; Hoppe, Eric W.
2012-04-30
The MAJORANA DEMONSTRATOR is a large array of ultra-low background high-purity germanium detectors, enriched in 76Ge, designed to search for zero-neutrino double-beta decay. The DEMONSTRATOR will utilize ultra high purity electroformed copper for a variety of detector components and shielding. A preliminary mechanical evaluation was performed on the Majorana prototype electroformed copper material. Several samples were removed from a variety of positions on the mandrel. Tensile testing, optical metallography, scanning electron microscopy, and hardness testing were conducted to evaluate mechanical response. Analyses carried out on the Majorana prototype copper to this point show consistent mechanical response from a variety of test locations. Evaluation shows the copper meets or exceeds the design specifications.
Majorana Zero Modes in Graphene
NASA Astrophysics Data System (ADS)
San-Jose, P.; Lado, J. L.; Aguado, R.; Guinea, F.; Fernández-Rossier, J.
2015-10-01
A clear demonstration of topological superconductivity (TS) and Majorana zero modes remains one of the major pending goals in the field of topological materials. One common strategy to generate TS is through the coupling of an s -wave superconductor to a helical half-metallic system. Numerous proposals for the latter have been put forward in the literature, most of them based on semiconductors or topological insulators with strong spin-orbit coupling. Here, we demonstrate an alternative approach for the creation of TS in graphene-superconductor junctions without the need for spin-orbit coupling. Our prediction stems from the helicity of graphene's zero-Landau-level edge states in the presence of interactions and from the possibility, experimentally demonstrated, of tuning their magnetic properties with in-plane magnetic fields. We show how canted antiferromagnetic ordering in the graphene bulk close to neutrality induces TS along the junction and gives rise to isolated, topologically protected Majorana bound states at either end. We also discuss possible strategies to detect their presence in graphene Josephson junctions through Fraunhofer pattern anomalies and Andreev spectroscopy. The latter, in particular, exhibits strong unambiguous signatures of the presence of the Majorana states in the form of universal zero-bias anomalies. Remarkable progress has recently been reported in the fabrication of the proposed type of junctions, which offers a promising outlook for Majorana physics in graphene systems.
Majorana Thermosyphon Prototype Experimental Setup
Reid, Douglas J.; Guzman, Anthony D.; Munley, John T.
2011-08-01
This report presents the experimental setup of Pacific Northwest National Laboratory’s MAJORANA DEMONSTRATOR thermosyphon prototype cooling system. A nitrogen thermosyphon prototype of such a system has been built and tested at PNNL. This document presents the experimental setup of the prototype that successfully demonstrated the heat transfer performance of the system.
Dynamical generation of Majorana masses
Abada, A.; Le Yaouanc, A.; Oliver, L.; Pene, O.; Raynal, J. )
1990-09-01
We address the general question of the dynamical generation of Majorana masses through quartic interactions of the Nambu--Jona-Lasinio (NJL) type that have both chiral and lepton-number invariances. We make composite the Higgs field of the schemes of spontaneous breaking of the leptonic number; we can thus assign to it a leptonic number {vert bar}{ital L}{vert bar}=2 in a natural way. We consider a Weyl field and write a quartic self-interaction for this field that dynamically breaks chiral and fermion-number invariances and exhibits a whole spectrum of composite particles with different quantum numbers, in addition to a Goldstone Majoron. We compare in detail the Dirac and the Majorana cases. The vacuum degeneracy is the same in both cases, but the vacuum invariances are not. For a single fermion species, we have for the Dirac case a U(1){sub {ital V}{minus}{ital A}}{times}U(1){sub {ital V}+{ital A}} invariance that breaks down to U(1){sub {ital V}} and for the Majorana case a single U(1) invariance that breaks down to the identity {ital open}1. In general the Schwinger-Dyson equation is not the same for both cases, since for Majorana fermions we have propagators of several types. However, in the particular case of a NJL {ital contact} interaction (for Majorana fermions this is {ital the} {ital only} {ital nonvanishing} {ital contact} {ital quartic}/{ital B} {ital interaction}), and with a convenient convention for the coupling, the Schwinger-Dyson equation turns out to have the same form for Dirac and for Majorana fermions. The bound-state boson spectrum is quite different in both cases: for the Dirac case, one has a spectrum {sup 2{ital S}+1}{ital L}{sub {ital J}}({ital S}=0,1) {ital J}{sup {ital P}{ital C}}=0{sup {minus}+},1{sup {minus}{minus}},0{sup ++},1{sup ++},1{sup +{minus}},2{sup ++},. . .
Direct Cavity Detection of Majorana Pairs
NASA Astrophysics Data System (ADS)
Dartiailh, Matthieu C.; Kontos, Takis; Douçot, Benoit; Cottet, Audrey
2017-03-01
No experiment could directly test the particle-antiparticle duality of Majorana fermions, so far. However, this property represents a necessary ingredient towards the realization of topological quantum computing schemes. Here, we show how to complete this task by using microwave techniques. The direct coupling between a pair of overlapping Majorana bound states and the electric field from a microwave cavity is extremely difficult to detect due to the self-adjoint character of Majorana fermions which forbids direct energy exchanges with the cavity. We show theoretically how this problem can be circumvented by using photoassisted tunneling to fermionic reservoirs. The absence of a direct microwave transition inside the Majorana pair in spite of the light-Majorana coupling would represent a smoking gun for the Majorana self-adjoint character.
Roadmap to Majorana surface codes
NASA Astrophysics Data System (ADS)
Plugge, S.; Landau, L. A.; Sela, E.; Altland, A.; Flensberg, K.; Egger, R.
2016-11-01
Surface codes offer a very promising avenue towards fault-tolerant quantum computation. We argue that two-dimensional interacting networks of Majorana bound states in topological superconductor/semiconductor heterostructures hold several key advantages in that direction, concerning both the hardware realization and the actual operation of the code. We here discuss how topologically protected logical qubits in this Majorana surface code architecture can be defined, initialized, manipulated, and read out. All physical ingredients needed to implement these operations are routinely used in topologically trivial quantum devices. By means of quantum interference terms in linear conductance measurements, single-electron pumping protocols, and gate-tunable tunnel barriers, the full set of quantum gates required for universal quantum computation can be achieved. In particular, we show that designated multistep pumping sequences via tunnel-coupled quantum dots realize high-fidelity ancilla states for phase gates.
Status of the Majorana Demonstrator
Cuesta, C.; Abgrall, N.; Arnquist, I. J.; ...
2015-08-06
The Majorana Collaboration is constructing the Majorana Demonstrator, an ultra-low background, 40-kg modular high purity Ge detector array to search for neutrinoless double-beta decay in 76Ge. In view of the next generation of tonne-scale Ge-based neutrinoless double-beta decay searches that will probe the neutrino mass scale in the inverted-hierarchy region, a major goal of the Demonstrator is to demonstrate a path forward to achieving a background rate at or below 1 count/tonne/year in the 4 keV region of interest around the Q-value at 2039 keV. Lastly, the current status of the Demonstrator is discussed, as are plans for its completion.
Status of the Majorana Demonstrator
Cuesta, C.; Abgrall, N.; Arnquist, I. J.; Avignone, III, F. T.; Barabash, A. S.; Bertrand, F. E.; Brudanin, V.; Busch, M.; Buuck, M.; Byram, D.; Caldwell, A. S.; Chan, Y. -D.; Christofferson, C. D.; Detwiler, J. A.; Efremenko, Yu.; Ejiri, H.; Elliott, S. R.; Galindo-Uribarri, A.; Giovanetti, G. K.; Goett, J.; Green, M. P.; Gruszko, J.; Guinn, I. S.; Guiseppe, V. E.; Henning, R.; Hoppe, E. W.; Howard, S.; Howe, M. A.; Jasinski, B. R.; Keeter, K. J.; Kidd, M. F.; Konovalov, S. I.; Kouzes, R. T.; LaFerriere, B. D.; Leon, J.; MacMullin, J.; Martin, R. D.; Meijer, S. J.; Mertens, S.; Orrell, J. L.; O'Shaughnessy, C.; Overman, N. R.; Poon, A. W. P.; Radford, D. C.; Rager, J.; Rielage, K.; Robertson, R. G. H.; Romero-Romero, E.; Schmitt, C.; Shanks, B.; Shirchenko, M.; Snyder, N.; Suriano, A. M.; Tedeschi, D.; Timkin, V.; Trimble, J. E.; Varner, R. L.; Vasilyev, S.; Vetter, K.; Vorren, K.; White, B. R.; Wilkerson, J. F.; Wiseman, C.; Xu, W.; Yakushev, E.; Yu, C. -H.; Yumatov, V.
2015-08-06
The Majorana Collaboration is constructing the Majorana Demonstrator, an ultra-low background, 40-kg modular high purity Ge detector array to search for neutrinoless double-beta decay in ^{76}Ge. In view of the next generation of tonne-scale Ge-based neutrinoless double-beta decay searches that will probe the neutrino mass scale in the inverted-hierarchy region, a major goal of the Demonstrator is to demonstrate a path forward to achieving a background rate at or below 1 count/tonne/year in the 4 keV region of interest around the Q-value at 2039 keV. Lastly, the current status of the Demonstrator is discussed, as are plans for its completion.
The MAJORANA Demonstrator Radioassay Program
Abgrall, N.; Arnquist, Isaac J.; Avignone, F. T.; Back, Henning O.; Barabash, Alexander S.; Bertrand, F.; Boswell, M.; Bradley, A. W.; Brudanin, V.; Busch, Matthew; Buuck, M.; Byram, D.; Caldwell, A. S.; Chan, Yuen-Dat; Christofferson, C. D.; Chu, P. H.; Cuesta, C.; Detwiler, Jason A.; Dunmore, J. A.; Efremenko, Yuri; Ejiri, H.; Elliott, S.; Finnerty, P.; Galindo-Uribarri, A.; Gehman, Victor M.; Gilliss, T.; Giovanetti, G. K.; Goett, J.; Green, M. P.; Gruszko, J.; Guinn, I.; Guiseppe, V. E.; Henning, R.; Hoppe, Eric W.; Howard, S.; Howe, M. A.; Jasinski, B. R.; Johnson, R. A.; Keeter, K.; Kidd, M. F.; Kochetov, Oleg; Konovalov, S.; Kouzes, Richard T.; Laferriere, Brian D.; Leon, Jonathan D.; Loach, J. C.; MacMullin, J.; MacMullin, S.; Martin, R. D.; Massarcyk, R.; Meijer, S. J.; Mertens, S.; Miller, M. L.; Orrell, John L.; O'Shaughnessy, C.; Overman, Nicole R.; Poon, Alan W.; Pushkin, K.; Radford, D. C.; Rager, J.; Rielage, Keith; Robertson, R. G. H.; Romero-Romero, E.; Ronquest, M. C.; Schubert, Alexis G.; Shanks, B.; Shirchenko, M.; Snavely, Kyle J.; Snyder, N.; Steele, David; Suriano, Anne-Marie; Tedeschi, D.; Trimble, J. E.; Varner, R. L.; Vasilyev, Sergey; Vetter, K.; Vorren, Kris R.; White, B. R.; Wilkerson, J. F.; Wiseman, C.; Xu, W.; Yakushev, E.; Yu, Chang-Hong; Yumatov, Vladimir; Zhitnikov, I.
2016-05-03
The Majorana collaboration is constructing the Majorana Demonstrator at the Sanford Underground Research Facility at the Homestake gold mine, in Lead, SD. The apparatus will use Ge detectors, enriched in isotope 76Ge, to demonstrate the feasibility of a large-scale Ge detector experiment to search for neutrinoless double beta decay. The long half-life of this postulated process requires that the apparatus be extremely low in radioactive isotopes whose decays may produce backgrounds to the search. The radioassay program conducted by the collaboration to ensure that the materials comprising the apparatus are suffciently pure is described. The resulting measurements of the radioactiveisotope contamination for a number of materials studied for use in the detector are reported.
The Majorana Parts Tracking Database
Abgrall, N.
2015-01-16
The Majorana Demonstrator is an ultra-low background physics experiment searching for the neutrinoless double beta decay of ^{76}Ge. The Majorana Parts Tracking Database is used to record the history of components used in the construction of the Demonstrator. The tracking implementation takes a novel approach based on the schema-free database technology CouchDB. Transportation, storage, and processes undergone by parts such as machining or cleaning are linked to part records. Tracking parts provides a great logistics benefit and an important quality assurance reference during construction. In addition, the location history of parts provides an estimate of their exposure to cosmic radiation. In summary, a web application for data entry and a radiation exposure calculator have been developed as tools for achieving the extreme radio-purity required for this rare decay search.
The Majorana Parts Tracking Database
Abgrall, N.
2015-01-16
The Majorana Demonstrator is an ultra-low background physics experiment searching for the neutrinoless double beta decay of 76Ge. The Majorana Parts Tracking Database is used to record the history of components used in the construction of the Demonstrator. The tracking implementation takes a novel approach based on the schema-free database technology CouchDB. Transportation, storage, and processes undergone by parts such as machining or cleaning are linked to part records. Tracking parts provides a great logistics benefit and an important quality assurance reference during construction. In addition, the location history of parts provides an estimate of their exposure to cosmic radiation.more » In summary, a web application for data entry and a radiation exposure calculator have been developed as tools for achieving the extreme radio-purity required for this rare decay search.« less
The Majorana Parts Tracking Database
Abgrall, N.; Aguayo, E.; Avignone, F. T.; Barabash, A. S.; Bertrand, F. E.; Brudanin, V.; Busch, M.; Byram, D.; Caldwell, A. S.; Chan, Y-D.; Christofferson, C. D.; Combs, D. C.; Cuesta, C.; Detwiler, J. A.; Doe, P. J.; Efremenko, Yu.; Egorov, V.; Ejiri, H.; Elliott, S. R.; Esterline, J.; Fast, J. E.; Finnerty, P.; Fraenkle, F. M.; Galindo-Uribarri, A.; Giovanetti, G. K.; Goett, J.; Green, M. P.; Gruszko, J.; Guiseppe, V. E.; Gusev, K.; Hallin, A. L.; Hazama, R.; Hegai, A.; Henning, R.; Hoppe, E. W.; Howard, S.; Howe, M. A.; Keeter, K. J.; Kidd, M. F.; Kochetov, O.; Konovalov, S. I.; Kouzes, R. T.; LaFerriere, B. D.; Leon, J. Diaz; Leviner, L. E.; Loach, J. C.; MacMullin, J.; Martin, R. D.; Meijer, S. J.; Mertens, S.; Miller, M. L.; Mizouni, L.; Nomachi, M.; Orrell, J. L.; O׳Shaughnessy, C.; Overman, N. R.; Petersburg, R.; Phillips, D. G.; Poon, A. W. P.; Pushkin, K.; Radford, D. C.; Rager, J.; Rielage, K.; Robertson, R. G. H.; Romero-Romero, E.; Ronquest, M. C.; Shanks, B.; Shima, T.; Shirchenko, M.; Snavely, K. J.; Snyder, N.; Soin, A.; Suriano, A. M.; Tedeschi, D.; Thompson, J.; Timkin, V.; Tornow, W.; Trimble, J. E.; Varner, R. L.; Vasilyev, S.; Vetter, K.; Vorren, K.; White, B. R.; Wilkerson, J. F.; Wiseman, C.; Xu, W.; Yakushev, E.; Young, A. R.; Yu, C. -H.; Yumatov, V.; Zhitnikov, I.
2015-04-01
The MAJORANA DEMONSTRATOR is an ultra-low background physics experiment searching for the neutrinoless double beta decay of 76Ge. The MAJORANA Parts Tracking Database is used to record the history of components used in the construction of the DEMONSTRATOR. Transportation, storage, and processes undergone by parts such as machining or cleaning are linked to part records. Tracking parts provides a great logistics benefit and an important quality assurance reference during construction. In addition, the location history of parts provides an estimate of their exposure to cosmic radiation. A web application for data entry and a radiation exposure calculator have been developed as tools for achieving the extreme radiopurity required for this rare decay search.
The MAJORANA DEMONSTRATOR radioassay program
NASA Astrophysics Data System (ADS)
Abgrall, N.; Arnquist, I. J.; Avignone, F. T.; Back, H. O.; Barabash, A. S.; Bertrand, F. E.; Boswell, M.; Bradley, A. W.; Brudanin, V.; Busch, M.; Buuck, M.; Byram, D.; Caldwell, A. S.; Chan, Y.-D.; Christofferson, C. D.; Chu, P.-H.; Cuesta, C.; Detwiler, J. A.; Dunmore, J. A.; Efremenko, Yu.; Ejiri, H.; Elliott, S. R.; Finnerty, P.; Galindo-Uribarri, A.; Gehman, V. M.; Gilliss, T.; Giovanetti, G. K.; Goett, J.; Green, M. P.; Gruszko, J.; Guinn, I. S.; Guiseppe, V. E.; Henning, R.; Hoppe, E. W.; Howard, S.; Howe, M. A.; Jasinski, B. R.; Johnson, R. A.; Keeter, K. J.; Kidd, M. F.; Kochetov, O.; Konovalov, S. I.; Kouzes, R. T.; LaFerriere, B. D.; Leon, J.; Loach, J. C.; MacMullin, J.; MacMullin, S.; Martin, R. D.; Massarczyk, R.; Meijer, S.; Mertens, S.; Miller, M. L.; Orrell, J. L.; O'Shaughnessy, C.; Overman, N. R.; Poon, A. W. P.; Pushkin, K.; Radford, D. C.; Rager, J.; Rielage, K.; Robertson, R. G. H.; Romero-Romero, E.; Ronquest, M. C.; Schubert, A. G.; Shanks, B.; Shirchenko, M.; Snavely, K. J.; Snyder, N.; Steele, D.; Suriano, A. M.; Tedeschi, D.; Trimble, J. E.; Varner, R. L.; Vasilyev, S.; Vetter, K.; Vorren, K.; White, B. R.; Wilkerson, J. F.; Wiseman, C.; Xu, W.; Yakushev, E.; Yu, C.-H.; Yumatov, V.; Zhitnikov, I.
2016-08-01
The MAJORANA collaboration is constructing the MAJORANA DEMONSTRATOR at the Sanford Underground Research Facility at the Homestake gold mine, in Lead, SD. The apparatus will use Ge detectors, enriched in isotope 76Ge, to demonstrate the feasibility of a large-scale Ge detector experiment to search for neutrinoless double beta decay. The long half-life of this postulated process requires that the apparatus be extremely low in radioactive isotopes whose decays may produce backgrounds to the search. The radioassay program conducted by the collaboration to ensure that the materials comprising the apparatus are sufficiently pure is described. The resulting measurements from gamma-ray counting, neutron activation and mass spectroscopy of the radioactive-isotope contamination for the materials studied for use in the detector are reported. We interpret these numbers in the context of the expected background for the experiment.
The Majorana Demonstrator radioassay program
Abgrall, N.; Arnquist, I. J.; Avignone, F. T.; ...
2016-05-03
The Majorana collaboration is constructing the Majorana Demonstrator at the Sanford Underground Research Facility at the Homestake gold mine, in Lead, SD. The apparatus will use Ge detectors, enriched in isotope 76Ge, to demonstrate the feasibility of a large-scale Ge detector experiment to search for neutrinoless double beta decay. The long half-life of this postulated process requires that the apparatus be extremely low in radioactive isotopes whose decays may produce backgrounds to the search. The radioassay program conducted by the collaboration to ensure that the materials comprising the apparatus are sufficiently pure is described. The resulting measurements from gamma-ray counting,more » neutron activation and mass spectroscopy of the radioactive-isotope contamination for the materials studied for use in the detector are reported. In conclusion, we interpret these numbers in the context of the expected background for the experiment.« less
The Majorana Demonstrator radioassay program
Abgrall, N.; Arnquist, I. J.; Avignone, F. T.; Back, H. O.; Barabash, A. S.; Bertrand, F. E.; Boswell, Melissa; Bradley, A. W.; Brudanin, V.; Busch, M.; Buuck, M.; Byram, D.; Caldwell, A. S.; Chan, Y. -D.; Christofferson, C. D.; Chu, Pinghan; Cuesta, C.; Detwiler, J. A.; Dunmore, J. A.; Efremenko, Yu.; Ejiri, H.; Elliott, S. R.; Finnerty, P.; Galindo-Uribarri, A.; Gehman, V. M.; Gilliss, T.; Giovanetti, G. K.; Goett, John Jerome; Green, M. P.; Gruszko, J.; Guinn, I. S.; Guiseppe, V. E.; Henning, R.; Hoppe, E. W.; Howard, S.; Howe, M. A.; Jasinski, B. R.; Johnson, R. A.; Keeter, K. J.; Kidd, M. F.; Kochetov, O.; Konovalov, S. I.; Kouzes, R. T.; LaFerriere, B. D.; Leon, J.; Loach, J. C.; MacMullin, J.; MacMullin, S.; Martin, R. D.; Massarczyk, Ralph; Meijer, S.; Mertens, S.; Miller, M. L.; Orrell, J. L.; O'Shaughnessy, C.; Overman, N. R.; Poon, A. W. P.; Pushkin, K.; Radford, D. C.; Rager, J.; Rielage, Keith Robert; Robertson, R. G. H.; Romero-Romero, E.; Ronquest, M. C.; Schubert, A. G.; Shanks, B.; Shirchenko, M.; Snavely, K. J.; Snyder, N.; Steele, D.; Suriano, A. M.; Tedeschi, D.; Trimble, J. E.; Varner, R. L.; Vasilyev, S.; Vetter, K.; Vorren, K.; White, B. R.; Wilkerson, J. F.; Wiseman, C.; Xu, W.; Yakushev, E.; Yu, C. -H.; Yumatov, V.; Zhitnikov, I.
2016-05-03
The Majorana collaboration is constructing the Majorana Demonstrator at the Sanford Underground Research Facility at the Homestake gold mine, in Lead, SD. The apparatus will use Ge detectors, enriched in isotope ^{76}Ge, to demonstrate the feasibility of a large-scale Ge detector experiment to search for neutrinoless double beta decay. The long half-life of this postulated process requires that the apparatus be extremely low in radioactive isotopes whose decays may produce backgrounds to the search. The radioassay program conducted by the collaboration to ensure that the materials comprising the apparatus are sufficiently pure is described. The resulting measurements from gamma-ray counting, neutron activation and mass spectroscopy of the radioactive-isotope contamination for the materials studied for use in the detector are reported. In conclusion, we interpret these numbers in the context of the expected background for the experiment.
Current distributions in stripe Majorana junctions
NASA Astrophysics Data System (ADS)
Osca, Javier; Llorenç, Serra
2017-02-01
We calculate current and density distributions in stripe (2D planar) junctions between normal and Majorana nanowires having a finite ( y) transverse length. In presence of a magnetic field with vertical and in-plane components, the y-symmetry of the charge current distribution in the normal lead changes strongly across the Majorana phase transition: from center-symmetric if a Majorana mode is present to laterally-shifted (as expected by the Hall effect) if the field is tilted such as to destroy the Majorana mode due to the projection rule. We compare quasi-particle and charge distributions of current and density, as well as spin magnetizations. The Majorana mode causes opposite spin accumulations on the transverse sides of the junction and the emergence of a spin current.
Helicity oscillations of Dirac and Majorana neutrinos
NASA Astrophysics Data System (ADS)
Dobrynina, Alexandra; Kartavtsev, Alexander; Raffelt, Georg
2016-06-01
The helicity of a Dirac neutrino with mass m evolves under the influence of a B field because it has a magnetic dipole moment proportional to m . Moreover, it was recently shown that a polarized or anisotropic medium engenders the same effect for both Dirac and Majorana neutrinos. Because a B field polarizes a background medium, it instigates helicity oscillations even for Majorana neutrinos unless the medium is symmetric between matter and antimatter. Motivated by these observations, we review the impact of a B field and of an anisotropic or polarized medium on helicity oscillations for Dirac and Majorana neutrinos from the common perspective of in-medium dispersion.
Signatures for Majorana neutrinos at hadron colliders.
Han, Tao; Zhang, Bin
2006-10-27
The Majorana nature of neutrinos may only be experimentally verified via lepton-number violating processes involving charged leptons. We explore the Delta L = 2 like-sign dilepton production at hadron colliders to search for signals of Majorana neutrinos. We find significant sensitivity for resonant production of a Majorana neutrino in the mass range of 10-80 GeV at the current run of the Tevatron with 2 fb(-1) integrated luminosity and in the range of 10-400 GeV at the CERN LHC with 100 fb(-1).
Majorana Fermions and Topology in Superconductors
NASA Astrophysics Data System (ADS)
Sato, Masatoshi; Fujimoto, Satoshi
2016-07-01
Topological superconductors are novel classes of quantum condensed phases, characterized by topologically nontrivial structures of Cooper pairing states. On the surfaces of samples and in vortex cores of topological superconductors, Majorana fermions, which are particles identified with their own anti-particles, appear as Bogoliubov quasiparticles. The existence and stability of Majorana fermions are ensured by bulk topological invariants constrained by the symmetries of the systems. Majorana fermions in topological superconductors obey a new type of quantum statistics referred to as non-Abelian statistics, which is distinct from bose and fermi statistics, and can be utilized for application to topological quantum computation. Also, Majorana fermions give rise to various exotic phenomena such as "fractionalization", non-local correlation, and "teleportation". A pedagogical review of these subjects is presented. We also discuss interaction effects on topological classification of superconductors, and the basic properties of Weyl superconductors.
Status of the MAJORANA DEMONSTRATOR experiment
Martin, R. D.; Abgrall, N.; Aguayo, Estanislao; Avignone, F. T.; Barabash, Alexander S.; Bertrand, F.; Boswell, M.; Brudanin, V.; Busch, Matthew; Caldwell, A. S.; Chan, Yuen-Dat; Christofferson, Cabot-Ann; Combs, Dustin C.; Detwiler, Jason A.; Doe, P. J.; Efremenko, Yuri; Egorov, Viatcheslav; Ejiri, H.; Elliott, S.; Esterline, James H.; Fast, James E.; Finnerty, P.; Fraenkle, Florian; Galindo-Uribarri, A.; Giovanetti, G. K.; Goett, J.; Green, M.; Gruszko, J.; Guiseppe, Vincente; Gusev, K.; Hallin, A. L.; Hazama, R.; Hegai, A.; Henning, R.; Hoppe, Eric W.; Howard, Stanley; Howe, M. A.; Keeter, K.; Kidd, M. F.; Kochetov, Oleg; Konovalov, S.; Kouzes, Richard T.; LaFerriere, Brian D.; Leon, Jonathan D.; Leviner, L.; Loach, J. C.; MacMullin, J.; MacMullin, S.; Mertens, S.; Mizouni, Leila; Nomachi, Masaharu; Orrell, John L.; O'Shaughnessy, Mark D.; Overman, Nicole R.; Phillips, David; Poon, Alan; Pushkin, K.; Radford, D. C.; Rielage, Keith; Robertson, R. G. H.; Romero-Romero, E.; Ronquest, M. C.; Schubert, Alexis G.; Shanks, B.; Shima, T.; Shirchenko, M.; Snavely, Kyle J.; Snyder, N.; Soin, Aleksandr; Suriano, Anne-Marie; Thompson, J.; Timkin, V.; Tornow, W.; Varner, R. L.; Vasilyev, Sergey; Vetter, Kai; Vorren, Kris R.; White, Brandon R.; Wilkerson, J. F.; Xu, W.; Yakushev, E.; Young, A.; Yu, Chang-Hong; Yumatov, Vladimir
2014-07-08
The MAJORANA DEMONSTRATOR neutrinoless double beta-decay experiment is currently under construction at the Sanford Underground Research Facility in South Dakota, USA. An overview and status of the experiment are given.
Status of the MAJORANA DEMONSTRATOR experiment
Martin, R. D.; Abgrall, N.; Chan, Y-D.; Hegai, A.; Mertens, S.; Poon, A. W. P.; Vetter, K.; Aguayo, E.; Fast, J. E.; Hoppe, E. W.; Kouzes, R. T.; LaFerriere, B. D.; Orrell, J. L.; Overman, N. R.; Soin, A.; Avignone III, F. T.; Barabash, A. S.; Konovalov, S. I.; Yumatov, V.; Bertrand, F. E.; and others
2014-06-24
The MAJORANA DEMONSTRATOR neutrinoless double beta-decay experiment is currently under construction at the Sanford Underground Research Facility in South Dakota, USA. An overview and status of the experiment are given.
Two-photon interactions with Majorana fermions
NASA Astrophysics Data System (ADS)
Latimer, David C.
2016-11-01
Because Majorana fermions are their own antiparticles, their electric and magnetic dipole moments must vanish, leaving the anapole moment as their only static electromagnetic property. But the existence of induced dipole moments is not necessarily prohibited. Through a study of real Compton scattering, we explore the constraints that the Majorana fermion's self-conjugate nature has on induced moments. In terms of the Compton amplitude, we find no constraints if the interactions are separately invariant under charge conjugation, parity, and time reversal. However, if the interactions are odd under parity and even under time reversal, then these contributions to the Compton amplitude must vanish. We employ a simple model to confirm these general findings via explicit calculation of the Majorana fermion's polarizabilities. We then use these polarizabilities to estimate the cross section for s -wave annihilation of two Majorana fermions into photons. The cross section is larger than a naive estimate might suggest.
Hunting for heavy composite Majorana neutrinos at the LHC
NASA Astrophysics Data System (ADS)
Leonardi, R.; Alunni, L.; Romeo, F.; Fanò, L.; Panella, O.
2016-11-01
We investigate the search for heavy Majorana neutrinos stemming from a composite model scenario at the upcoming LHC Run II at a centre of mass energy of 13 TeV. While previous studies of the composite Majorana neutrino were focussed on gauge interactions via magnetic type transition coupling between ordinary and heavy fermions (with mass m^*) here we complement the composite model with contact interactions at the energy scale Λ and we find that the production cross sections are dominated by such contact interactions by roughly two/three orders of magnitude. This mechanism provides therefore very interesting rates at the prospected luminosities. We study the same-sign di-lepton and di-jet signature (pp → ℓ ℓ jj) and perform a fast detector simulation based on Delphes. We compute 3σ and 5σ contour plots of the statistical significance in the parameter space (Λ ,m^*). We find that the potentially excluded regions at √{s} =13 TeV are quite larger than those excluded so far at Run I considering searches with other signatures.
Iterants, Fermions and Majorana Operators
NASA Astrophysics Data System (ADS)
Kauffman, Louis H.
Beginning with an elementary, oscillatory discrete dynamical system associated with the square root of minus one, we study both the foundations of mathematics and physics. Position and momentum do not commute in our discrete physics. Their commutator is related to the diffusion constant for a Brownian process and to the Heisenberg commutator in quantum mechanics. We take John Wheeler's idea of It from Bit as an essential clue and we rework the structure of that bit to a logical particle that is its own anti-particle, a logical Marjorana particle. This is our key example of the amphibian nature of mathematics and the external world. We show how the dynamical system for the square root of minus one is essentially the dynamics of a distinction whose self-reference leads to both the fusion algebra and the operator algebra for the Majorana Fermion. In the course of this, we develop an iterant algebra that supports all of matrix algebra and we end the essay with a discussion of the Dirac equation based on these principles.
NASA Astrophysics Data System (ADS)
Lopez, Andrew; Majorana Demonstrator Collaboration
2016-03-01
Majorana Demonstrator (MJD) is one of the major efforts of the DOE NP to demonstrate very high sensitivity for the search of the neutrino less double beta decay. The ultimate goal of MJD is to prove that background levels for a tonne-scale experiment with a similar design can be as low as 1.0 count/(4 keV*t*y). One source of background is cosmic muons that can interact in the detectors or in the shielding. In order to tag cosmic muon induced background, an efficient veto system is necessary. The MJD veto system is made out of thirty two panels of 1'' plastic scintillator. Understanding the performance of MJD veto system is vital for reducing the background count. Initial data of veto system performance during the commissioning stage will be presented. This material is based upon work supported by the U.S. Dept. of Energy, Office of Science, Office of Nuclear Physics, the Particle Astrophysics and Nuclear Physics Programs of the National Science Foundation, and the Sanford Underground Research Facility.
High voltage testing for the Majorana Demonstrator
Abgrall, N.; Arnquist, Isaac J.; Avignone, F. T.; Barabash, A.; Bertrand, F.; Bradley, A. W.; Brudanin, V.; Busch, Matthew; Buuck, M.; Byram, D.; Caldwell, A. S.; Chan, Yuen-Dat; Christofferson, C. D.; Chu, Pamela M.; Cuesta, C.; Detwiler, Jason A.; Doe, P. J.; Dunagan, C.; Efremenko, Yuri; Ejiri, H.; Elliott, S. R.; Fu, Z.; Galindo-Uribarri, A.; Giovanetti, G. K.; Goett, J.; Green, M. P.; Gruszko, J.; Guinn, I.; Guiseppe, V. E.; Henning, R.; Hoppe, Eric W.; Howard, S.; Howe, M. A.; Jasinski, B. R.; Keeter, K.; Kidd, M. F.; Konovalov, S.; Kouzes, Richard T.; Laferriere, Brian D.; Leon, Jonathan D.; Li, Alexander D.; MacMullin, J.; Martin, R. D.; Massarcyk, R.; Meijer, S. J.; Mertens, S.; Orrell, John L.; O'Shaughnessy, C.; Poon, Alan W.; Radford, D. C.; Rager, J.; Rielage, Keith; Robertson, R. G. H.; Romero Romo, M.; Shanks, B.; Shirchenko, M.; Snyder, N.; Suriano, Anne-Marie E.; Tedeschi, D.; Thompson, Andrew; Ton, K. T.; Trimble, J. E.; Varner, R. L.; Vasilyev, Sergey; Vetter, Kai; Vorren, Kris R.; White, Brandon R.; Wilkerson, J. F.; Wiseman, C.; Xu, W.; Yakushev, E.; Yu, Chang-Hong; Yumatov, V.
2016-07-01
The Majorana Collaboration is constructing theMajorana Demonstrator, an ultra-low background, 44-kg modular high-purity Ge (HPGe) detector array to search for neutrinoless double-beta decay in 76Ge. The phenomenon of surface micro-discharge induced by high-voltage has been studied in the context of theMajorana Demonstrator. This effect can damage the front-end electronics or mimic detector signals. To ensure the correct performance, every high-voltage cable and feedthrough must be capable of supplying HPGe detector operating voltages as high as 5 kV without exhibiting discharge. R&D measurements were carried out to understand the testing system and determine the optimum design configuration of the high-voltage path, including different improvements of the cable layout and feedthrough flange model selection. Every cable and feedthrough to be used at the Majorana Demonstrator was characterized and the micro-discharge effects during theMajorana Demonstrator commissioning phase were studied. A stable configuration has been achieved, and the cables and connectors can supply HPGe detector operating voltages without exhibiting discharge.
High voltage testing for the MAJORANA DEMONSTRATOR
NASA Astrophysics Data System (ADS)
Abgrall, N.; Arnquist, I. J.; Avignone, F. T.; Barabash, A. S.; Bertrand, F. E.; Bradley, A. W.; Brudanin, V.; Busch, M.; Buuck, M.; Byram, D.; Caldwell, A. S.; Chan, Y.-D.; Christofferson, C. D.; Chu, P.-H.; Cuesta, C.; Detwiler, J. A.; Doe, P. J.; Dunagan, C.; Efremenko, Yu.; Ejiri, H.; Elliott, S. R.; Fu, Z.; Galindo-Uribarri, A.; Giovanetti, G. K.; Goett, J.; Green, M. P.; Gruszko, J.; Guinn, I. S.; Guiseppe, V. E.; Henning, R.; Hoppe, E. W.; Howard, S.; Howe, M. A.; Jasinski, B. R.; Keeter, K. J.; Kidd, M. F.; Konovalov, S. I.; Kouzes, R. T.; LaFerriere, B. D.; Leon, J.; Li, A.; MacMullin, J.; Martin, R. D.; Massarczyk, R.; Meijer, S. J.; Mertens, S.; Orrell, J. L.; O'Shaughnessy, C.; Poon, A. W. P.; Radford, D. C.; Rager, J.; Rielage, K.; Robertson, R. G. H.; Romero-Romero, E.; Shanks, B.; Shirchenko, M.; Snyder, N.; Suriano, A. M.; Tedeschi, D.; Thompson, A.; Ton, K. T.; Trimble, J. E.; Varner, R. L.; Vasilyev, S.; Vetter, K.; Vorren, K.; White, B. R.; Wilkerson, J. F.; Wiseman, C.; Xu, W.; Yakushev, E.; Yu, C.-H.; Yumatov, V.
2016-07-01
The MAJORANA Collaboration is constructing the MAJORANA DEMONSTRATOR, an ultra-low background, 44-kg modular high-purity Ge (HPGe) detector array to search for neutrinoless double-beta decay in 76Ge. The phenomenon of surface micro-discharge induced by high-voltage has been studied in the context of the MAJORANA DEMONSTRATOR. This effect can damage the front-end electronics or mimic detector signals. To ensure the correct performance, every high-voltage cable and feedthrough must be capable of supplying HPGe detector operating voltages as high as 5 kV without exhibiting discharge. R&D measurements were carried out to understand the testing system and determine the optimum design configuration of the high-voltage path, including different improvements of the cable layout and feedthrough flange model selection. Every cable and feedthrough to be used at the MAJORANA DEMONSTRATOR was characterized and the micro-discharge effects during the MAJORANA DEMONSTRATOR commissioning phase were studied. A stable configuration has been achieved, and the cables and connectors can supply HPGe detector operating voltages without exhibiting discharge.
High voltage testing for the Majorana Demonstrator
Abgrall, N.; Arnquist, I. J.; Avignone, III, F. T.; Barabash, A. S.; Bertrand, F. E.; Bradley, A. W.; Brudanin, V.; Busch, M.; Buuck, M.; Byram, D.; Caldwell, A. S.; Chan, Y. -D.; Christofferson, C. D.; Chu, P. -H.; Cuesta, C.; Detwiler, J. A.; Doe, P. J.; Dunagan, C.; Efremenko, Yu.; Ejiri, H.; Elliot, S. R.; Fu, Z.; Galindo-Uribarri, A.; Giovanetti, G. K.; Goett, J.; Green, M. P.; Gruszko, J.; Guinn, I. S.; Guiseppe, V. E.; Henning, R.; Hoppe, E. W.; Howard, S.; Howe, M. A.; Jasinski, B. R.; Keeter, K. J.; Kidd, M. F.; Konovalov, S. I.; Kouzes, R. T.; LaFerriere, B. D.; Leon, J.; Li, A.; MacMullin, J.; Martin, R. D.; Massarczyk, R.; Meijer, S. J.; Mertens, S.; Orrell, J. L.; O'Shaughnessy, C.; Poon, A. W. P.; Radford, D. C.; Rager, J.; Rielage, K.; Robertson, R. G. H.; Romero-Romero, E.; Shanks, B.; Shirchenko, M.; Snyder, N.; Suriano, A. M.; Tedeschi, D.; Thompson, A.; Ton, K. T.; Trimble, J. E.; Varner, R. L.; Vasilyev, S.; Vetter, K.; Vorren, K.; White, B. R.; Wilkerson, J. F.; Wiseman, C.; Xu, W.; Yakushev, E.; Yu, C. -H.; Yumatov, V.
2016-04-04
The Majorana Collaboration is constructing the Majorana Demonstrator, an ultra-low background, 44-kg modular high-purity Ge (HPGe) detector array to search for neutrinoless double-beta decay in ^{76}Ge. The phenomenon of surface micro-discharge induced by high-voltage has been studied in the context of the Majorana Demonstrator. This effect can damage the front-end electronics or mimic detector signals. To ensure the correct performance, every high-voltage cable and feedthrough must be capable of supplying HPGe detector operating voltages as high as 5 kV without exhibiting discharge. R&D measurements were carried out to understand the testing system and determine the optimum design configuration of the high-voltage path, including different improvements of the cable layout and feedthrough flange model selection. Every cable and feedthrough to be used at the Majorana Demonstrator was characterized and the micro-discharge effects during the Majorana Demonstrator commissioning phase were studied. Furthermore, a stable configuration has been achieved, and the cables and connectors can supply HPGe detector operating voltages without exhibiting discharge.
High voltage testing for the Majorana Demonstrator
Abgrall, N.; Arnquist, I. J.; Avignone, III, F. T.; ...
2016-04-04
The Majorana Collaboration is constructing the Majorana Demonstrator, an ultra-low background, 44-kg modular high-purity Ge (HPGe) detector array to search for neutrinoless double-beta decay in 76Ge. The phenomenon of surface micro-discharge induced by high-voltage has been studied in the context of the Majorana Demonstrator. This effect can damage the front-end electronics or mimic detector signals. To ensure the correct performance, every high-voltage cable and feedthrough must be capable of supplying HPGe detector operating voltages as high as 5 kV without exhibiting discharge. R&D measurements were carried out to understand the testing system and determine the optimum design configuration of themore » high-voltage path, including different improvements of the cable layout and feedthrough flange model selection. Every cable and feedthrough to be used at the Majorana Demonstrator was characterized and the micro-discharge effects during the Majorana Demonstrator commissioning phase were studied. Furthermore, a stable configuration has been achieved, and the cables and connectors can supply HPGe detector operating voltages without exhibiting discharge.« less
THE MAJORANA DEMONSTRATOR: OVERVIEW AND STATUS UPDATE
Keeter, K.; Abgrall, N.; Aguayo, Estanislao; Avignone, F. T.; Barabash, Alexander; Bertrand, F.; Boswell, M.; Brudanin, V.; Busch, Matthew; Caldwell, A. S.; Chan, Yuen-Dat; Christofferson, Cabot-Ann; Combs, Dustin C.; Cuesta, C.; Detwiler, Jason A.; Doe, Peter J.; Efremenko, Yuri; Egorov, Viatcheslav; Ejiri, H.; Elliott, S.; Esterline, James H.; Fast, James E.; Finnerty, P.; Fraenkle, Florian; Galindo-Uribarri, A.; Giovanetti, G. K.; Goett, J.; Green, Matthew P.; Gruszko, J.; Guiseppe, Vincente; Gusev, K.; Hallin, A. L.; Hazama, R.; Hegai, A.; Henning, Reyco; Hoppe, Eric W.; Howard, Stanley; Howe, M. A.; Kidd, M. F.; Kochetov, Oleg; Konovalov, S.; Kouzes, Richard T.; LaFerriere, Brian D.; Leon, Jonathan D.; Leviner, L.; Loach, J. C.; MacMullin, S.; Martin, R. D.; Mertens, S.; Mizouni, Leila; Nomachi, Masaharu; O'Shaughnessy, Mark D.; Orrell, John L.; Overman, Nicole R.; Phillips, D.; Poon, Alan; Pushkin, K.; Radford, D. C.; Rielage, Keith; Robertson, R. G. H.; Ronquest, M. C.; Schubert, Alexis G.; Shanks, B.; Shima, T.; Shirchenko, M.; Snavely, Kyle J.; Snyder, N.; Soin, Aleksandr; Strain, J.; Suriano, Anne-Marie; Swift, Gary; Thompson, J.; Timkin, V.; Tornow, Werner; Varner, R. L.; Vasilyev, Sergey; Vetter, Kai; Vorren, Kris R.; White, Brandon R.; Wilkerson, J. F.; Wiseman, C.; Xu, W.; Yakushev, E.; Young, A.; Yu, Chang-Hong; Yumatov, Vladimir
2013-04-12
The MAJORANA DEMONSTRATOR is being constructed at the Sanford Underground Research Facility (SURF) in Lead, SD by the MAJORANA Collaboration to demonstrate the feasibility of a tonne-scale neutrinoless double beta decay experiment based on 76Ge. The observation of neutrinoless double beta decay would indicate that neutrinos can serve as their own antiparticles, thus proving neutrinos to be Majorana particles, and would give information on neutrino masses. Attaining sensitivities for neutrino masses in the inverted hierarchy region requires large tonne-scale detectors with extremely low backgrounds. The DEMONSTRATOR project will show that sufficiently low backgrounds are achievable. A brief description of the detector and a status update on the construction will be given, including the work done at BHSU on acid-etching of Pb shielding bricks.
MAJORANA Collaboration's Experience with Germanium Detectors
Mertens, S.; Abgrall, N.; Avignone, III, F. T.; Bertrand, F. E.; Efremenko, Yuri; Galindo-Uribarri, A; Radford, D. C.; Romero-Romero, E.; White, B. R.; Wilkerson, J. F.; Majorana,
2015-01-01
The goal of the Majorana Demonstrator project is to search for 0v beta beta decay in Ge-76. Of all candidate isotopes for 0v beta beta, Ge-76 has some of the most favorable characteristics. Germanium detectors are a well established technology, and in searches for 0v beta beta, the high purity germanium crystal acts simultaneously as source and detector. Furthermore, p-type germanium detectors provide excellent energy resolution and a specially designed point contact geometry allows for sensitive pulse shape discrimination. This paper will summarize the experiences the MAJORANA collaboration made with enriched germanium detectors manufactured by ORTEC (R)(R). The process from production, to characterization and integration in MAJORANA mounting structure will be described. A summary of the performance of all enriched germanium detectors will be given.
MAJORANA Collaboration's experience with germanium detectors
Mertens, S.; Abgrall, N.; Avignone, F. T.; Barabash, A. S.; Bertrand, F. E.; Brudanin, V.; Busch, M.; Buuck, M.; Byram, D.; Caldwell, A. S.; Chan, Y. -D.; Christofferson, C. D.; Cuesta, C.; Detwiler, J. A.; Efremenko, Yu; Ejiri, H.; Elliott, S. R.; Galindo-Uribarri, A.; Giovanetti, G. K.; Goett, J.; Green, M. P.; Gruszko, J.; Guinn, I.; Guiseppe, V. E.; Henning, R.; Hoppe, E. W.; Howard, S.; Howe, M. A.; Jasinski, B. R.; Keeter, K. J.; Kidd, M. F.; Konovalov, S. I.; Kouzes, R. T.; LaFerriere, B. D.; Leon, J.; MacMullin, J.; Martin, R. D.; Meijer, S. J.; Orrell, J. L.; O'Shaughnessy, C.; Overman, N. R.; Poon, A. W. P.; Radford, D. C.; Rager, J.; Rielage, K.; Robertson, R. G. H.; Romero-Romero, E.; Ronquest, M. C.; Shanks, B.; Shirchenko, M.; Snyder, N.; Tedeschi, D.; Trimble, J. E.; Varner, R. L.; Vasilyev, S.; Vetter, K.; Vorren, K.; White, B. R.; Wilkerson, J. F.; Wiseman, C.; Xu, W.; Yakushev, E.; Yu, C. -H.; Yumatov, V.
2015-05-01
The goal of the Majorana Demonstrator project is to search for 0νββ decay in ^{76}Ge. Of all candidate isotopes for 0νββ, ^{76}Ge has some of the most favorable characteristics. Germanium detectors are a well established technology, and in searches for 0νββ, the high purity germanium crystal acts simultaneously as source and detector. Furthermore, p-type germanium detectors provide excellent energy resolution and a specially designed point contact geometry allows for sensitive pulse shape discrimination. This paper will summarize the experiences the MAJORANA collaboration made with enriched germanium detectors manufactured by ORTEC®®. The process from production, to characterization and integration in MAJORANA mounting structure will be described. A summary of the performance of all enriched germanium detectors will be given.
Majorana quasiparticles of an inhomogeneous Rashba chain
NASA Astrophysics Data System (ADS)
Maśka, Maciej M.; Gorczyca-Goraj, Anna; Tworzydło, Jakub; Domański, Tadeusz
2017-01-01
We investigate the inhomogeneous Rashba chain coupled to a superconducting substrate, hosting the Majorana quasiparticles near its edges. We discuss its subgap spectrum and study how robust the zero-energy quasiparticles are against the diagonal and off-diagonal disorder. Studying the Z2 topological invariant we show that disorder-induced transition from the topologically nontrivial to trivial phases is manifested by characteristic features in the spatially resolved quasiparticle spectrum at zero energy. We provide evidence for the nonlocal nature of the zero-energy Majorana quasiparticles that are well preserved upon partitioning the chain into separate pieces. Even though the Majorana quasiparticles are not completely immune to inhomogeneity, we show that they can spread onto other (normal) nanoscopic objects via the proximity effect.
The Majorana Neutrinoless Double-beta Decay Experiment
NASA Astrophysics Data System (ADS)
Guiseppe, Vincente
2008-04-01
Neutrinoless double-beta decay searches play a major role in determining the effective Majorana neutrino mass, the Majorana nature of neutrinos, and a lepton violating process. The Majorana experiment proposes to assemble an array of HPGe detectors to search for neutrinoless double-beta decay in ^76Ge. Initially, Majorana aims to construct a prototype system containing 60 kg of Ge detectors to demonstrate the potential of a future 1-tonne experiment. The design and potential reach of the prototype system will be presented. This talk will also discuss material purity, detector optimization, background rejection, identification of rare backgrounds, and other key technologies to be utilized in the Majorana experiment.
Spin and Majorana polarization in topological superconducting wires.
Sticlet, Doru; Bena, Cristina; Simon, Pascal
2012-03-02
We study a one-dimensional wire with strong Rashba and Dresselhaus spin-orbit coupling (SOC), which supports Majorana fermions when subject to a Zeeman magnetic field and in the proximity of a superconductor. Using both analytical and numerical techniques we calculate the electronic spin texture of the Majorana end states. We find that the spin polarization of these states depends on the relative magnitude of the Rashba and Dresselhaus SOC components. Moreover, we define and calculate a local "Majorana polarization" and "Majorana density" and argue that they can be used as order parameters to characterize the topological transition between the trivial system and the system exhibiting Majorana bound modes. We find that the local Majorana polarization is correlated to the transverse spin polarization, and we propose to test the presence of Majorana fermions in a 1D system by a spin-polarized density of states measurement.
Majorana Fermions in Chiral Topological Ferromagnetic Nanowires
NASA Astrophysics Data System (ADS)
Dumitrescu, Eugen; Roberts, Brenden; Tewari, Sumanta; Sau, Jay D.
2015-03-01
Motivated by a recent experiment in which zero-bias peaks have been observed in STM experiments performed on chains of magnetic atoms on a superconductor, we show that a multichannel ferromagnetic wire deposited on a spin-orbit coupled superconducting substrate can realize a non-trivial chiral topological superconducting state with Majorana bound states localized at the wire ends. The non-trivial topological state occurs for generic parameters requiring no fine tuning, at least for very large exchange spin splitting in the wire. We theoretically obtain the signatures which appear in the presence of an arbitrary number of Majorana modes in multi-wire systems incorporating the role of finite temperature, finite potential barrier at the STM tip, and finite wire length. These signatures are presented in terms of spatial profiles of STM differential conductance which clearly reveal zero energy Majorana end modes and the prediction of a multiple Majorana based fractional Josephson effect. Co-author: S. Das Sarma. Work supported by AFOSR (FA9550-13-1-0045) at Clemson University and by LPS-CMTC and JQI-NSF-PFC at the University of Maryland.
Odd frequency pairing of interacting Majorana fermions
NASA Astrophysics Data System (ADS)
Huang, Zhoushen; Woelfle, Peter; Balatsky, Alexandar
Majorana fermions are rising as a promising key component in quantum computation. While the prevalent approach is to use a quadratic (i.e. non-interacting) Majorana Hamiltonian, when expressed in terms of Dirac fermions, generically the Hamiltonian involves interaction terms. Here we focus on the possible pair correlations in a simple model system. We study a model of Majorana fermions coupled to a boson mode and show that the anomalous correlator between different Majorana fermions, located at opposite ends of a topological wire, exhibits odd frequency behavior. It is stabilized when the coupling strength g is above a critical value gc. We use both, conventional diagrammatic theory and a functional integral approach, to derive the gap equation, the critical temperature, the gap function, the critical coupling, and a Ginzburg-Landau theory allowing to discuss a possible subleading admixture of even-frequency pairing. Work supported by USDOE DE-AC52-06NA25396 E304, Knut and Alice Wallenberg Foundation, and ERC DM-321031.
Robust signatures detection of Majorana fermions in superconducting iron chains
Chen, Hua-Jun; Fang, Xian-Wen; Chen, Chang-Zhao; Li, Yang; Tang, Xu-Dong
2016-01-01
We theoretically propose an optical means to detect Majorana fermions in superconducting iron (Fe) chains with a hybrid quantum dot-nanomechanical resonator system driven by two-tone fields, which is very different from the current tunneling spectroscopy experiments with electrical means. Based on the scheme, the phenomenon of Majorana modes induced transparency is demonstrated and a straightforward method to determine the quantum dot-Majorana fermions coupling strength is also presented. We further investigate the role of the nanomechanical resonator, and the resonator behaving as a phonon cavity enhances the exciton resonance spectrum, which is robust for detecting of Majorana fermions. The coherent optical spectrum affords a potential supplement to detecte Majorana fermions and supports Majorana fermions-based topological quantum computation in superconducting iron chains. PMID:27857149
Robust signatures detection of Majorana fermions in superconducting iron chains
NASA Astrophysics Data System (ADS)
Chen, Hua-Jun; Fang, Xian-Wen; Chen, Chang-Zhao; Li, Yang; Tang, Xu-Dong
2016-11-01
We theoretically propose an optical means to detect Majorana fermions in superconducting iron (Fe) chains with a hybrid quantum dot-nanomechanical resonator system driven by two-tone fields, which is very different from the current tunneling spectroscopy experiments with electrical means. Based on the scheme, the phenomenon of Majorana modes induced transparency is demonstrated and a straightforward method to determine the quantum dot-Majorana fermions coupling strength is also presented. We further investigate the role of the nanomechanical resonator, and the resonator behaving as a phonon cavity enhances the exciton resonance spectrum, which is robust for detecting of Majorana fermions. The coherent optical spectrum affords a potential supplement to detecte Majorana fermions and supports Majorana fermions-based topological quantum computation in superconducting iron chains.
Background model for the Majorana Demonstrator
Cuesta, C.; Abgrall, N.; Aguayo, E.; ...
2015-01-01
The Majorana Collaboration is constructing a system containing 40 kg of HPGe detectors to demonstrate the feasibility and potential of a future tonne-scale experiment capable of probing the neutrino mass scale in the inverted-hierarchy region. To realize this, a major goal of the Majorana Demonstrator is to demonstrate a path forward to achieving a background rate at or below 1 cnt/(ROI-t-y) in the 4 keV region of interest around the Q-value at 2039 keV. This goal is pursued through a combination of a significant reduction of radioactive impurities in construction materials with analytical methods for background rejection, for example usingmore » powerful pulse shape analysis techniques profiting from the p-type point contact HPGe detectors technology. The effectiveness of these methods is assessed using simulations of the different background components whose purity levels are constrained from radioassay measurements.« less
Background model for the Majorana Demonstrator
Cuesta, C.; Abgrall, N.; Aguayo, E.; Avignone, III, F. T.; Barabash, A. S.; Bertrand, F. E.; Boswell, M.; Brudanin, V.; Busch, M.; Byram, D.; Caldwell, A. S.; Chan, Y -D.; Christofferson, C. D.; Combs, D. C.; Detwiler, J. A.; Doe, P. J.; Efremenko, Yu.; Egorov, V.; Ejiri, H.; Elliott, S. R.; Fast, J. E.; Finnerty, P.; Fraenkle, F. M.; Galindo-Uribarri, A.; Giovanetti, G. K.; Goett, J.; Green, M. P.; Gruszko, J.; Guiseppe, V.; Gusev, K.; Hallin, A.; Hazama, R.; Hegai, A.; Henning, R.; Hoppe, E. W.; Howard, S.; Howe, M. A.; Keeter, K. J.; Kidd, M. F.; Kochetov, O.; Konovalov, S. I.; Kouzes, R. T.; LaFerriere, B. D.; Leon, J.; Leviner, L. E.; Loach, J. C.; MacMullin, J.; MacMullin, S.; Martin, R. D.; Meijer, S.; Mertens, S.; Nomachi, M.; Orrell, J. L.; O'Shaughnessy, C.; Overman, N. R.; Phillips, D. G.; Poon, W. W. P.; Pushkin, K.; Radford, D. C.; Rager, J.; Rielage, K.; Robertson, R. G. H.; Romero-Romero, E.; Ronquest, M. C.; Schubert, A. G.; Shanks, B.; Shima, T.; Shirchenko, M.; Snavely, K. K.; Snyder, N.; Suriano, A. M.; Thompson, J.; Timkin, V.; Tornow, W.; Trimble, J. E.; Varner, R.; Vasilyev, S.; Vetter, K.; Vorren, K.; White, B.; Wilkerson, J. F.; Wiseman, C.; Xu, W.; Yakushev, E.; Young, A. R.; Yu, C. -H.; Yumatov, V.
2015-01-01
The Majorana Collaboration is constructing a system containing 40 kg of HPGe detectors to demonstrate the feasibility and potential of a future tonne-scale experiment capable of probing the neutrino mass scale in the inverted-hierarchy region. To realize this, a major goal of the Majorana Demonstrator is to demonstrate a path forward to achieving a background rate at or below 1 cnt/(ROI-t-y) in the 4 keV region of interest around the Q-value at 2039 keV. This goal is pursued through a combination of a significant reduction of radioactive impurities in construction materials with analytical methods for background rejection, for example using powerful pulse shape analysis techniques profiting from the p-type point contact HPGe detectors technology. The effectiveness of these methods is assessed using simulations of the different background components whose purity levels are constrained from radioassay measurements.
First data of the MAJORANA DEMONSTRATOR
NASA Astrophysics Data System (ADS)
Cuesta, Clara; Majorana Collaboration
2016-09-01
The MAJORANA Collaboration is constructing a system containing 44 kg of HPGe detectors to demonstrate the feasibility and potential of a future tonne-scale experiment capable of probing the neutrino mass scale in the inverted-hierarchy region. To realize this, a major goal of MAJORANA DEMONSTRATOR is to demonstrate a path forward to achieving a background rate at or below 1 cnt/(ROI-t-y) in the 4 keV region of interest around the Q-value at 2039 keV. This goal is pursued through a combination of a significant reduction of radioactive impurities in construction materials with analytical methods for background rejection. The analysis tools are based on run ranking, data reduction, pulse shape analysis, event coincidences, and time correlations. The first data corresponding to the commissioning of the DEMONSTRATOR analyzed using these techniques will be presented. The cuts developed to reject delayed charge recovery and multisite events will be described.
Majorana fermions in noisy Kitaev wires
NASA Astrophysics Data System (ADS)
Hu, Ying; Cai, Zi; Baranov, Mikhail A.; Zoller, Peter
2015-10-01
Robustness of edge states and non-Abelian excitations of topological states of matter promises quantum memory and quantum processing, which are naturally immune to microscopic imperfections such as static disorder. However, topological properties will not in general protect quantum systems from time-dependent disorder or noise. Here we take the example of a network of Kitaev wires with Majorana edge modes storing qubits to investigate the effects of classical noise in the crossover from the quasistatic to the fast fluctuation regime. We present detailed results for the Majorana edge correlations, and fidelity of braiding operations for both global and local noise sources preserving parity symmetry, such as random chemical potentials and phase fluctuations. While in general noise will induce heating and dephasing, we identify examples of long-lived quantum correlations in the presence of fast noise due to motional narrowing, where external noise drives the system rapidly between the topological and nontopological phases.
MAJORANA Collaboration's experience with germanium detectors
Mertens, S.; Abgrall, N.; Avignone, F. T.; ...
2015-05-01
The goal of the Majorana Demonstrator project is to search for 0νββ decay in 76Ge. Of all candidate isotopes for 0νββ, 76Ge has some of the most favorable characteristics. Germanium detectors are a well established technology, and in searches for 0νββ, the high purity germanium crystal acts simultaneously as source and detector. Furthermore, p-type germanium detectors provide excellent energy resolution and a specially designed point contact geometry allows for sensitive pulse shape discrimination. This paper will summarize the experiences the MAJORANA collaboration made with enriched germanium detectors manufactured by ORTEC®®. The process from production, to characterization and integration in MAJORANAmore » mounting structure will be described. A summary of the performance of all enriched germanium detectors will be given.« less
Milestones Toward Majorana-Based Quantum Computing
NASA Astrophysics Data System (ADS)
Aasen, David; Hell, Michael; Mishmash, Ryan V.; Higginbotham, Andrew; Danon, Jeroen; Leijnse, Martin; Jespersen, Thomas S.; Folk, Joshua A.; Marcus, Charles M.; Flensberg, Karsten; Alicea, Jason
2016-07-01
We introduce a scheme for preparation, manipulation, and read out of Majorana zero modes in semiconducting wires with mesoscopic superconducting islands. Our approach synthesizes recent advances in materials growth with tools commonly used in quantum-dot experiments, including gate control of tunnel barriers and Coulomb effects, charge sensing, and charge pumping. We outline a sequence of milestones interpolating between zero-mode detection and quantum computing that includes (1) detection of fusion rules for non-Abelian anyons using either proximal charge sensors or pumped current, (2) validation of a prototype topological qubit, and (3) demonstration of non-Abelian statistics by braiding in a branched geometry. The first two milestones require only a single wire with two islands, and additionally enable sensitive measurements of the system's excitation gap, quasiparticle poisoning rates, residual Majorana zero-mode splittings, and topological-qubit coherence times. These pre-braiding experiments can be adapted to other manipulation and read out schemes as well.
Physics of Majorana modes in interacting helical liquid
Sarkar, Sujit
2016-01-01
As an attempt to understand and search for the existence of Majorana zero mode, we study the topological quantum phase transition and also the nature of this transition in helical liquid system, which appears in different physical systems. We present Majorana-Ising transition along with the phase boundary in the presence of interaction. We show the appearance of Majorana mode under the renormalization of the parameters of the system and also the topological protection of it. We present the length scale dependent condition for the appearance of Majorana edge state and also the absence of edge state for a certain regime of parameter space. PMID:27460508
The τ neutrino as a Majorana particle
NASA Astrophysics Data System (ADS)
Carena, M.; Lampe, B.; Wagner, C. E. M.
1993-11-01
A Majorana mass term for the τ neutrino would induce neutrino-antineutrino mixing and thereby a process which violates fermion number by two units. We study the possibility of distinguishing between a massive Majorana and a Dirac τ neutrino, by measuring fermion number violating processes in a deep inelastic scattering experiment νp→ τX. We show that, if the neutrino beam is obtained from the decay of high energetic pions, the probability of obtaining “wrong sign” τ leptons is suppressed by a factor O( mντ2θ2/ mμ2) instead of the naively expected suppression factor θ2mντ2/ Eν2, where E ν is the τ neutrino energy, mντ and mμ are the τ neutrino and muon masses, respectively, and θ is the ν μ-ν τ mixing angle. If mντ is of the order of 10 MeV and θ is of the order of 0.01-0.04 (the present bounds are ( mντ < 35 MeV, θ < 0.04) the next round of experiments may be able to distinguish between Majorana and Dirac τ neutrinos.
Majorana zero modes in spintronics devices
NASA Astrophysics Data System (ADS)
Wu, Chien-Te; Anderson, Brandon M.; Hsiao, Wei-Han; Levin, K.
2017-01-01
We show that topological phases should be realizable in readily available and well-studied heterostructures. In particular we identify a new class of topological materials which are well known in spintronics: helical ferromagnet-superconducting junctions. We note that almost all previous work on topological heterostructures has focused on creating Majorana modes at the proximity interface in effectively two-dimensional or one-dimensional systems. The particular heterostructures we address exhibit finite-range proximity effects leading to nodal superconductors with Majorana modes localized well away from this interface. To show this, we implement a Bogoliubov-de Gennes (BdG) proximity numerical scheme, which importantly involves two finite dimensions in a three-dimensional junction. Incorporating this level of numerical complexity serves to distinguish ours from alternative numerical BdG approaches which are limited by generally assuming translational invariance or periodic boundary conditions along multiple directions. With this access to the edges, we are then able to illustrate in a concrete fashion the wave functions of Majorana zero modes and, moreover, address finite-size effects. In the process we establish consistency with a simple analytical model.
Search for heavy Majorana neutrinos with the ATLAS detector in pp collisions at √s = 8 TeV
Aad, G.
2015-07-29
A search for heavy Majorana neutrinos in events containing a pair of high-p_{T} leptons of the same charge and high-p_{T} jets is presented. The search uses 20.3 fb^{-1} of pp collision data collected with the ATLAS detector at the CERN Large Hadron Collider with a centre-of-mass energy of √s = 8 TeV. The data are found to be consistent with the background-only hypothesis based on the Standard Model expectation. In the context of a Type-I seesaw mechanism, limits are set on the production cross-section times branching ratio for production of heavy Majorana neutrinos in the mass range between 100 and 500 GeV. The limits are subsequently interpreted as limits on the mixing between the heavy Majorana neutrinos and the Standard Model neutrinos. In the context of a left-right symmetric model, limits on the production cross-section times branching ratio are set with respect to the masses of heavy Majorana neutrinos and heavy gauge bosons W_{R} and Z'.
Search for heavy Majorana neutrinos with the ATLAS detector in pp collisions at √s = 8 TeV
Aad, G.
2015-07-29
A search for heavy Majorana neutrinos in events containing a pair of high-pT leptons of the same charge and high-pT jets is presented. The search uses 20.3 fb-1 of pp collision data collected with the ATLAS detector at the CERN Large Hadron Collider with a centre-of-mass energy of √s = 8 TeV. The data are found to be consistent with the background-only hypothesis based on the Standard Model expectation. In the context of a Type-I seesaw mechanism, limits are set on the production cross-section times branching ratio for production of heavy Majorana neutrinos in the mass range between 100 andmore » 500 GeV. The limits are subsequently interpreted as limits on the mixing between the heavy Majorana neutrinos and the Standard Model neutrinos. In the context of a left-right symmetric model, limits on the production cross-section times branching ratio are set with respect to the masses of heavy Majorana neutrinos and heavy gauge bosons WR and Z'.« less
Three-dimensional Majorana fermions in chiral superconductors.
Kozii, Vladyslav; Venderbos, Jörn W F; Fu, Liang
2016-12-01
Using a systematic symmetry and topology analysis, we establish that three-dimensional chiral superconductors with strong spin-orbit coupling and odd-parity pairing generically host low-energy nodal quasiparticles that are spin-nondegenerate and realize Majorana fermions in three dimensions. By examining all types of chiral Cooper pairs with total angular momentum J formed by Bloch electrons with angular momentum j in crystals, we obtain a comprehensive classification of gapless Majorana quasiparticles in terms of energy-momentum relation and location on the Fermi surface. We show that the existence of bulk Majorana fermions in the vicinity of spin-selective point nodes is rooted in the nonunitary nature of chiral pairing in spin-orbit-coupled superconductors. We address experimental signatures of Majorana fermions and find that the nuclear magnetic resonance spin relaxation rate is significantly suppressed for nuclear spins polarized along the nodal direction as a consequence of the spin-selective Majorana nature of nodal quasiparticles. Furthermore, Majorana nodes in the bulk have nontrivial topology and imply the presence of Majorana bound states on the surface, which form arcs in momentum space. We conclude by proposing the heavy fermion superconductor PrOs4Sb12 and related materials as promising candidates for nonunitary chiral superconductors hosting three-dimensional Majorana fermions.
Three-dimensional Majorana fermions in chiral superconductors
Kozii, Vladyslav; Venderbos, Jörn W. F.; Fu, Liang
2016-01-01
Using a systematic symmetry and topology analysis, we establish that three-dimensional chiral superconductors with strong spin-orbit coupling and odd-parity pairing generically host low-energy nodal quasiparticles that are spin-nondegenerate and realize Majorana fermions in three dimensions. By examining all types of chiral Cooper pairs with total angular momentum J formed by Bloch electrons with angular momentum j in crystals, we obtain a comprehensive classification of gapless Majorana quasiparticles in terms of energy-momentum relation and location on the Fermi surface. We show that the existence of bulk Majorana fermions in the vicinity of spin-selective point nodes is rooted in the nonunitary nature of chiral pairing in spin-orbit–coupled superconductors. We address experimental signatures of Majorana fermions and find that the nuclear magnetic resonance spin relaxation rate is significantly suppressed for nuclear spins polarized along the nodal direction as a consequence of the spin-selective Majorana nature of nodal quasiparticles. Furthermore, Majorana nodes in the bulk have nontrivial topology and imply the presence of Majorana bound states on the surface, which form arcs in momentum space. We conclude by proposing the heavy fermion superconductor PrOs4Sb12 and related materials as promising candidates for nonunitary chiral superconductors hosting three-dimensional Majorana fermions. PMID:27957543
Comments on a Paper by Majorana Concerning Elementary Particles
NASA Astrophysics Data System (ADS)
Fradkin, David M.
2006-05-01
An early paper (1932) by Majorana, that has received but scant attention, is reexamined in light of later developments. This pioneering paper constructs a relativistically invariant theory of arbitrary spin particles, develops and utilizes infinite dimensional representations of the homogeneous Lorentz group, and provides a mass spectrum for elementary particles. The relevance of Majorana's approach and results to later and current research is explained. "Reprinted with permission from the AMERICAN JOURNAL OF PHYSICS, Volume 34, Issue 4, pp. 314-318. Copyright 1966, American Association of Physics Teachers" We reproduce here the historical D. M. Fradkin 1966 paper whose role among the physicists of high energy was decisive; since then espressions like "Majorana mass", "Majorana spinors" and "Majorana neutrino" have become usual. The paper is based upon the work Teoria di Particelle con Momento Intrinseco Arbitrario, translated by Italiam from Edoardo Amaldi. Ignazio Licata
Universal quantum computation with hybrid spin-Majorana qubits
NASA Astrophysics Data System (ADS)
Hoffman, Silas; Schrade, Constantin; Klinovaja, Jelena; Loss, Daniel
2016-07-01
We theoretically propose a set of universal quantum gates acting on a hybrid qubit formed by coupling a quantum-dot spin qubit and Majorana fermion qubit. First, we consider a quantum dot that is tunnel coupled to two topological superconductors. The effective spin-Majorana exchange facilitates a hybrid cnot gate for which either qubit can be the control or target. The second setup is a modular scalable network of topological superconductors and quantum dots. As a result of the exchange interaction between adjacent spin qubits, a cnot gate is implemented that acts on neighboring Majorana qubits and eliminates the necessity of interqubit braiding. In both setups, the spin-Majorana exchange interaction allows for a phase gate, acting on either the spin or the Majorana qubit, and for a swap or hybrid swap gate which is sufficient for universal quantum computation without projective measurements.
Interferometric resonance signatures of Majorana bound states
NASA Astrophysics Data System (ADS)
Golub, Anatoly; Horovitz, Baruch
2015-07-01
We calculate the current noise power spectrum in a nanoscopic interferometer consisting of a Majorana bound state (MBS) and a localized spin. We show that for large voltage (though less than the superconducting gap) several strong resonance peaks appear at frequencies that depend on the Zeeman splitting of the localized spin and on its tunneling to the localized spin. We also evaluate the differential conductance and find the unitary limit peak 2{{e}2}/h at zero voltage as well as peaks at voltages corresponding to the resonances. We propose that detection of the resonances and related peaks in the differential conductance provide as strong support for the presence of an MBS.
Chern and Majorana modes of quasiperiodic systems
NASA Astrophysics Data System (ADS)
Naumis, Gerardo; Satija, Indubala
2014-03-01
In this work, we investigate the self-similar states found in quasiperiodic systems characterized by topological invariants-the Chern numbers. We show that the topology introduces a competing length in the self-similar band edge states transforming peaks into doublets of size equal to the Chern number. This length intertwines with quasiperiodicity and introduces an intrinsic scale, producing Chern beats related to Friedel oscillations. An explanation based on Thouless equations for band edge modes of the Harper equation is provided to understand the Chern dressing of the fractal spectrum. Chern numbers also influence the zero-energy mode that, for quasiperiodic systems, is related to the Majorana modes: the remnant of the edge localized topological state that delocalizes at the onset to a topological transition. In superconducting wires, the exponentially decaying profile of the edge localized Majorana modes also encode fingerprints of the Chern states that reside in close proximity to zero energy. Apdo. Postal 20-364, 01000, Mexico D.F., Mexico.
Background Model for the Majorana Demonstrator
Cuesta, C.; Abgrall, N.; Aguayo, Estanislao; Avignone, Frank T.; Barabash, Alexander S.; Bertrand, F.; Boswell, M.; Brudanin, V.; Busch, Matthew; Byram, D.; Caldwell, A. S.; Chan, Yuen-Dat; Christofferson, Cabot-Ann; Combs, Dustin C.; Detwiler, Jason A.; Doe, Peter J.; Efremenko, Yuri; Egorov, Viatcheslav; Ejiri, H.; Elliott, S. R.; Fast, James E.; Finnerty, P.; Fraenkle, Florian; Galindo-Uribarri, A.; Giovanetti, G. K.; Goett, J.; Green, M. P.; Gruszko, J.; Guiseppe, Vincente; Gusev, K.; Hallin, A. L.; Hazama, R.; Hegai, A.; Henning, Reyco; Hoppe, Eric W.; Howard, Stanley; Howe, M. A.; Keeter, K.; Kidd, M. F.; Kochetov, Oleg; Konovalov, S.; Kouzes, Richard T.; Laferriere, Brian D.; Leon, Jonathan D.; Leviner, L.; Loach, J. C.; MacMullin, J.; MacMullin, S.; Martin, R. D.; Meijer, S. J.; Mertens, S.; Nomachi, Masaharu; Orrell, John L.; O'Shaughnessy, C.; Overman, Nicole R.; Phillips, D.; Poon, Alan; Pushkin, K.; Radford, D. C.; Rager, J.; Rielage, Keith; Robertson, R. G. H.; Romero-Romero, E.; Ronquest, M. C.; Schubert, Alexis G.; Shanks, B.; Shima, T.; Shirchenko, M.; Snavely, Kyle J.; Snyder, N.; Suriano, Anne-Marie; Thompson, J.; Timkin, V.; Tornow, Werner; Trimble, J. E.; Varner, R. L.; Vasilyev, Sergey; Vetter, Kai; Vorren, Kris R.; White, Brandon R.; Wilkerson, J. F.; Wiseman, C.; Xu, W.; Yakushev, E.; Young, A.; Yu, Chang-Hong; Yumatov, Vladimir
2015-06-01
The Majorana Collaboration is constructing a prototype system containing 40 kg of HPGe detectors to demonstrate the feasibility and potential of a future tonne-scale experiment to search for neutrinoless double-beta (0v BB) decay in 76Ge. In view of the requirement that the next generation of tonne-scale Ge-based 0vBB-decay experiment be capable of probing the neutrino mass scale in the inverted-hierarchy region, a major goal of theMajorana Demonstrator is to demonstrate a path forward to achieving a background rate at or below 1 cnt/(ROI-t-y) in the 4 keV region of interest around the Q-value at 2039 keV. This goal is pursued through a combination of a significant reduction of radioactive impurities in construction materials with analytical methods for background rejection, for example using powerful pulse shape analysis techniques profiting from the p-type point contact HPGe detectors technology. The effectiveness of these methods is assessed using Geant4 simulations of the different background components whose purity levels are constrained from radioassay measurements.
Search for Majorana fermions in topological superconductors.
Pan, Wei; Shi, Xiaoyan; Hawkins, Samuel D.; Klem, John Frederick
2014-10-01
The goal of this project is to search for Majorana fermions (a new quantum particle) in a topological superconductor (a new quantum matter achieved in a topological insulator proximitized by an s-wave superconductor). Majorana fermions (MFs) are electron-like particles that are their own anti-particles. MFs are shown to obey non-Abelian statistics and, thus, can be harnessed to make a fault-resistant topological quantum computer. With the arrival of topological insulators, novel schemes to create MFs have been proposed in hybrid systems by combining a topological insulator with a conventional superconductor. In this LDRD project, we will follow the theoretical proposals to search for MFs in one-dimensional (1D) topological superconductors. 1D topological superconductor will be created inside of a quantum point contact (with the metal pinch-off gates made of conventional s-wave superconductors such as niobium) in a two-dimensional topological insulator (such as inverted type-II InAs/GaSb heterostructure).
Majorana bound states in magnetic skyrmions (Conference Presentation)
NASA Astrophysics Data System (ADS)
Stano, Peter
2016-10-01
Magnetic skyrmions are highly mobile nanoscale topological spin textures. We show, both analytically and numerically, that a magnetic skyrmion of an even azimuthal winding number placed in proximity to an s-wave superconductor hosts a zero-energy Majorana bound state in its core, when the exchange coupling between the itinerant electrons and the skyrmion is strong. This Majorana bound state is stabilized by the presence of a spin-orbit interaction. We propose the use of a superconducting tri-junction to realize non-Abelian statistics of such Majorana bound states. http://arxiv.org/abs/1602.00968
Nonlinear Landau-Zener tunneling in Majorana's stellar representation
NASA Astrophysics Data System (ADS)
Guo, Qiuyi; Liu, Haodi; Zhou, Tianji; Chen, Xu-Zong; Wu, Biao
2016-06-01
By representing the evolution of a quantum state with the trajectories of the stars on a Bloch sphere, the Majorana's stellar representation provides an intuitive way to understand quantum motion in a high dimensional projective Hilbert space. In this work we show that the Majorana's representation offers a very interesting and intuitive way to understand the nonlinear Landau-Zener tunneling. In particular, the breakdown of adiabaticity in this tunneling phenomenon can be understood as some of the stars never reaching the south pole. We also establish a connection between the Majorana stars in the second quantized model and the single star in the mean field model by using the reduced density matrix.
Majoranas with and without a ‘character’: hybridization, braiding and chiral Majorana number
NASA Astrophysics Data System (ADS)
Sedlmayr, N.; Guigou, M.; Simon, P.; Bena, C.
2015-11-01
In this paper we demonstrate under what conditions a pseudo-spin degree of freedom or character can be ascribed to Majorana bound states (MBS). These exotic states can be created at the boundaries of non-interacting systems, corresponding to D, DIII and BDI in the usual classification scheme, and we focus on one dimension. We have found that such a character is directly related to the class of the topological superconductor and its description by a {Z} , rather than a {{{Z}}2} , invariant which corresponds to the BDI class. We have also found that the DIII case with mirror symmetry, which supports multiple MBS, is in fact equivalent to the BDI class with an additional time-reversal symmetry. In all cases where a character can be given to the Majorana states we show how to construct the appropriate local operator explicitly with various examples. We also examine the consequences of the Majorana character by considering possible hybridization of MBS brought into proximity and find that two MBS with the same character do not hybridize. Finally, we show that having this character or not has no consequence on the braiding properties of MBS.
Correlations between Majorana Fermions Through a Superconductor
NASA Astrophysics Data System (ADS)
Zyuzin, A. A.; Rainis, Diego; Klinovaja, Jelena; Loss, Daniel
2013-08-01
We consider a model of ballistic quasi-one-dimensional semiconducting wire with intrinsic spin-orbit interaction placed on the surface of a bulk s-wave superconductor (SC), in the presence of an external magnetic field. This setup has been shown to give rise to a topological superconducting state in the wire, characterized by a pair of Majorana-fermion (MF) bound states formed at the two ends of the wire. Here, we demonstrate that besides the well-known direct-overlap-induced energy splitting, the two MF bound states may hybridize via elastic tunneling processes through virtual quasiparticle states in the SC, giving rise to an additional energy splitting between MF states from the same as well as from different wires.
Majorana physics through the Cabibbo Haze
NASA Astrophysics Data System (ADS)
Kile, Jennifer; Pérez, M. Jay; Ramond, Pierre; Zhang, Jue
2014-02-01
We present a model in which the Supersymmetric Standard Model is aug-mented by the family symmetry . Motivated by SO(10), where the charge two-thirds and neutral Dirac Yukawa matrices are related, we propose, using family symmetry, a special form for the seesaw Majorana matrix; it contains a squared correlated hierarchy, allowing it to mitigate the severe hierarchy of the quark sector. It is reproduced naturally by the invariant operators of , with the hierarchy carried by familon fields. In addition to relating the hierarchy of the Δ I w = 1 /2 to the Δ I w = 0 sector, it contains a Gatto-Sartori-Tonin like relation, predicts a normal hierarchy for Tri-bimaximal and Golden Ratio mixings, and gives specific values for the light neutrino masses.
Majorana Physics Through the Cabibbo Haze
NASA Astrophysics Data System (ADS)
Kile, Jennifer; Perez, Michael; Ramond, Pierre; Zhang, Jue
2014-03-01
We present a model in which the Supersymmetric Standard Model is augmented by the family symmetry Z7Z3 . Motivated by SO (10) , where the charge two-thirds and neutral Dirac Yukawa matrices are related, we propose, using family symmetry, a special form for the seesaw Majorana matrix; it contains a squared correlated hierarchy, allowing it to mitigate the severe hierarchy of the quark sector. It is reproduced naturally by the invariant operators of Z7Z3 , with the hierarchy carried by familon fields. In addition to relating the hierarchy of the ΔIw = 1 / 2 to the ΔIw = 0 sector, it contains a Gatto-Sartori-Tonin like relation, predicts a normal hierarchy for Tri-bimaximal and Golden Ratio mixings, and gives specific values for the light neutrino masses.
Role of dissipation in realistic Majorana nanowires
NASA Astrophysics Data System (ADS)
Liu, Chun-Xiao; Sau, Jay D.; Das Sarma, S.
2017-02-01
We carry out a realistic simulation of Majorana nanowires in order to understand the latest high-quality experimental data [H. Zhang et al., arXiv:1603.04069 (2016)] and, in the process, develop a comprehensive picture for what physical mechanisms may be operational in realistic nanowires leading to discrepancies between minimal theory and experimental observations (e.g., weakness and broadening of the zero-bias peak and breaking of particle-hole symmetry). Our focus is on understanding specific intriguing features in the data, and our goal is to establish matters of principle controlling the physics of the best possible nanowires available in current experiments. We identify dissipation, finite temperature, multi-sub-band effects, and the finite tunnel barrier as the four most important physical mechanisms controlling the zero-bias conductance peak. Our theoretical results including these realistic effects agree well with the best available experimental data in ballistic nanowires.
New scheme for braiding Majorana fermions
Wu, Long-Hua; Liang, Qi-Feng; Hu, Xiao
2014-01-01
Non-Abelian statistics can be achieved by exchanging two vortices in topological superconductors with each grabbing a Majorana fermion (MF) as zero-energy quasi-particle at the cores. However, in experiments it is difficult to manipulate vortices. In the present work, we propose a way to braid MFs without moving vortices. The only operation required in the present scheme is to turn on and off local gate voltages, which liberates a MF from its original host vortex and transports it along the prepared track. We solve the time-dependent Bogoliubov–de Gennes equation numerically, and confirm that the MFs are protected provided the switching of gate voltages for exchanging MFs are adiabatic, which takes only several nano seconds given reasonable material parameters. By monitoring the time evolution of MF wave-functions, we show that non-Abelian statistics is achieved. PMID:27877725
Current correlations in a Majorana beam splitter
NASA Astrophysics Data System (ADS)
Haim, Arbel; Berg, Erez; von Oppen, Felix; Oreg, Yuval
2015-12-01
We study current correlations in a T junction composed of a grounded topological superconductor and of two normal-metal leads which are biased at a voltage V . We show that the existence of an isolated Majorana zero mode in the junction dictates a universal behavior for the cross correlation of the currents through the two normal-metal leads of the junction. The cross correlation is negative and approaches zero at high bias voltages as -1 /V . This behavior is robust in the presence of disorder and multiple transverse channels, and persists at finite temperatures. In contrast, an accidental low-energy Andreev bound state gives rise to nonuniversal behavior of the cross correlation. We employ numerical transport simulations to corroborate our conclusions.
Odd-frequency pairing of interacting Majorana fermions
Huang, Zhoushen; Wolfle, P.; Balatsky, Alexander V.
2015-09-14
In this study, Majorana fermions are rising as a promising key component in quantum computation. Although the prevalent approach is to use a quadratic (i.e., noninteracting) Majorana Hamiltonian, when expressed in terms of Dirac fermions, generically the Hamiltonian involves interaction terms. Here we focus on the possible pair correlations in a simple model system. We study a model of Majorana fermions coupled to a boson mode and show that the anomalous correlator between different Majorana fermions, located at opposite ends of a topological wire, exhibits odd-frequency behavior. It is stabilized when the coupling strength g is above a critical valuemore » gc. We use both, conventional diagrammatic theory and a functional integral approach, to derive the gap equation, the critical temperature, the gap function, the critical coupling, and a Ginzburg-Landau theory that allows discussing a possible subleading admixture of even-frequency pairing.« less
Electron teleportation via Majorana bound states in a mesoscopic superconductor.
Fu, Liang
2010-02-05
Zero-energy Majorana bound states in superconductors have been proposed to be potential building blocks of a topological quantum computer, because quantum information can be encoded nonlocally in the fermion occupation of a pair of spatially separated Majorana bound states. However, despite intensive efforts, nonlocal signatures of Majorana bound states have not been found in charge transport. In this work, we predict a striking nonlocal phase-coherent electron transfer process by virtue of tunneling in and out of a pair of Majorana bound states. This teleportation phenomenon only exists in a mesoscopic superconductor because of an all-important but previously overlooked charging energy. We propose an experimental setup to detect this phenomenon in a superconductor-quantum-spin-Hall-insulator-magnetic-insulator hybrid system.
Odd-frequency pairing of interacting Majorana fermions
NASA Astrophysics Data System (ADS)
Huang, Zhoushen; Wölfle, P.; Balatsky, A. V.
2015-09-01
Majorana fermions are rising as a promising key component in quantum computation. Although the prevalent approach is to use a quadratic (i.e., noninteracting) Majorana Hamiltonian, when expressed in terms of Dirac fermions, generically the Hamiltonian involves interaction terms. Here we focus on the possible pair correlations in a simple model system. We study a model of Majorana fermions coupled to a boson mode and show that the anomalous correlator between different Majorana fermions, located at opposite ends of a topological wire, exhibits odd-frequency behavior. It is stabilized when the coupling strength g is above a critical value gc. We use both, conventional diagrammatic theory and a functional integral approach, to derive the gap equation, the critical temperature, the gap function, the critical coupling, and a Ginzburg-Landau theory that allows discussing a possible subleading admixture of even-frequency pairing.
Odd-frequency pairing of interacting Majorana fermions
Huang, Zhoushen; Wolfle, P.; Balatsky, Alexander V.
2015-09-14
In this study, Majorana fermions are rising as a promising key component in quantum computation. Although the prevalent approach is to use a quadratic (i.e., noninteracting) Majorana Hamiltonian, when expressed in terms of Dirac fermions, generically the Hamiltonian involves interaction terms. Here we focus on the possible pair correlations in a simple model system. We study a model of Majorana fermions coupled to a boson mode and show that the anomalous correlator between different Majorana fermions, located at opposite ends of a topological wire, exhibits odd-frequency behavior. It is stabilized when the coupling strength g is above a critical value g_{c}. We use both, conventional diagrammatic theory and a functional integral approach, to derive the gap equation, the critical temperature, the gap function, the critical coupling, and a Ginzburg-Landau theory that allows discussing a possible subleading admixture of even-frequency pairing.
Majorana dc Josephson current mediated by a quantum dot.
Xu, Luting; Li, Xin-Qi; Sun, Qing-Feng
2017-05-17
The Josephson supercurrent through a hybrid Majorana-quantum dot-Majorana junction is investigated. We particularly analyze the effect of spin-selective coupling between the Majorana and quantum dot states, which only emerges in the topological phase and will influence the current through bent junctions and/or in the presence of magnetic fields in the quantum dot. We find that the characteristic behavior of the supercurrent through this system is quite counterintuitive, differing remarkably from the resonant tunneling, e.g. through the similar (normal phase) superconductor-quantum dot-superconductor junction. Our analysis is carried out under the influence of the full set-up parameters and for both the [Formula: see text] and [Formula: see text] periodic currents. The present study is expected to be relevant to the future exploration of applications of Majorana-nanowire circuits.
Robust Majorana Conductance Peaks for a Superconducting Lead
NASA Astrophysics Data System (ADS)
Peng, Yang; Pientka, Falko; Vinkler-Aviv, Yuval; Glazman, Leonid I.; von Oppen, Felix
2015-12-01
Experimental evidence for Majorana bound states largely relies on measurements of the tunneling conductance. While the conductance into a Majorana state is in principle quantized to 2 e2/h , observation of this quantization has been elusive, presumably due to temperature broadening in the normal-metal lead. Here, we propose to use a superconducting lead instead, whose gap strongly suppresses thermal excitations. For a wide range of tunneling strengths and temperatures, a Majorana state is then signaled by symmetric conductance peaks at e V =±Δ of a universal height G =(4 -π )2 e2/h . For a superconducting scanning tunneling microscope tip, Majorana states appear as spatial conductance plateaus while the conductance varies with the local wave function for trivial Andreev bound states. We discuss effects of nonresonant (bulk) Andreev reflections and quasiparticle poisoning.
All Majorana Models with Translation Symmetry are Supersymmetric
NASA Astrophysics Data System (ADS)
Hsieh, Timothy H.; Halász, Gábor B.; Grover, Tarun
2016-10-01
We establish results similar to Kramers and Lieb-Schultz-Mattis theorems but involving only translation symmetry and for Majorana modes. In particular, we show that all states are at least doubly degenerate in any one- and two-dimensional array of Majorana modes with translation symmetry, periodic boundary conditions, and an odd number of modes per unit cell. Moreover, we show that all such systems have an underlying N =2 supersymmetry and explicitly construct the generator of the supersymmetry. Furthermore, we establish that there cannot be a unique gapped ground state in such one-dimensional systems with antiperiodic boundary conditions. These general results are fundamentally a consequence of the fact that translations for Majorana modes are represented projectively, which in turn stems from the anomalous nature of a single Majorana mode. An experimental signature of the degeneracy arising from supersymmetry is a zero-bias peak in tunneling conductance.
Fault tolerant quantum random number generator certified by Majorana fermions
NASA Astrophysics Data System (ADS)
Deng, Dong-Ling; Duan, Lu-Ming
2013-03-01
Braiding of Majorana fermions gives accurate topological quantum operations that are intrinsically robust to noise and imperfection, providing a natural method to realize fault-tolerant quantum information processing. Unfortunately, it is known that braiding of Majorana fermions is not sufficient for implementation of universal quantum computation. Here we show that topological manipulation of Majorana fermions provides the full set of operations required to generate random numbers by way of quantum mechanics and to certify its genuine randomness through violation of a multipartite Bell inequality. The result opens a new perspective to apply Majorana fermions for robust generation of certified random numbers, which has important applications in cryptography and other related areas. This work was supported by the NBRPC (973 Program) 2011CBA00300 (2011CBA00302), the IARPA MUSIQC program, the ARO and the AFOSR MURI program.
The Majorana Neutrinoless Double-Beta Decay Program
NASA Astrophysics Data System (ADS)
Guiseppe, Vincente
2014-09-01
Neutrinoless double-beta decay searches play a major role in determining the nature of neutrinos, the existence of a lepton violating process, and the effective Majorana neutrino mass. The Majorana Collaboration is assembling an array of high purity Ge detectors to search for neutrinoless double-beta decay in 76Ge. The Majorana Demonstrator, containing 40 kg (30 kg enriched in 76Ge) of Ge detectors, is currently being constructed and commissioned at the Sanford Underground Research Facility in Lead, South Dakota. The initial goals are to demonstrate the required background and scalability of a Ge-based, tonne-scale experiment. The status and potential physics reach of the Majorana Demonstrator experiment will be presented. Neutrinoless double-beta decay searches play a major role in determining the nature of neutrinos, the existence of a lepton violating process, and the effective Majorana neutrino mass. The Majorana Collaboration is assembling an array of high purity Ge detectors to search for neutrinoless double-beta decay in 76Ge. The Majorana Demonstrator, containing 40 kg (30 kg enriched in 76Ge) of Ge detectors, is currently being constructed and commissioned at the Sanford Underground Research Facility in Lead, South Dakota. The initial goals are to demonstrate the required background and scalability of a Ge-based, tonne-scale experiment. The status and potential physics reach of the Majorana Demonstrator experiment will be presented. We acknowledge support from the Office of Nuclear Physics in the DOE Office of Science, the Particle and Nuclear Astrophysics Program of the National Science Foundation and the Russian Foundation for Basic Research.
Rephasing-invariant CP violating parameters with Majorana neutrinos
NASA Astrophysics Data System (ADS)
Nieves, José F.; Pal, Palash B.
2001-10-01
We analyze the dependence of the squared amplitudes on the rephasing-invariant CP-violating parameters of the lepton sector, involving Majorana neutrinos, for various lepton-conserving and lepton-violating processes. We analyze the conditions under which the CP-violating effects in such processes vanish, in terms of the minimal set of rephasing invariants, giving special attention to the dependence on the extra CP-violating parameters that are due to the Majorana nature of the neutrinos.
Arbitrary dimensional Majorana dualities and architectures for topological matter
NASA Astrophysics Data System (ADS)
Nussinov, Zohar; Ortiz, Gerardo; Cobanera, Emilio
2012-08-01
Motivated by the prospect of attaining Majorana modes at the ends of nanowires, we analyze interacting Majorana systems on general networks and lattices in an arbitrary number of dimensions, and derive universal spin duals. We prove that these interacting Majorana systems, quantum Ising gauge theories, and transverse-field Ising models with annealed bimodal disorder are all dual to one another on general planar graphs. This leads to an interesting connection between heavily disordered annealed Ising systems and uniform Ising theories with nearest-neighbor interactions. As any Dirac fermion (including electronic) operator can be expressed as a linear combination of two Majorana fermion operators, our results further lead to dualities between interacting Dirac fermionic systems on rather general lattices and graphs and corresponding spin systems. Such general complex Majorana architectures (other than those of simple square or other crystalline arrangements) might be of empirical relevance. As these systems display low-dimensional symmetries, they are candidates for realizing topological quantum order. The spin duals allow us to predict the feasibility of various standard transitions as well as spin-glass-type behavior in interacting Majorana fermion or electronic systems. Several systems that can be simulated by arrays of Majorana wires are further introduced and investigated: (1) the XXZ honeycomb compass model (intermediate between the classical Ising model on the honeycomb lattice and Kitaev's honeycomb model), (2) a checkerboard lattice realization of the model of Xu and Moore for superconducting (p+ip) arrays, and a (3) compass-type two-flavor Hubbard model with both pairing and hopping terms. By the use of our dualities (tantamount to high-dimensional fermionization), we show that all of these systems lie in the three-dimensional Ising universality class. We further discuss how the existence of topological orders and bounds on autocorrelation times can be
Majorana Fermions in Disordered Quasi-One-Dimensional Topological Superconductors
NASA Astrophysics Data System (ADS)
Potter, Andrew; Lee, Patrick
2012-02-01
Majorana fermions have long been predicted to emerge in certain quantum Hall states and other naturally occurring p-wave superconductors. However, these materials are quite delicate and consequently the experimental realization of Majorana fermions remains elusive. The possibility of engineering 1D networks of topological superconducting wires from conventional materials offers a promising alternative route to realize Majorana fermions and probe their predicted non-Abelian statistics. In practice, it is impossible to fabricate perfectly clean and strictly one-dimensional structures; how do these non-idealities affect the proposed Majorana states? This talk will show that Majorana end states are robust away from the strict 1D limit, so long as the sample width is not much larger than the superconducting coherence length. The effects of disorder are potentially more severe, as impurity scattering is generally pair-breaking and tends to suppress the gap protecting the Majorana modes. Finally, we propose new candidate materials and geometries that greatly simplify the experimental setup and mitigate the harmful effects of disorder.
Majorana fermion exchange in quasi-one-dimensional networks
NASA Astrophysics Data System (ADS)
Clarke, David J.; Sau, Jay D.; Tewari, Sumanta
2011-07-01
Heterostructures of spin-orbit coupled materials with s-wave superconductors are thought to be capable of supporting zero-energy Majorana bound states. Such excitations are known to obey non-Abelian statistics in two dimensions, and are thus relevant to topological quantum computation (TQC). In a one-dimensional system, Majorana states are localized to phase boundaries. In order to bypass the constraints of one dimension, a wire network may be created, allowing the exchange of Majoranas by way of junctions in the network. Alicea have proposed such a network as a platform for TQC, showing that the Majorana bound states obey non-Abelian exchange statistics even in quasi-one-dimensional systems. Here we show that the particular realization of non-Abelian statistics produced in a Majorana wire network is highly dependent on the local properties of individual wire junctions. For a simply connected network, the possible realizations can be characterized by the chirality of individual junctions. There is in general no requirement for junction chiralities to remain consistent across a wire network. We show how the chiralities of different junctions may be compared experimentally and discuss the implications for TQC in Majorana wire networks.
NASA Astrophysics Data System (ADS)
Samanta, Rome; Chakraborty, Mainak; Ghosal, Ambar
2016-03-01
We evaluate the Majorana phases for a general 3 × 3 complex symmetric neutrino mass matrix on the basis of Mohapatra-Rodejohann's phase convention using the three rephasing invariant quantities I12, I13 and I23 proposed by Sarkar and Singh. We find them interesting as they allow us to evaluate each Majorana phase in a model independent way even if one eigenvalue is zero. Utilizing the solution of a general complex symmetric mass matrix for eigenvalues and mixing angles we determine the Majorana phases for both the hierarchies, normal and inverted, taking into account the constraints from neutrino oscillation global fit data as well as bound on the sum of the three light neutrino masses (Σimi) and the neutrinoless double beta decay (ββ0ν) parameter |m11 |. This methodology of finding the Majorana phases is applied thereafter in some predictive models for both the hierarchical cases (normal and inverted) to evaluate the corresponding Majorana phases and it is shown that all the sub cases presented in inverted hierarchy section can be realized in a model with texture zeros and scaling ansatz within the framework of inverse seesaw although one of the sub cases following the normal hierarchy is yet to be established. Except the case of quasi degenerate neutrinos, the methodology obtained in this work is able to evaluate the corresponding Majorana phases, given any model of neutrino masses.
Exponential protection of zero modes in Majorana islands
NASA Astrophysics Data System (ADS)
Albrecht, S. M.; Higginbotham, A. P.; Madsen, M.; Kuemmeth, F.; Jespersen, T. S.; Nygård, J.; Krogstrup, P.; Marcus, C. M.
2016-03-01
Majorana zero modes are quasiparticle excitations in condensed matter systems that have been proposed as building blocks of fault-tolerant quantum computers. They are expected to exhibit non-Abelian particle statistics, in contrast to the usual statistics of fermions and bosons, enabling quantum operations to be performed by braiding isolated modes around one another. Quantum braiding operations are topologically protected insofar as these modes are pinned near zero energy, with the departure from zero expected to be exponentially small as the modes become spatially separated. Following theoretical proposals, several experiments have identified signatures of Majorana modes in nanowires with proximity-induced superconductivity and atomic chains, with small amounts of mode splitting potentially explained by hybridization of Majorana modes. Here, we use Coulomb-blockade spectroscopy in an InAs nanowire segment with epitaxial aluminium, which forms a proximity-induced superconducting Coulomb island (a ‘Majorana island’) that is isolated from normal-metal leads by tunnel barriers, to measure the splitting of near-zero-energy Majorana modes. We observe exponential suppression of energy splitting with increasing wire length. For short devices of a few hundred nanometres, sub-gap state energies oscillate as the magnetic field is varied, as is expected for hybridized Majorana modes. Splitting decreases by a factor of about ten for each half a micrometre of increased wire length. For devices longer than about one micrometre, transport in strong magnetic fields occurs through a zero-energy state that is energetically isolated from a continuum, yielding uniformly spaced Coulomb-blockade conductance peaks, consistent with teleportation via Majorana modes. Our results help to explain the trivial-to-topological transition in finite systems and to quantify the scaling of topological protection with end-mode separation.
Exponential protection of zero modes in Majorana islands.
Albrecht, S M; Higginbotham, A P; Madsen, M; Kuemmeth, F; Jespersen, T S; Nygård, J; Krogstrup, P; Marcus, C M
2016-03-10
Majorana zero modes are quasiparticle excitations in condensed matter systems that have been proposed as building blocks of fault-tolerant quantum computers. They are expected to exhibit non-Abelian particle statistics, in contrast to the usual statistics of fermions and bosons, enabling quantum operations to be performed by braiding isolated modes around one another. Quantum braiding operations are topologically protected insofar as these modes are pinned near zero energy, with the departure from zero expected to be exponentially small as the modes become spatially separated. Following theoretical proposals, several experiments have identified signatures of Majorana modes in nanowires with proximity-induced superconductivity and atomic chains, with small amounts of mode splitting potentially explained by hybridization of Majorana modes. Here, we use Coulomb-blockade spectroscopy in an InAs nanowire segment with epitaxial aluminium, which forms a proximity-induced superconducting Coulomb island (a 'Majorana island') that is isolated from normal-metal leads by tunnel barriers, to measure the splitting of near-zero-energy Majorana modes. We observe exponential suppression of energy splitting with increasing wire length. For short devices of a few hundred nanometres, sub-gap state energies oscillate as the magnetic field is varied, as is expected for hybridized Majorana modes. Splitting decreases by a factor of about ten for each half a micrometre of increased wire length. For devices longer than about one micrometre, transport in strong magnetic fields occurs through a zero-energy state that is energetically isolated from a continuum, yielding uniformly spaced Coulomb-blockade conductance peaks, consistent with teleportation via Majorana modes. Our results help to explain the trivial-to-topological transition in finite systems and to quantify the scaling of topological protection with end-mode separation.
Dynamical Majorana edge modes in a broad class of topological mechanical systems
NASA Astrophysics Data System (ADS)
Prodan, Emil; Dobiszewski, Kyle; Kanwal, Alokik; Palmieri, John; Prodan, Camelia
2017-02-01
Mechanical systems can display topological characteristics similar to that of topological insulators. Here we report a large class of topological mechanical systems related to the BDI symmetry class. These are self-assembled chains of rigid bodies with an inversion centre and no reflection planes. The particle-hole symmetry characteristic to the BDI symmetry class stems from the distinct behaviour of the translational and rotational degrees of freedom under inversion. This and other generic properties led us to the remarkable conclusion that, by adjusting the gyration radius of the bodies, one can always simultaneously open a gap in the phonon spectrum, lock-in all the characteristic symmetries and generate a non-trivial topological invariant. The particle-hole symmetry occurs around a finite frequency, and hence we can witness a dynamical topological Majorana edge mode. Contrasting a floppy mode occurring at zero frequency, a dynamical edge mode can absorb and store mechanical energy, potentially opening new applications of topological mechanics.
Experimental monitoring for the MAJORANA DEMONSTRATOR
NASA Astrophysics Data System (ADS)
Xu, Wenqin; MAJORANA Collaboration
2017-01-01
The MAJORANA DEMONSTRATOR neutrinoless double beta (0 νββ) decay experiment has instrumented two modules of high purity germanium (HPGe) detectors to search for 0 νββ decay in 76Ge. The experiment has started accumulating quality data towards its goal of demonstrating the technical feasibility and low backgrounds for a next generation Ge-based 0 νββ experiment. It is critical to extensively monitor the performance of the experimental apparatus without disturbing the blindness data-taking scheme. The experimental monitoring is composed of several stages including, for example, the live monitoring embedded in the Data-Acquisition system, onsite near-live monitoring and data production monitoring. In all stages, automatic alerting mechanisms and scheduled manual checks are implemented in a coordinated way. In this talk, we will discuss the internal management of each experimental monitoring stage and their relationships to each other. This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics, the Particle Astrophysics and Nuclear Physics Programs of the National Science Foundation, and Sanford Underground Research Facility.
Viewing Majorana Bound States by Rabi Oscillations
NASA Astrophysics Data System (ADS)
Wang, Zhi; Liang, Qi-Feng; Yao, Dao-Xin; Hu, Xiao
2015-07-01
We propose to use Rabi oscillation as a probe to view the fractional Josepshon relation (FJR) associated with Majorana bound states (MBSs) expected in one-dimensional topological superconductors. The system consists of a quantum dot (QD) and an rf-SQUID with MBSs at the Josephson junction. Rabi oscillations between energy levels formed by MBSs are induced by ac gate voltage controlling the coupling between QD and MBS when the photon energy proportional to the ac frequency matches gap between quantum levels formed by MBSs and QD. As a manifestation of the Rabi oscillation in the whole system involving MBSs, the electron occupation on QD oscillates with time, which can be measured by charge sensing techniques. With Floquet theorem and numerical analysis we reveal that from the resonant driving frequency for coherent Rabi oscillation one can directly map out the FJR cos(πΦ/Φ0) as a signature of MBSs, with Φ the magnetic flux through SQUID and Φ0 = hc/2e the flux quantum. The present scheme is expected to provide a clear evidence for MBSs under intensive searching.
Majorana fermions in condensed-matter physics
NASA Astrophysics Data System (ADS)
Leggett, A. J.
2016-06-01
It is an honor and a pleasure to have been invited to give a talk in this conference celebrating the memory of the late Professor Abdus Salam. To my regret, I did not know Professor Salam personally, but I am very aware of his work and of his impact on my area of specialization, condensed matter physics, both intellectually through his ideas on spontaneously broken symmetry and more practically through his foundation of the ICTP. Since I assume that most of this audience are not specialized in condensed-matter physics, I thought I would talk about one topic which to some extent bridges this field and the particle-physics interests of Salam, namely Majorana fermions (M.F.s). However, as we shall see, the parallels which are often drawn in the current literature may be a bit too simplistic. I will devote most of this talk to a stripped-down exposition of the current orthodoxy concerning M.F.s. in condensed-matter physics and their possible applications to topological quantum computing (TQC), and then at the end briefly indicate why I believe this orthodoxy may be seriously misleading.
Quasiclassical theory of disordered multi-channel Majorana quantum wires
NASA Astrophysics Data System (ADS)
Neven, Patrick; Bagrets, Dmitry; Altland, Alexander
2013-05-01
Multi-channel spin-orbit quantum wires, when subjected to a magnetic field and proximity coupled to an s-wave superconductor, may support Majorana states. We study what happens to these systems in the presence of disorder. Inspired by the widely established theoretical methods of mesoscopic superconductivity, we develop á la Eilenberger a quasiclassical approach to topological nanowires valid in the limit of strong spin-orbit coupling. We find that the ‘Majorana number’ {\\cal M} , distinguishing between the state with Majorana fermions (symmetry class B) and no Majorana fermions (class D), is given by the product of two Pfaffians of gapped quasiclassical Green's functions fixed by the right and left terminals connected to the wire. A numerical solution of the Eilenberger equations reveals that the class D disordered quantum wires are prone to the formation of the zero-energy anomaly (class D impurity spectral peak) in the local density of states that shares the key features of the Majorana peak. In this way, we confirm the robustness of our previous conclusions (Bagrets and Altland 2012 Phys. Rev. Lett. 109 227005) on a more restrictive system setup. Generally speaking, we find that the quasiclassical approach provides a highly efficient means to address disordered class D superconductors both in the presence and in the absence of topological structures.
A note on the path integral representation for Majorana fermions
NASA Astrophysics Data System (ADS)
Greco, Andrés
2016-04-01
Majorana fermions are currently of huge interest in the context of nanoscience and condensed matter physics. Different to usual fermions, Majorana fermions have the property that the particle is its own anti-particle thus, they must be described by real fields. Mathematically, this property makes nontrivial the quantization of the problem due, for instance, to the absence of a Wick-like theorem. In view of the present interest on the subject, it is important to develop different theoretical approaches in order to study problems where Majorana fermions are involved. In this note we show that Majorana fermions can be studied in the context of field theories for constrained systems. Using the Faddeev-Jackiw formalism for quantum field theories with constraints, we derived the path integral representation for Majorana fermions. In order to show the validity of the path integral we apply it to an exactly solvable problem. This application also shows that it is rather simple to perform systematic calculations on the basis of the present framework.
NASA Astrophysics Data System (ADS)
Chatrchyan, S.; Khachatryan, V.; Sirunyan, A. M.; Tumasyan, A.; Adam, W.; Aguilo, E.; Bergauer, T.; Dragicevic, M.; Erö, J.; Fabjan, C.; Friedl, M.; Frühwirth, R.; Ghete, V. M.; Hammer, J.; Hörmann, N.; Hrubec, J.; Jeitler, M.; Kiesenhofer, W.; Knünz, V.; Krammer, M.; Krätschmer, I.; Liko, D.; Mikulec, I.; Pernicka, M.; Rahbaran, B.; Rohringer, C.; Rohringer, H.; Schöfbeck, R.; Strauss, J.; Taurok, A.; Waltenberger, W.; Walzel, G.; Widl, E.; Wulz, C.-E.; Mossolov, V.; Shumeiko, N.; Suarez Gonzalez, J.; Bansal, M.; Bansal, S.; Cornelis, T.; De Wolf, E. A.; Janssen, X.; Luyckx, S.; Mucibello, L.; Ochesanu, S.; Roland, B.; Rougny, R.; Selvaggi, M.; Staykova, Z.; Van Haevermaet, H.; Van Mechelen, P.; Van Remortel, N.; Van Spilbeeck, A.; Blekman, F.; Blyweert, S.; D'Hondt, J.; Gonzalez Suarez, R.; Kalogeropoulos, A.; Maes, M.; Olbrechts, A.; Van Doninck, W.; Van Mulders, P.; Van Onsem, G. P.; Villella, I.; Clerbaux, B.; De Lentdecker, G.; Dero, V.; Gay, A. P. R.; Hreus, T.; Léonard, A.; Marage, P. E.; Reis, T.; Thomas, L.; Vander Marcken, G.; Vander Velde, C.; Vanlaer, P.; Wang, J.; Adler, V.; Beernaert, K.; Cimmino, A.; Costantini, S.; Garcia, G.; Grunewald, M.; Klein, B.; Lellouch, J.; Marinov, A.; Mccartin, J.; Ocampo Rios, A. A.; Ryckbosch, D.; Strobbe, N.; Thyssen, F.; Tytgat, M.; Verwilligen, P.; Walsh, S.; Yazgan, E.; Zaganidis, N.; Basegmez, S.; Bruno, G.; Castello, R.; Ceard, L.; Delaere, C.; du Pree, T.; Favart, D.; Forthomme, L.; Giammanco, A.; Hollar, J.; Lemaitre, V.; Liao, J.; Militaru, O.; Nuttens, C.; Pagano, D.; Pin, A.; Piotrzkowski, K.; Schul, N.; Vizan Garcia, J. M.; Beliy, N.; Caebergs, T.; Daubie, E.; Hammad, G. H.; Alves, G. A.; Correa Martins Junior, M.; De Jesus Damiao, D.; Martins, T.; Pol, M. E.; Souza, M. H. G.; Aldá Júnior, W. L.; Carvalho, W.; Custódio, A.; Da Costa, E. M.; De Oliveira Martins, C.; Fonseca De Souza, S.; Matos Figueiredo, D.; Mundim, L.; Nogima, H.; Oguri, V.; Prado Da Silva, W. L.; Santoro, A.; Soares Jorge, L.; Sznajder, A.; Anjos, T. S.; Bernardes, C. A.; Dias, F. A.; Fernandez Perez Tomei, T. R.; Gregores, E. M.; Lagana, C.; Marinho, F.; Mercadante, P. G.; Novaes, S. F.; Padula, Sandra S.; Genchev, V.; Iaydjiev, P.; Piperov, S.; Rodozov, M.; Stoykova, S.; Sultanov, G.; Tcholakov, V.; Trayanov, R.; Vutova, M.; Dimitrov, A.; Hadjiiska, R.; Kozhuharov, V.; Litov, L.; Pavlov, B.; Petkov, P.; Bian, J. G.; Chen, G. M.; Chen, H. S.; Jiang, C. H.; Liang, D.; Liang, S.; Meng, X.; Tao, J.; Wang, J.; Wang, X.; Wang, Z.; Xiao, H.; Xu, M.; Zang, J.; Zhang, Z.; Asawatangtrakuldee, C.; Ban, Y.; Guo, Y.; Li, W.; Liu, S.; Mao, Y.; Qian, S. J.; Teng, H.; Wang, D.; Zhang, L.; Zou, W.; Avila, C.; Gomez, J. P.; Gomez Moreno, B.; Osorio Oliveros, A. F.; Sanabria, J. C.; Godinovic, N.; Lelas, D.; Plestina, R.; Polic, D.; Puljak, I.; Antunovic, Z.; Kovac, M.; Brigljevic, V.; Duric, S.; Kadija, K.; Luetic, J.; Morovic, S.; Attikis, A.; Galanti, M.; Mavromanolakis, G.; Mousa, J.; Nicolaou, C.; Ptochos, F.; Razis, P. A.; Finger, M.; Finger, M.; Assran, Y.; Elgammal, S.; Ellithi Kamel, A.; Khalil, S.; Mahmoud, M. A.; Radi, A.; Kadastik, M.; Müntel, M.; Raidal, M.; Rebane, L.; Tiko, A.; Eerola, P.; Fedi, G.; Voutilainen, M.; Härkönen, J.; Heikkinen, A.; Karimäki, V.; Kinnunen, R.; Kortelainen, M. J.; Lampén, T.; Lassila-Perini, K.; Lehti, S.; Lindén, T.; Luukka, P.; Mäenpää, T.; Peltola, T.; Tuominen, E.; Tuominiemi, J.; Tuovinen, E.; Ungaro, D.; Wendland, L.; Banzuzi, K.; Karjalainen, A.; Korpela, A.; Tuuva, T.; Besancon, M.; Choudhury, S.; Dejardin, M.; Denegri, D.; Fabbro, B.; Faure, J. L.; Ferri, F.; Ganjour, S.; Givernaud, A.; Gras, P.; Hamel de Monchenault, G.; Jarry, P.; Locci, E.; Malcles, J.; Millischer, L.; Nayak, A.; Rander, J.; Rosowsky, A.; Shreyber, I.; Titov, M.; Baffioni, S.; Beaudette, F.; Benhabib, L.; Bianchini, L.; Bluj, M.; Broutin, C.; Busson, P.; Charlot, C.; Daci, N.; Dahms, T.; Dobrzynski, L.; Granier de Cassagnac, R.; Haguenauer, M.; Miné, P.; Mironov, C.; Naranjo, I. N.; Nguyen, M.; Ochando, C.; Paganini, P.; Sabes, D.; Salerno, R.; Sirois, Y.; Veelken, C.; Zabi, A.; Agram, J.-L.; Andrea, J.; Bloch, D.; Bodin, D.; Brom, J.-M.; Cardaci, M.; Chabert, E. C.; Collard, C.; Conte, E.; Drouhin, F.; Ferro, C.; Fontaine, J.-C.; Gelé, D.; Goerlach, U.; Juillot, P.; Le Bihan, A.-C.; Van Hove, P.; Fassi, F.; Mercier, D.; Beauceron, S.; Beaupere, N.; Bondu, O.; Boudoul, G.; Chasserat, J.; Chierici, R.; Contardo, D.; Depasse, P.; El Mamouni, H.; Fay, J.; Gascon, S.; Gouzevitch, M.; Ille, B.; Kurca, T.; Lethuillier, M.; Mirabito, L.; Perries, S.; Sgandurra, L.; Sordini, V.; Tschudi, Y.; Verdier, P.; Viret, S.; Tsamalaidze, Z.; Anagnostou, G.; Autermann, C.; Beranek, S.; Edelhoff, M.; Feld, L.; Heracleous, N.; Hindrichs, O.; Jussen, R.; Klein, K.
2012-10-01
A search is performed for heavy Majorana neutrinos (N) using an event signature defined by two same-sign charged leptons of the same flavour and two jets. The data correspond to an integrated luminosity of 4.98 fb-1 of pp collisions at a centre-of-mass energy of 7 TeV collected with the CMS detector at the Large Hadron Collider. No excess of events is observed beyond the expected standard model background and therefore upper limits are set on the square of the mixing parameter, |VℓN | 2, for ℓ = e , μ, as a function of heavy Majorana-neutrino mass. These are the first direct upper limits on the heavy Majorana-neutrino mixing for mN > 90 GeV.
6 π Josephson Effect in Majorana Box Devices
NASA Astrophysics Data System (ADS)
Zazunov, A.; Buccheri, F.; Sodano, P.; Egger, R.
2017-02-01
We study Majorana devices featuring a competition between superconductivity and multichannel Kondo physics. Our proposal extends previous work on single-channel Kondo systems to a topologically nontrivial setting of a non-Fermi liquid type, where topological superconductor wires (with gap Δ ) represent leads tunnel coupled to a Coulomb-blockaded Majorana box. On the box, a spin degree of freedom with Kondo temperature TK is nonlocally defined in terms of Majorana states. For Δ ≫TK, the destruction of Kondo screening by superconductivity implies a 4 π -periodic Josephson current-phase relation. Using a strong-coupling analysis in the opposite regime Δ ≪TK, we find a 6 π -periodic Josephson relation for three leads, with critical current Ic≈e Δ2/ℏTK, corresponding to the transfer of fractionalized charges e*=2 e /3 .
Analysis techniques for background rejection at the MAJORANA DEMONSTRATOR
Cuesta, C; Abgrall, N.; Arnquist, I. J.; Avignone, III, F. T.; Barabash, A.S.; Bertrand, F. E.; Bradley, A. W.; Brudanin, V.; Busch, M.; Byram, D.; Caldwell, A. S.; Chan, Y-D; Christofferson, C. D.; Detwiler, J. A.; Efremenko, Yu.; Ejiri, H.; Elliott, S. R.; Galindo-Uribarri, A.; Gilliss, T.; Green, M. P.; Gruszko, J; Guinn, I S; Guiseppe, V E; Henning, R.; Howard, S.; Howe, M. A.; Keeter, K.J.; Kidd, M. F.; Konovalov, S.I.; Kouzes, R. T.; LaFerriere, B. D.; Leon, J.; MacMullin, J.; Meijer, S. J.; Orrell, J. L.; O'Shaughnessy, C.; Radford, D. C.; Rager, J.; Robertson, R.G.H.; Romero-Romero, E.; Snyder, N; Suriano, A. M.; Tedeschi, D; Trimble, J. E.; Vasilyev, S.; Vetter, K. [University of California et al.
2015-01-01
The MAJORANA Collaboration is constructing the MAJORANA DEMONSTRATOR, an ultra-low background, 40-kg modular HPGe detector array to search for neutrinoless double beta decay in Ge-76. In view of the next generation of tonne-scale Ge-based 0 nu beta beta-decay searches that will probe the neutrino mass scale in the inverted-hierarchy region, a major goal of the MAJORANA DEMONSTRATOR is to demonstrate a path forward to achieving a background rate at or below 1 count/tonne/year in the 4 keV region of interest around the Q-value at 2039 keV. The background rejection techniques to be applied to the data include cuts based on data reduction, pulse shape analysis, event coincidences, and time correlations. The Point Contact design of the DEMONSTRATOR's germanium detectors allows for significant reduction of gamma background.
Dislocation Majorana zero modes in perovskite oxide 2DEG
Chung, Suk Bum; Chan, Cheung; Yao, Hong
2016-01-01
Much of the current experimental efforts for detecting Majorana zero modes have been centered on probing the boundary of quantum wires with strong spin-orbit coupling. The same type of Majorana zero mode can also be realized at crystalline dislocations in 2D superconductors with the nontrivial weak topological indices. Unlike at an Abrikosov vortex, at such a dislocation, there is no other low-lying midgap state than the Majorana zero mode so that it avoids usual complications encountered in experimental detections such as scanning tunneling microscope (STM) measurements. We will show that, using the anisotropic dispersion of the t2g orbitals of Ti or Ta atoms, such a weak topological superconductivity can be realized when the surface two-dimensional electronic gas (2DEG) of SrTiO3 or KTaO3 becomes superconducting, which can occur through either intrinsic pairing or proximity to existing s-wave superconductors. PMID:27139319
Landau Levels of Majorana Fermions in a Spin Liquid.
Rachel, Stephan; Fritz, Lars; Vojta, Matthias
2016-04-22
Majorana fermions, originally proposed as elementary particles acting as their own antiparticles, can be realized in condensed-matter systems as emergent quasiparticles, a situation often accompanied by topological order. Here we propose a physical system which realizes Landau levels-highly degenerate single-particle states usually resulting from an orbital magnetic field acting on charged particles-for Majorana fermions. This is achieved in a variant of a quantum spin system due to Kitaev which is distorted by triaxial strain. This strained Kitaev model displays a spin-liquid phase with charge-neutral Majorana-fermion excitations whose spectrum corresponds to that of Landau levels, here arising from a tailored pseudomagnetic field. We show that measuring the dynamic spin susceptibility reveals the Landau-level structure by a remarkable mechanism of probe-induced bound-state formation.
Dislocation Majorana zero modes in perovskite oxide 2DEG.
Chung, Suk Bum; Chan, Cheung; Yao, Hong
2016-05-03
Much of the current experimental efforts for detecting Majorana zero modes have been centered on probing the boundary of quantum wires with strong spin-orbit coupling. The same type of Majorana zero mode can also be realized at crystalline dislocations in 2D superconductors with the nontrivial weak topological indices. Unlike at an Abrikosov vortex, at such a dislocation, there is no other low-lying midgap state than the Majorana zero mode so that it avoids usual complications encountered in experimental detections such as scanning tunneling microscope (STM) measurements. We will show that, using the anisotropic dispersion of the t2g orbitals of Ti or Ta atoms, such a weak topological superconductivity can be realized when the surface two-dimensional electronic gas (2DEG) of SrTiO3 or KTaO3 becomes superconducting, which can occur through either intrinsic pairing or proximity to existing s-wave superconductors.
Dislocation Majorana zero modes in perovskite oxide 2DEG
NASA Astrophysics Data System (ADS)
Chung, Suk Bum; Chan, Cheung; Yao, Hong
2016-05-01
Much of the current experimental efforts for detecting Majorana zero modes have been centered on probing the boundary of quantum wires with strong spin-orbit coupling. The same type of Majorana zero mode can also be realized at crystalline dislocations in 2D superconductors with the nontrivial weak topological indices. Unlike at an Abrikosov vortex, at such a dislocation, there is no other low-lying midgap state than the Majorana zero mode so that it avoids usual complications encountered in experimental detections such as scanning tunneling microscope (STM) measurements. We will show that, using the anisotropic dispersion of the t2g orbitals of Ti or Ta atoms, such a weak topological superconductivity can be realized when the surface two-dimensional electronic gas (2DEG) of SrTiO3 or KTaO3 becomes superconducting, which can occur through either intrinsic pairing or proximity to existing s-wave superconductors.
Electrically tunable topological superconductivity and Majorana fermions in two dimensions
NASA Astrophysics Data System (ADS)
Wang, Jing
2016-12-01
The external controllability of topological superconductors and Majorana fermions would be important both for fundamental and practical interests. Here we predict the electric-field control of Majorana fermions in two-dimensional topological superconductors utilizing a topological insulator thin-film proximity coupled to a conventional s -wave superconductor. With ferromagnetic ordering, the tunable structure inversion asymmetry by vertical electric field could induce topological quantum phase transition and realize a chiral topological superconductor state. A zero-energy Majorana bound state appears at the boundary of an applied electric-field spot, which can be observed by scanning tunneling microscopy. Furthermore, the structure inversion asymmetry could also enlarge the helical topological superconductor state in the phase diagram, making the realization of such an exotic state more feasible. The electrical control of topological phases could further apply to van der Waals materials such as two-dimensional transition-metal dichalcogenides.
Majorana fermion exchange in strictly one-dimensional structures
NASA Astrophysics Data System (ADS)
Chiu, Ching-Kai; Vazifeh, M. M.; Franz, M.
2015-04-01
It is generally thought that the adiabatic exchange of two identical particles is impossible in one spatial dimension. Here we describe a simple protocol that permits the adiabatic exchange of two Majorana fermions in a one-dimensional topological superconductor wire. The exchange relies on the concept of “Majorana shuttle” whereby a π domain wall in the superconducting order parameter which hosts a pair of ancillary majoranas delivers one zero mode across the wire while the other one tunnels in the opposite direction. The method requires some tuning of parameters and does not, therefore, enjoy full topological protection. The resulting exchange statistics, however, remain non-Abelian for a wide range of parameters that characterize the exchange.
Fingerprints of Majorana fermions in spin-resolved subgap spectroscopy
NASA Astrophysics Data System (ADS)
Chirla, Razvan; Moca, Cǎtǎlin Paşcu
2016-07-01
When a strongly correlated quantum dot is tunnel coupled to a superconductor, it leads to the formation of Shiba bound states inside the superconducting gap. They have been measured experimentally in a superconductor-quantum dot-normal lead setup. Side coupling the quantum dot to a topological superconducting wire that supports Majorana bound states at its ends, drastically affects the structure of the Shiba states and induces supplementary in-gap states. The anomalous coupling between the Majorana bound states and the quantum dot gives rise to a characteristic imbalance in the spin-resolved spectral functions for the dot operators. These are clear fingerprints for the existence of Majorana fermions and they can be detected experimentally in transport measurements. In terms of methods employed, we have used analytical approaches combined with the numerical renormalization group approach.
Analysis techniques for background rejection at the Majorana Demonstrator
Cuestra, Clara; Rielage, Keith Robert; Elliott, Steven Ray; Xu, Wenqin; Goett, John Jerome III
2015-06-11
The MAJORANA Collaboration is constructing the MAJORANA DEMONSTRATOR, an ultra-low background, 40-kg modular HPGe detector array to search for neutrinoless double beta decay in ^{76}Ge. In view of the next generation of tonne-scale Ge-based 0νββ-decay searches that will probe the neutrino mass scale in the inverted-hierarchy region, a major goal of the MAJORANA DEMONSTRATOR is to demonstrate a path forward to achieving a background rate at or below 1 count/tonne/year in the 4 keV region of interest around the Q-value at 2039 keV. The background rejection techniques to be applied to the data include cuts based on data reduction, pulse shape analysis, event coincidences, and time correlations. The Point Contact design of the DEMONSTRATOR's germanium detectors allows for significant reduction of gamma background.
Analysis techniques for background rejection at the MAJORANA DEMONSTRATOR
Cuesta, C.; Buuck, M.; Detwiler, J. A.; Gruszko, J.; Guinn, I. S.; Leon, J.; Robertson, R. G. H.; Abgrall, N.; Bradley, A. W.; Chan, Y-D.; Mertens, S.; Poon, A. W. P.; Arnquist, I. J.; Hoppe, E. W.; Kouzes, R. T.; LaFerriere, B. D.; Orrell, J. L.; Avignone, F. T.; Baldenegro-Barrera, C. X.; Bertrand, F. E.; and others
2015-08-17
The MAJORANA Collaboration is constructing the MAJORANA DEMONSTRATOR, an ultra-low background, 40- kg modular HPGe detector array to search for neutrinoless double beta decay in {sup 76}Ge. In view of the next generation of tonne-scale Ge-based 0νβ β-decay searches that will probe the neutrino mass scale in the inverted-hierarchy region, a major goal of the MAJORANA DEMONSTRATOR is to demonstrate a path forward to achieving a background rate at or below 1 count/tonne/year in the 4 keV region of interest around the Q-value at 2039 keV. The background rejection techniques to be applied to the data include cuts based on data reduction, pulse shape analysis, event coincidences, and time correlations. The Point Contact design of the DEMONSTRATOR’s germanium detectors allows for significant reduction of gamma background.
On Majorana Representations of A 6 and A 7
NASA Astrophysics Data System (ADS)
Ivanov, A. A.
2011-10-01
The Majorana representations of groups were introduced in Ivanov (The Monster Group and Majorana Involutions, 2009) by axiomatising some properties of the 2 A-axial vectors of the 196 884-dimensional Monster algebra, inspired by the sensational classification of such representations for the dihedral groups achieved by Sakuma (Int Math Res Notes, 2007). This classification took place in the heart of the theory of Vertex Operator Algebras and expanded earlier results by Miyamoto (J Alg 268:653-671, 2003). Every subgroup G of the Monster which is generated by its intersection with the conjugacy class of 2 A-involutions possesses the (possibly unfaithful) Majorana representation obtained by restricting to G the action of the Monster on its algebra. This representation of G is said to be based on an embedding of G in the Monster. So far the Majorana representations have been classified for the groups G isomorphic to the symmetric group S 4 of degree 4 (Ivanov et al. in J Alg 324:2432-2463, 2010), the alternating group A 5 of degree 5 (Ivanov AA, Seress Á in Majorana Representations of A 5, 2010), and the general linear group GL 3(2) in dimension 3 over the field of two elements (Ivanov AA, Shpectorov S in Majorana Representations of L 3(2), 2010). All these representations are based on embeddings in the Monster of either the group G itself or of its direct product with a cyclic group of order 2. The dimensions and shapes of these representations are given in the following table: "What is our life? A game!" (A.S. Pushkin, "The Queen of Spades")
Study of Majorana fermionic dark matter
NASA Astrophysics Data System (ADS)
Chua, Chun-Khiang; Wong, Gwo-Guang
2016-08-01
We construct a generic model of Majorana fermionic dark matter (DM). Starting with two Weyl spinor multiplets η1 ,2˜(I ,∓Y ) coupled to the Standard Model Higgs, six additional Weyl spinor multiplets with (I ±1 /2 ,±(Y ±1 /2 )) are needed in general. It has 13 parameters in total, five mass parameters and eight Yukawa couplings. The DM sector of the minimal supersymmetric Standard Model is a special case of the model with (I ,Y )=(1 /2 ,1 /2 ). Therefore, this model can be viewed as an extension of the neutralino DM sector. We consider three typical cases: the neutralinolike, the reduced, and the extended cases. For each case, we survey the DM mass mχ in the range of (1,2500) GeV by random sampling from the model parameter space and study the constraints from the observed DM relic density; the direct search of LUX, XENON100, and PICO experiments; and the indirect search of Fermi-LAT data. We investigate the interplay of these constraints and the differences among these cases. It is found that the direct detection of spin-independent DM scattering off nuclei and the indirect detection of DM annihilation to the W+W- channel will be more sensitive to the DM searches in the near future. The allowed mass for finding H ˜-, B ˜-, W ˜-, and non-neutralino-like DM particles and the predictions on ⟨σ (χ χ →Z Z ,Z H ,t t ¯)v ⟩ in the indirect search are given.
A Memory of Majorana Modes through Quantum Quench
Chung, Ming-Chiang; Jhu, Yi-Hao; Chen, Pochung; Mou, Chung-Yu; Wan, Xin
2016-01-01
We study the sudden quench of a one-dimensional p-wave superconductor through its topological signature in the entanglement spectrum. We show that the long-time evolution of the system and its topological characterization depend on a pseudomagnetic field Reff(k). Furthermore, Reff(k) connects both the initial and the final Hamiltonians, hence exhibiting a memory effect. In particular, we explore the robustness of the Majorana zero-mode and identify the parameter space in which the Majorana zero-mode can revive in the infinite-time limit. PMID:27389657
Teleportation-based quantum information processing with Majorana zero modes
NASA Astrophysics Data System (ADS)
Vijay, Sagar; Fu, Liang
2016-12-01
We present a measurement-based scheme for performing braiding operations on Majorana zero modes in mesoscopic superconductor islands and for detecting their non-Abelian statistics without moving or hybridizing them. In our scheme for "braiding without braiding", the topological qubit encoded in any pair of well-separated Majorana zero modes is read out from the transmission phase shift in electron teleportation through the island in the Coulomb-blockade regime. We propose experimental setups to measure the teleportation phase shift via conductance in an electron interferometer or persistent current in a closed loop.
Low Background Signal Readout Electronics for the MAJORANA DEMONSTRATOR
Guinn, I.; Abgrall, N.; Avignone, III, F. T.; Efremenko, Yuri; Galindo-Uribarri, A; Green, M. P.; Radford, D. C.; Romero-Romero, E.; White, B. R.; Wilkerson, J. F.; Majorana,
2015-01-01
The MAJORANA DEMONSTRATOR is a planned 40 kg array of Germanium detectors intended to demonstrate the feasibility of constructing a tonne-scale experiment that will seek neutrinoless double beta decay (0 nu beta beta) in Ge-76. Such an experiment would require backgrounds of less than 1 count/tonne-year in the 4 keV region of interest around the 2039 keV Q-value of the beta beta decay. Designing low-noise electronics, which must be placed in close proximity to the detectors, presents a challenge to reaching this background target. This paper will discuss the MAJORANA collaboration's solutions to some of these challenges.
Discovering the Majorana neutrino: The next generation of experiments
Winslow, L. A.
2015-07-15
The discovery of a Majorana neutrino would be revolutionary with far-reaching consequences in both particle physics and cosmology. The only feasible experiments to determine the Majorana nature of the neutrino are searches for neutrinoless double-beta decay. The next generation of double-beta decay experiments are being prepared. The general goal is to search for neutrinoless double-beta decay throughout the parameter space corresponding to the inverted hierarchy for neutrino mass. There are a several strong proposals for how to achieve this goal. The status of these efforts is reviewed.
Distinguishing between Dirac and Majorana neutrinos withtwo-particle interferometry
Gutierrez, Thomas D.
2006-03-02
Two-particle interferometry, a second-order interferenceeffect, is explored as another possible tool to distinguish betweenmassive Dirac and Majorana neutrinos. A simple theoretical framework isdiscussed in the context of several gedanken experiments. The method canin principle provide both the mass scale and the quantum nature of theneutrino for a certain class of incoherent left-handed sourcecurrents.
The Majorana Demonstrator Neutrinoless Double-beta Decay Experiment
NASA Astrophysics Data System (ADS)
Guiseppe, V. E.
2012-03-01
Neutrinoless double-beta decay searches play a major role in determining the nature of neutrinos, the existence of a lepton violating process, and the effective Majorana neutrino mass. The Majorana Collaboration is assembling an array of HPGe detectors to search for neutrinoless double-beta decay in ^76Ge. Our proposed method uses the well-established technique of searching for neutrinoless double-beta decay in high purity Ge-diode radiation detectors that play both roles of source and detector. The use of p-type point contact Ge detectors present advances in background rejection and a significantly lower energy threshold than conventional Ge detectors. The lower energy threshold opens up a broader and exciting physics program including searches for dark matter and axions concurrent with the double-beta decay search. Initially, Majorana is constructing a prototype module to demonstrate the potential of a future 1-tonne experiment. The status and potential physics reach of the Majorana Demonstrator module will be presented.
The Majorana Double Beta Decay Experiment: Present Status
Aguayo, Estanislao; Avignone, Frank T.; Back, Henning O.; Barabash, Alexander S.; Beene, Jim; Bergevin, M.; Bertrand, F.; Boswell, M.; Brudanin, V.; Busch, Matthew; Chan, Yuen-Dat; Christofferson, C. D.; Collar, J. I.; Combs, Dustin C.; Cooper, R. J.; Detwiler, Jason A.; Doe, Peter J.; Efremenko, Yuri; Egorov, Viatcheslav; Ejiri, H.; Elliott, S. R.; Esterline, James H.; Fast, James E.; Fields, N.; Finnerty, P.; Fraenkle, Florian; Gehman, Victor M.; Giovanetti, G. K.; Green, M. P.; Guiseppe, V. E.; Gusey, K.; Hallin, A. L.; Hazama, R.; Henning, Reyco; Hime, Andrew; Hoppe, Eric W.; Horton, Mark; Howard, Stanley; Howe, M. A.; Johnson, R. A.; Keeter, K.; Keller, C.; Kidd, M. F.; Knecht, A.; Kochetov, Oleg; Konovalov, S.; Kouzes, Richard T.; Laferriere, Brian D.; LaRoque, B. H.; Leon, Jonathan D.; Leviner, L.; Loach, J. C.; MacMullin, S.; Marino, Michael G.; Martin, R. D.; Mei, Dong-Ming; Merriman, Jason H.; Miller, M. L.; Mizouni, Leila; Nomachi, Masaharu; Orrell, John L.; Overman, Nicole R.; Phillips II, D. G.; Poon, Alan; Perumpilly, Gopakumar; Prior, Gersende; Radford, D. C.; Rielage, Keith; Robertson, R. G. H.; Ronquest, M. C.; Schubert, Alexis G.; Shima, T.; Shirchenko, M.; Snavely, Kyle J.; Steele, David; Strain, J.; Thomas, K.; Timkin, V.; Tornow, W.; Vanyushin, I.; Varner, R. L.; Vetter, Kai; Vorren, Kris R.; Wilkerson, J. F.; Yakushev, E.; Young, A.; Yu, Chang-Hong; Yumatov, Vladimir; Zhang, C.
2013-06-01
The Majorana collaboration is actively pursuing research and development aimed at a tonne-scale 76Ge neutrinoless double-beta decay experiment, an R&D effort that will field approximately 40 kg of germanium detectors with mixed enrichment levels. This article provides a status update on the construction of the Demonstrator
Pseudo-Symmetry and Majorana Operators in pf-Shell
Valencia, J. P.; Wu, H. C.
2007-10-26
The Majorana operator of the pseudo ds-shell preserves the SU-tilde(4) symmetry, and in a unified manner it reproduces reasonably well the ground state energies of the nine nuclei in this shell. The study of {beta} decay in the same shell provides further support for the SU-tilde(4) symmetry.
Conductance fingerprint of Majorana fermions in the topological Kondo effect
NASA Astrophysics Data System (ADS)
Galpin, Martin R.; Mitchell, Andrew K.; Temaismithi, Jesada; Logan, David E.; Béri, Benjamin; Cooper, Nigel R.
2014-01-01
We consider an interacting nanowire/superconductor heterostructure attached to metallic leads. The device is described by an unusual low-energy model involving spin-1 conduction electrons coupled to a nonlocal spin-1/2 Kondo impurity built from Majorana fermions. The topological origin of the resulting Kondo effect is manifest in distinctive non-Fermi-liquid (NFL) behavior, and the existence of Majorana fermions in the device is demonstrated unambiguously by distinctive conductance line shapes. We study the physics of the model in detail, using the numerical renormalization group, perturbative scaling, and Abelian bosonization. In particular, we calculate the full scaling curves for the differential conductance in ac and dc fields, onto which experimental data should collapse. Scattering t matrices and thermodynamic quantities are also calculated, recovering asymptotes from conformal field theory. We show that the NFL physics is robust to asymmetric Majorana-lead couplings, and here we uncover a duality between strong and weak coupling. The NFL behavior is understood physically in terms of competing Kondo effects. The resulting frustration is relieved by inter-Majorana coupling which generates a second crossover to a regular Fermi liquid.
Majorana spectroscopy of three-dimensional Kitaev spin liquids
NASA Astrophysics Data System (ADS)
Smith, A.; Knolle, J.; Kovrizhin, D. L.; Chalker, J. T.; Moessner, R.
2016-06-01
We analyze the dynamical response of a range of three-dimensional Kitaev quantum spin liquids, using lattice models chosen to explore the different possible low-energy spectra for gapless Majorana fermions, with either Fermi surfaces, nodal lines, or Weyl points. We find that the behavior of the dynamical structure factor is distinct in all three cases, reflecting the quasiparticle density of states in two fundamentally different ways. First, the low-energy response is either straightforwardly related to the power with which the low-energy density of states vanishes; or for a nonvanishing density of states, to the phase shifts encountered in the corresponding x-ray edge problem, whose phenomenology we extend to the case of Majorana fermions. Second, at higher energies, there is a rich fine structure, determined by microscopic features of the Majorana spectrum. Our theoretical results test the usefulness of inelastic neutron scattering as a probe of these quantum spin liquids: we find that although spin flips fractionalize, the main features of the dynamical spin response nevertheless admit straightforward interpretations in terms of Majorana and flux loop excitations.
Probing the antisymmetric Fano interference assisted by a Majorana fermion
NASA Astrophysics Data System (ADS)
Dessotti, F. A.; Ricco, L. S.; de Souza, M.; Souza, F. M.; Seridonio, A. C.
2014-11-01
As the Fano effect is an interference phenomenon where tunneling paths compete for the electronic transport, it becomes a probe to catch fingerprints of Majorana fermions lying on condensed matter systems. In this work, we benefit of this mechanism by proposing as a route for that an Aharonov-Bohm-like interferometer composed by two quantum dots, being one of them coupled to a Majorana bound state, which is attached to one of the edges of a semi-infinite Kitaev wire within the topological phase. By changing the Fermi energy of the leads and the symmetric detuning of the levels for the dots, we show that opposing Fano regimes result in a transmittance characterized by distinct conducting and insulating regions, which are fingerprints of an isolated Majorana quasiparticle. Furthermore, we show that the maximum fluctuation of the transmittance as a function of the detuning is half for a semi-infinite wire, while it corresponds to the unity for a finite system. The setup proposed here constitutes an alternative experimental tool to detect Majorana excitations.
Majorana edge modes in Kitaev model on honeycomb lattice
NASA Astrophysics Data System (ADS)
Thakurathi, Manisha; Sengupta, Krishnendu; Sen, Diptiman
2015-03-01
We study the Majorana modes, both equilibrium and Floquet, which can appear at the edges of the Kitaev model on the honeycomb lattice. We first present the analytical solutions known for the equilibrium Majorana edge modes for both zigzag and armchair edges of a semi-infinite Kitaev model and chart the parameter regimes of the model in which they appear. We then examine how edge modes can be generated if the Kitaev coupling on the bonds perpendicular to the edge is varied periodically in time as periodic δ-function kicks. We derive a general condition for the appearance and disappearance of the Floquet edge modes as a function of the drive frequency for a generic d-dimensional integrable system. We confirm this general condition for the Kitaev model with a finite width by mapping it to a one-dimensional model. Our numerical and analytical study of this problem shows that Floquet Majorana modes can appear on some edges in the kicked system even when the corresponding equilibrium Hamiltonian has no Majorana mode solutions on those edges. We support our analytical studies by numerics for finite sized system which show that periodic kicks can generate modes at the edges and the corners of the lattice. We thank CSIR, India and DST, India for financial support.
Probing the antisymmetric Fano interference assisted by a Majorana fermion
Dessotti, F. A.; Ricco, L. S.; Souza, M. de; Souza, F. M.; Seridonio, A. C.
2014-11-07
As the Fano effect is an interference phenomenon where tunneling paths compete for the electronic transport, it becomes a probe to catch fingerprints of Majorana fermions lying on condensed matter systems. In this work, we benefit of this mechanism by proposing as a route for that an Aharonov-Bohm-like interferometer composed by two quantum dots, being one of them coupled to a Majorana bound state, which is attached to one of the edges of a semi-infinite Kitaev wire within the topological phase. By changing the Fermi energy of the leads and the symmetric detuning of the levels for the dots, we show that opposing Fano regimes result in a transmittance characterized by distinct conducting and insulating regions, which are fingerprints of an isolated Majorana quasiparticle. Furthermore, we show that the maximum fluctuation of the transmittance as a function of the detuning is half for a semi-infinite wire, while it corresponds to the unity for a finite system. The setup proposed here constitutes an alternative experimental tool to detect Majorana excitations.
Observing Majorana bound states of Josephson vortices in topological superconductors
Grosfeld, Eytan; Stern, Ady
2011-01-01
In recent years there has been an intensive search for Majorana fermion states in condensed matter systems. Predicted to be localized on cores of vortices in certain nonconventional superconductors, their presence is known to render the exchange statistics of bulk vortices non-Abelian. Here we study the equations governing the dynamics of phase solitons (fluxons) in a Josephson junction in a topological superconductor. We show that the fluxon will bind a localized zero energy Majorana mode and will consequently behave as a non-Abelian anyon. The low mass of the fluxon, as well as its experimentally observed quantum mechanical wave-like nature, will make it a suitable candidate for vortex interferometry experiments demonstrating non-Abelian statistics. We suggest two experiments that may reveal the presence of the zero mode carried by the fluxon. Specific experimental realizations will be discussed as well. PMID:21730165
Two-Dimensional Platform for Networks of Majorana Bound States
NASA Astrophysics Data System (ADS)
Hell, Michael; Leijnse, Martin; Flensberg, Karsten
2017-03-01
We model theoretically a two-dimensional electron gas (2DEG) covered by a superconductor and demonstrate that topological superconducting channels are formed when stripes of the superconducting layer are removed. As a consequence, Majorana bound states (MBSs) are created at the ends of the stripes. We calculate the topological invariant and energy gap of a single stripe, using realistic values for an InAs 2DEG proximitized by an epitaxial Al layer. We show that the topological gap is enhanced when the structure is made asymmetric. This can be achieved either by imposing a phase difference (by driving a supercurrent or using a magnetic-flux loop) over the strip or by replacing one superconductor by a metallic gate. Both strategies also enable control over the MBS splitting, thereby facilitating braiding and readout schemes based on controlled fusion of MBSs. Finally, we outline how a network of Majorana stripes can be designed.
Study of the ( μ-, e +) reaction mediated by Majorana neutrinos
NASA Astrophysics Data System (ADS)
Vergados, J. D.; Ericson, M.
1982-02-01
The exotic lepton violating ( μ-, e +) reaction has been studied in a gauge theory model which assumes the existence of a Majorana neutral lepton. In addition to the usual mechanism involving only two nucleons, the reaction mechanisms which consider a virtual Δ++ present in the nucleus or pions in flight between the interacting nucleons have also been included. The total ( μ-, e +) branching ratio was computed as a function of the various parameters of the theory. It was found to be very sensitively dependent on the mass mσ of the Majorana particle and it becomes very small for mσ > 10 GeV/ c2. The dependence of the branching ratio on the other parameters of the theory is also discussed.
Fermion fractionalization to Majorana fermions in a dimerized Kitaev superconductor
NASA Astrophysics Data System (ADS)
Wakatsuki, Ryohei; Ezawa, Motohiko; Tanaka, Yukio; Nagaosa, Naoto
2014-07-01
We study theoretically a one-dimensional dimerized Kitaev superconductor model which belongs to BDI class with time-reversal, particle-hole, and chiral symmetries. There are two sources of the particle-hole symmetry, i.e., the sublattice symmetry and superconductivity. Accordingly, we define two types of topological numbers with respect to the chiral indices of normal and Majorana fermions, which offers an ideal laboratory to examine the interference between the two different physics within the same symmetry class. Phase diagram, zero-energy bound states, and conductance at normal metal/superconductor junction of this model are unveiled from this viewpoint. Especially, the electron fractionalization to the Majorana fermions showing the splitting of the local density of states is realized at the soliton of the dimerization in this model.
Fermion Fractionalization to Majorana Fermions in Dimerized Kitaev Superconductor
NASA Astrophysics Data System (ADS)
Wakatsuki, Ryohei; Ezawa, Motohiko; Tanaka, Yukio; Nagaosa, Naoto
2015-03-01
We study theoretically a one-dimensional dimerized Kitaev superconductor model which belongs to BDI class with time-reversal, particle-hole, and chiral symmetries. There are two sources of the particle-hole symmetry, i.e., the sublattice symmetry and superconductivity. Accordingly, we define two types of topological numbers with respect to the chiral indices of normal and Majorana fermions, which offers an ideal laboratory to examine the interference between the two different physics within the same symmetry class. Phase diagram, zero-energy bound states, and conductance at normal metal/superconductor junction of this model are unveiled from this viewpoint. Especially, the electron fractionalization to the Majorana fermions showing the splitting of the local density of states is realized at the soliton of the dimerization in this model.
Low background signal readout electronics for the Majorana Demonstrator
Guinn, I.; Abgrall, N.; Avignone, F. T.; ...
2015-05-01
The Majorana Demonstrator is a planned 40 kg array of Germanium detectors intended to demonstrate the feasibility of constructing a tonne-scale experiment that will seek neutrinoless double beta decay (0νββ) in 76Ge. In such an experiment we require backgrounds of less than 1 count/tonne-year in the 4 keV region of interest around the 2039 keV Q-value of the ββ decay. Moreover, designing low-noise electronics, which must be placed in close proximity to the detectors, presents a challenge to reaching this background target. Finally, this paper will discuss the Majorana collaboration's solutions to some of these challenges.
Low background signal readout electronics for the Majorana Demonstrator
Guinn, I.; Abgrall, N.; Avignone, F. T.; Barabash, A. S.; Bertrand, F. E.; Brudanin, V.; Busch, M.; Buuck, M.; Byram, D.; Caldwell, A. S.; Chan, Y-D; Christofferson, C. D.; Cuesta, C.; Detwiler, J. A.; Efremenko, Yu; Ejiri, H.; Elliott, S. R.; Galindo-Uribarri, A.; Giovanetti, G. K.; Goett, J.; Green, M. P.; Gruszko, J.; Guiseppe, V. E.; Henning, R.; Hoppe, E. W.; Howard, S.; Howe, M. A.; Jasinski, B. R.; Keeter, K. J.; Kidd, M. F.; Konovalov, S. I.; Kouzes, R. T.; LaFerriere, B. D.; Leon, J.; MacMullin, J.; Martin, R. D.; Meijer, S. J.; Mertens, S.; Orrell, J. L.; O'Shaughnessy, C.; Overman, N. R.; Poon, A. W. P.; Radford, D. C.; Rager, J.; Rielage, K.; Robertson, R. G. H.; Romero-Romero, E.; Ronquest, M. C.; Shanks, B.; Shirchenko, M.; Snyder, N.; Suriano, A. M.; Tedeschi, D.; Trimble, J. E.; Varner, R. L.; Vasilyev, S.; Vetter, K.; Vorren, K.; White, B. R.; Wilkerson, J. F.; Wiseman, C.; Xu, W.; Yakushev, E.; Yu, C-H; Yumatov, V.
2015-05-01
The Majorana Demonstrator is a planned 40 kg array of Germanium detectors intended to demonstrate the feasibility of constructing a tonne-scale experiment that will seek neutrinoless double beta decay (0νββ) in ^{76}Ge. In such an experiment we require backgrounds of less than 1 count/tonne-year in the 4 keV region of interest around the 2039 keV Q-value of the ββ decay. Moreover, designing low-noise electronics, which must be placed in close proximity to the detectors, presents a challenge to reaching this background target. Finally, this paper will discuss the Majorana collaboration's solutions to some of these challenges.
Manipulation of Majorana states in X-junction geometries
NASA Astrophysics Data System (ADS)
Aristov, D. N.; Gutman, D. B.
2016-08-01
We study quantum manipulation based on four Majorana bound states in X-junction geometry. The parameter space of this setup is bigger than of the previously studied Y-junction and is described by SO(4) symmetry group. In order for quantum computation to be dephasing free, two Majorana states have to stay degenerate at all times. We find a condition necessary for that and compute the Berry’s phase, 2α , accumulated during the manipulation. We construct simple protocols for the variety of values of α, including π /8 needed for the purposes of quantum computation. Although the manipulations in general X-junction geometry are not topologically protected, they may prove to be a feasible compromise for aims of quantum computation.
Milestones toward Majorana-based quantum computing (Conference Presentation)
NASA Astrophysics Data System (ADS)
Mishmash, Ryan V.; Aasen, David; Hell, Michael; Higginbotham, Andrew; Danon, Jeroen; Leijnse, Martin; Jespersen, Thomas S.; Folk, Joshua A.; Marcus, Charles M.; Flensberg, Karsten; Alicea, Jason
2016-10-01
We introduce a scheme for preparation, manipulation, and readout of Majorana zero modes in semiconducting wires with mesoscopic superconducting islands. Our approach synthesizes recent advances in materials growth with tools commonly used in quantum-dot experiments, including gate-control of tunnel barriers and Coulomb effects, charge sensing, and charge pumping. We outline a sequence of milestones interpolating between zero-mode detection and quantum computing that includes (1) detection of fusion rules for non-Abelian anyons using either proximal charge sensors or pumped current; (2) validation of a prototype topological qubit; and (3) demonstration of non-Abelian statistics by braiding in a branched geometry. The first two milestones require only a single wire with two islands, and additionally enable sensitive measurements of the system's excitation gap, quasiparticle poisoning rates, residual Majorana zero-mode splittings, and topological-qubit coherence times. These pre-braiding experiments can be adapted to other manipulation and readout schemes as well.
Supersymmetry between Jackiw-Nair and Dirac-Majorana anyons
Horvathy, Peter A.; Valenzuela, Mauricio; Plyushchay, Mikhail S.
2010-06-15
The Jackiw-Nair description of anyons combines spin-1 topologically massive fields with the discrete series representation of the Lorentz algebra, which has fractional spin. In the Dirac-Majorana formulation the spin-1 part is replaced by the spin 1/2 planar Dirac equation. The two models are shown to belong to an N=1 supermultiplet, which carries a super-Poincare symmetry.
Majorana fermion wavefunctions in carbon nanotubes and carbynes
NASA Astrophysics Data System (ADS)
Sadykov, N. R.; Aporoski, A. V.
2017-02-01
Electron properties of semiconducting zigzag carbon nanotubes (CNTs) can be described by two uncoupled Dirac equations of dimension (1+1) for the particle with nonzero mass. The solutions of these equations are two charge-neutral Majorana fields. An analogous equation is obtained for the carbon chains. We use the approach, wherein wavefunction of charged particle is represented as the production of a rapidly oscillating exponent and the slowly varying function amplitude depending on the longitudinal coordinate.
Search for Majorana Fermions in S-Wave Fermionic Superfluids
2016-04-01
spin-momentum coupling, a crucial ingredient for the emergence of topological phases, is currently drawing considerable interest. In previous...sets of physical parameters including temperature, tunneling strength, wire length, magnetic field, and induced SC pairing potential in the SM...nanowire. We conclude that in a finite wire the Majorana splitting energy ∆E, which has non-trivial dependence on these physical parameters, remains
Direct Observation of a Majorana Quasiparticle Heat Capacity in 3He
NASA Astrophysics Data System (ADS)
Bunkov, Y. M.
2014-04-01
The Majorana fermion, which acts as its own antiparticle, was suggested by Majorana in 1937 (Nuovo Cimento 14:171). While no stable particle with Majorana properties has yet been observed, Majorana quasiparticles (QP) may exist at the boundaries of topological insulators. Here we report the preliminary results of direct observation of Majorana QPs by a precise measurements of superfluid 3He heat capacity. The bulk superfluid 3He heat capacity falls exponentially with cooling at the temperatures significantly below the energy gap. Owing to the zero energy gap mode the Majorana heat capacity falls in a power law. The Majorana heat capacity can be larger than bulk one at some temperature, which depends on surface to volume ratio of the experimental cell. Some times ago we developed the Dark matter particles detector (DMD) on a basis of superfluid 3He which is working at the frontier of extremely low temperatures (Winkelmann et al., Nucl. Instrum. Meth. A 559:384-386, 2006). Here we report the observation of zero gap mode of Majorana, follows from the new analyses of DMD heat capacity, published early. We have found a 10 % deviation from the bulk superfluid 3He heat capacity at the temperature of 135 μK. This deviation corresponds well to the theoretical value for Majorana heat capacity at such low temperature. (Note, there were no fitting parameters).
Lee, Minchul; Choi, Mahn-Soo
2014-08-15
We investigate the mesoscopic resistor-capacitor circuit consisting of a quantum dot coupled to spatially separated Majorana fermion modes in a chiral topological superconductor. We find substantially enhanced relaxation resistance due to the nature of Majorana fermions, which are their own antiparticles and are composed of particle and hole excitations in the same abundance. Further, if only a single Majorana mode is involved, the zero-frequency relaxation resistance is completely suppressed due to a destructive interference. As a result, the Majorana mode opens an exotic dissipative channel on a superconductor which is typically regarded as dissipationless due to its finite superconducting gap.
Fault-tolerant quantum random-number generator certified by Majorana fermions
NASA Astrophysics Data System (ADS)
Deng, Dong-Ling; Duan, Lu-Ming
2013-07-01
Braiding of Majorana fermions gives accurate topological quantum operations that are intrinsically robust to noise and imperfection, providing a natural method to realize fault-tolerant quantum information processing. Unfortunately, it is known that braiding of Majorana fermions is not sufficient for the implementation of universal quantum computation. Here we show that topological manipulation of Majorana fermions provides the full set of operations required to generate random numbers by way of quantum mechanics and to certify its genuine randomness through violation of a multipartite Bell inequality. The result opens a perspective to apply Majorana fermions for the robust generation of certified random numbers, which has important applications in cryptography and other related areas.
Detection of Majorana Kramers Pairs Using a Quantum Point Contact
NASA Astrophysics Data System (ADS)
Li, Jian; Pan, Wei; Bernevig, B. Andrei; Lutchyn, Roman M.
2016-07-01
We propose a setup that integrates a quantum point contact (QPC) and a Josephson junction on a quantum spin Hall sample, experimentally realizable in InAs/GaSb quantum wells. The confinement due to both the QPC and the superconductor results in a Kramers pair of Majorana zero-energy bound states when the superconducting phases in the two arms differ by an odd multiple of π across the Josephson junction. We investigate the detection of these Majorana pairs with the integrated QPC, and find a robust switching from normal to Andreev scattering across the edges due to the presence of Majorana Kramers pairs. Such a switching of the current represents a qualitative signature where multiterminal differential conductances oscillate with alternating signs when the external magnetic field is tuned. We show that this qualitative signature is also present in current cross-correlations. Thus, the change of the backscattering current nature affects both conductance and shot noise, the measurement of which offers a significant advantage over quantitative signatures such as conductance quantization in realistic measurements.
Low Background Signal Readout Electronics for the MAJORANA DEMONSTRATOR
Guinn, I.; Abgrall, N.; Arnquist, I. J.; Avignone, III, F. T.; Barabash, A.S.; Bertrand, F. E.; Bradley, A. W.; Brudanin, V.; Busch, M.; Byram, D.; Caldwell, A. S.; Chan, Y-D; Christofferson, C. D.; Cuesta, C; Detwiler, J. A.; Efremenko, M.; Ejiri, H.; Elliott, S. R.; Galindo-Uribarri, A.; Gilliss, T.; Green, M. P.; Gruszko, J; Guiseppe, V E; Henning, R.; Howard, S.; Howe, M. A.; Keeter, K.J.; Kidd, M. F.; Konovalov, S.I.; Kouzes, R. T.; LaFerriere, B. D.; Leon, J.; MacMullin, J.; Meijer, S. J.; Orrell, J. L.; O'Shaughnessy, C.; Radford, D. C.; Rager, J.; Robertson, R.G.H.; Romero-Romero, E.; Snyder, N; Suriano, A. M.; Tedeschi, D; Trimble, J.; Vasilyev, S.; Vetter, K. [University of California Vorren, K. [University of North Carolina et al.
2015-01-01
The MAJORANA Collaboration will seek neutrinoless double beta decay (0 nu beta beta) in Ge-76 using isotopically enriched p-type point contact (PPC) high purity Germanium (HPGe) detectors. A tonne-scale array of HPGe detectors would require background levels below 1 count/ROI-tonne-year in the 4 keV region of interest (ROI) around the 2039 keV Q-value of the decay. In order to demonstrate the feasibility of such an experiment, the MAJORANA DEMONSTRATOR, a 40 kg HPGe detector array, is being constructed with a background goal of <3 counts/ROI-tonne-year, which is expected to scale down to <1 count/ROI-tonne-year for a tonne-scale experiment. The signal readout electronics, which must be placed in close proximity to the detectors, present a challenge toward reaching this background goal. This talk will discuss the materials and design used to construct signal readout electronics with low enough backgrounds for the MAJORANA DEMONSTRATOR.
Majorana edge states in superconductor-noncollinear magnet interfaces
NASA Astrophysics Data System (ADS)
Chen, Wei; Schnyder, Andreas P.
2015-12-01
Through s -d coupling, a superconducting thin film interfaced to a noncollinear magnetic insulator inherits its magnetic order, which may induce unconventional superconductivity that hosts Majorana edge states. We present a unified formalism that covers the cycloidal, helical, and tilted conical order discovered in multiferroics, as well as Bloch and Neel domain walls of ferromagnetic insulators, and show that they induce (px+py )-wave pairing that supports Majorana edge modes. The advantages over one-dimensional proposals are that the Majorana states can exist without fine tuning of the chemical potential, can be stabilized in a much larger parameter space, and can be separated over the distance of long-range noncollinear order that is known to reach a macroscopic scale. A skyrmion spin texture, on the other hand, induces a nonuniform (pr+i pφ )-wave-like pairing under the influence of an emergent electromagnetic field, yielding a vortex state that displays both a bulk persistent current and a topological edge current.
Discriminating Majorana neutrino textures in light of the baryon asymmetry
NASA Astrophysics Data System (ADS)
Borah, Manikanta; Borah, Debasish; Das, Mrinal Kumar
2015-06-01
We study all possible texture zeros in the Majorana neutrino mass matrix which are allowed from neutrino oscillation as well as cosmology data when the charged lepton mass matrix is assumed to take the diagonal form. In the case of one-zero texture, we write down the Majorana phases which are assumed to be equal and the lightest neutrino mass as a function of the Dirac C P phase. In the case of two-zero texture, we numerically evaluate all the three C P phases and lightest neutrino mass by solving four real constraint equations. We then constrain texture zero mass matrices from the requirement of producing correct baryon asymmetry through the mechanism of leptogenesis by assuming the Dirac neutrino mass matrix to be diagonal. Adopting a type I seesaw framework, we consider the C P -violating out of equilibrium decay of the lightest right-handed neutrino as the source of lepton asymmetry. Apart from discriminating between the texture zero mass matrices and light neutrino mass hierarchy, we also constrain the Dirac and Majorana C P phases so that the observed baryon asymmetry can be produced. In two-zero texture, we further constrain the diagonal form of the Dirac neutrino mass matrix from the requirement of producing correct baryon asymmetry.
Electron transport in multiterminal networks of Majorana bound states
NASA Astrophysics Data System (ADS)
Weithofer, Luzie; Recher, Patrik; Schmidt, Thomas L.
2014-11-01
We investigate electron transport through multiterminal networks hosting Majorana bound states (MBS) in the framework of full counting statistics. In particular, we apply our general results to T-shaped junctions of two Majorana nanowires. When the wires are in the topologically nontrivial regime, three MBS are localized near the outer ends of the wires, while one MBS is localized near the crossing point, and when the lengths of the wires are finite adjacent MBS can overlap. We propose a combination of current and cross-correlation measurements to reveal the predicted coupling of four Majoranas in a topological T junction. Interestingly, we show that the elementary transport processes at the central lead are different compared to the outer leads, giving rise to characteristic nonlocal signatures in electronic transport. We find quantitative agreement between our analytical model and numerical simulations of a tight-binding model. Using the numerical simulations, we discuss the effect of weak disorder on the current and the cross-correlation functions.
Majorana metals in spin-orbit entangled quantum matter
NASA Astrophysics Data System (ADS)
Trebst, Simon
2015-03-01
The largely accidental balance of electronic correlations, spin-orbit entanglement, and crystal field effects of 5d transition metal oxides results in a remarkably broad variety of metallic and insulating states. In this talk, we will discuss the physics of spin-orbit entangled j=1/2 Mott insulators whose microscopic description gives rise to three-dimensional variants of the Kitaev model. The analytical tractability of this model allows to study the fractionalization of these moments into Majorana fermions (and a Z2 gauge field) and their emergent collective behavior. We show that the Majorana fermions generically form metallic states who precise character intimately depends on the underlying lattice structure. Examples range from the well known Dirac semimetal of the two-dimensional Kitaev honeycomb model to three-dimensional metals, in which the gapless modes either form a Fermi line or a Fermi surface akin to a conventional metal. We further discuss our recent finding of a Weyl spin liquid - a state with topologically protected Weyl nodes in the bulk and associated Fermi arcs on the surface. Finally, we comment on the thermodynamic and transport signatures of these various Majorana metals. Joint work with M. Hermanns and K. O'Brien.
Low Background Signal Readout Electronics for the Majorana Demonstrator
Guinn, Ian; Rielage, Keith Robert; Elliott, Steven Ray; Xu, Wenqin; Goett, John Jerome III
2015-06-11
The MAJORANA Collaboration will seek neutrinoless double beta decay (0νββ) in ^{76}Ge using isotopically enriched p-type point contact (PPC) high purity Germanium (HPGe) detectors. A tonne-scale array of HPGe detectors would require background levels below 1 count/ROI-tonne-year in the 4 keV region of interest (ROI) around the 2039 keV Q-value of the decay. In order to demonstrate the feasibility of such an experiment, the MAJORANA DEMONSTRATOR, a 40 kg HPGe detector array, is being constructed. The DEMONSTRATOR has a background goal of < 3 counts/ROI-tonne-year, which is expected to scale down to < 1 count/ROI-tonne-year for a one tonne experiment. The signal readout electronics, which must be placed in close proximity to the detectors, present a challenge toward reaching this background goal. This paper discusses the materials and design used to construct signal readout electronics with low enough backgrounds for the MAJORANA DEMONSTRATOR.
Majorana neutrino masses and the neutrinoless double-beta decay
Faessler, A.
2006-12-15
Neutrinoless double-beta decay is forbidden in the Standard Model of electroweak and strong interaction but allowed in most Grand Unified Theories (GUTs). Only if the neutrino is a Majorana particle (identical with its antiparticle) and if it has a mass is neutrinoless double-beta decay allowed. Apart from one claim that the neutrinoless double-beta decay in {sup 76}Ge is measured, one has only upper limits for this transition probability. But even the upper limits allow one to give upper limits for the electron Majorana neutrino mass and upper limits for parameters of GUTs and the minimal R-parity-violating supersymmetric model. One further can give lower limits for the vector boson mediating mainly the right-handed weak interaction and the heavy mainly right-handed Majorana neutrino in left-right symmetric GUTs. For that, one has to assume that the specific mechanism is the leading one for neutrinoless double-beta decay and one has to be able to calculate reliably the corresponding nuclear matrix elements. In the present work, one discusses the accuracy of the present status of calculating of the nuclear matrix elements and the corresponding limits of GUTs and supersymmetric parameters.
Status and Initial Results from the MAJORANA DEMONSTRATOR
NASA Astrophysics Data System (ADS)
Detwiler, Jason
2016-09-01
The MAJORANA DEMONSTRATOR is performing a sensitive search for the neutrinoless double-beta decay of 76Ge using an ultra-low background array of enriched HPGe detectors deployed at the Sanford Underground Research Facility in Lead, SD. This rare process is generically predicted to occur by large classes of beyond-the-Standard-Model theories, and its observation would indicate that lepton number is not a conserved quantity in nature, with implications for the matter-dominance of the universe. The techniques used for the MAJORANA DEMONSTRATOR include selection and production of materials extremely low in natural radioactivity, choice of detector technology enabling active rejection of background, and graded active and passive shielding, which together give a projected background rate that is the lowest among existing techniques. First data from the DEMONSTRATOR is in-hand, and I will present our preliminary background performance and sensitivity both to neutrinoless double-beta decay as well as other physics targets. I will discuss the current detector status and plans for future upgrades, and our ultimate goal to field a much larger array with even lower background that will be sensitive to MAJORANA neutrinos with an inverted mass ordering.
Ising anyons in frustration-free Majorana-dimer models
NASA Astrophysics Data System (ADS)
Ware, Brayden; Son, Jun Ho; Cheng, Meng; Mishmash, Ryan V.; Alicea, Jason; Bauer, Bela
2016-09-01
Dimer models have long been a fruitful playground for understanding topological physics. Here, we introduce a class, termed Majorana-dimer models, wherein bosonic dimers are decorated with pairs of Majorana modes. We find that the simplest examples of such systems realize an intriguing, intrinsically fermionic phase of matter that can be viewed as the product of a chiral Ising theory, which hosts deconfined non-Abelian quasiparticles, and a topological px-i py superconductor. While the bulk anyons are described by a single copy of the Ising theory, the edge remains fully gapped. Consequently, this phase can arise in exactly solvable, frustration-free models. We describe two parent Hamiltonians: one generalizes the well-known dimer model on the triangular lattice, while the other is most naturally understood as a model of decorated fluctuating loops on a honeycomb lattice. Using modular transformations, we show that the ground-state manifold of the latter model unambiguously exhibits all properties of the Ising×(px-i py) theory. We also discuss generalizations with more than one Majorana mode per site, which realize phases related to Kitaev's 16-fold way in a similar fashion.
Low background signal readout electronics for the MAJORANA DEMONSTRATOR
Guinn, I.; Buuck, M.; Cuesta, C.; Detwiler, J. A.; Gruszko, J.; Leon, J.; Robertson, R. G. H.; Abgrall, N.; Bradley, A. W.; Chan, Y-D.; Mertens, S.; Poon, A. W. P.; Arnquist, I. J.; Hoppe, E. W.; Kouzes, R. T.; LaFerriere, B. D.; Orrell, J. L.; Avignone, F. T.; Baldenegro-Barrera, C. X.; Bertrand, F. E.; and others
2015-08-17
The MAJORANA Collaboration will seek neutrinoless double beta decay (0νββ) in {sup 76}Ge using isotopically enriched p-type point contact (PPC) high purity Germanium (HPGe) detectors. A tonne-scale array of HPGe detectors would require background levels below 1 count/ROI-tonne-year in the 4 keV region of interest (ROI) around the 2039 keV Q-value of the decay. In order to demonstrate the feasibility of such an experiment, the MAJORANA DEMONSTRATOR, a 40 kg HPGe detector array, is being constructed with a background goal of < 3 count/ROI-tonne-year, which is expected to scale down to < 1 count/ROI-tonne-year for a tonne-scale experiment. The signal readout electronics, which must be placed in close proximity to the detectors, present a challenge toward reaching this background goal. This talk will discuss the materials and design used to construct signal readout electronics with low enough backgrounds for the MAJORANA DEMONSTRATOR.
The 2017 solar eclipse and Majorana & Allais gravity anomalies
NASA Astrophysics Data System (ADS)
Munera, Hector A.
2017-01-01
Two little known anomalies hint to phenomena beyond current theory. Majorana effect: around 1920 in a series of well-designed experiments with a chemical laboratory balance, Quirino Majorana found in Italy that mercury (Hg) and lead (Pb) might shield terrestrial gravity. Majorana experiments were never repeated by the international scientific community. Instead his results were dismissed on theoretical claims: a) unobserved heating of earth by absorption of gravity, and b) unobserved cyclic lunar perturbation of solar gravity at earth’s surface. However, Majorana critics missed the crucial fact that shielding is not mere absorption, but also scattering, and that atomic number Z of matter in the moon is much lower than Z=80 (Hg) and Z=82 (Pb). From the June 30/1954 solar eclipse onwards, high-quality mechanical gravimeters were used to search for Majorana shielding by the moon. Results are positive, provided that shielding is interpreted as scattering rather than absorption of gravity by moon (H. A. Munera, Physics Essays 24, 428-434, 2011). Allais effect: during the same 1954 eclipse (partial in Paris) Maurice Allais had in operation a sensitive paraconical pendulum for a very different purpose. Surprisingly, the pendulum was perturbed by the eclipse, condition repeated once again in a 1959 solar eclipse, also partial in Paris. During the past sixty years, paraconical, torsion and Foucault pendula, and other mechanical devices, have been used to (dis)confirm Allais effect, but the results are not conclusive thus far. A book edited by this author (Should the laws of gravitation be revised? Apeiron 2011) describes some of those observations. Various unexpected effects, some of them torsional, appear both near the optical shadow, and far away. The Sun-Moon-Earth alignment in a solar eclipse allows detection on the terrestrial surface of the dark matter flow scattered on moon’s surface (flow not hitting earth in other geometries). Rotation of moon may induce
Khachatryan, Vardan
2016-04-27
In this study, a search is performed for heavy Majorana neutrinos (N) decaying into a W boson and a lepton using the CMS detector at the Large Hadron Collider. A signature of two jets and either two same sign electrons or a same sign electron-muon pair is searched for using 19.7 inverse femtobarns of data collected during 2012 in proton-proton collisions at a centre-of-mass energy of 8 TeV. The data are found to be consistent with the expected standard model (SM) background and, in the context of a Type-1 seesaw mechanism, upper limits are set on the cross section timesmore » branching fraction for production of heavy Majorana neutrinos in the mass range between 40 and 500 GeV. The results are additionally interpreted as limits on the mixing between the heavy Majorana neutrinos and the SM neutrinos. In the mass range considered, the upper limits range between 0.00015 - 0.72 for |VeN|2 and 6.6x10-5 - 0.47 for |VeN V*μN|2 / ( |VeN|2 + |VμN|2), where VlN is the mixing element describing the mixing of the heavy neutrino with the SM neutrino of flavour l. These limits are the most restrictive direct limits for heavy Majorana neutrino masses above 200 GeV.« less
NASA Astrophysics Data System (ADS)
Khachatryan, V.; Sirunyan, A. M.; Tumasyan, A.; Adam, W.; Asilar, E.; Bergauer, T.; Brandstetter, J.; Brondolin, E.; Dragicevic, M.; Erö, J.; Flechl, M.; Friedl, M.; Frühwirth, R.; Ghete, V. M.; Hartl, C.; Hörmann, N.; Hrubec, J.; Jeitler, M.; König, A.; Krammer, M.; Krätschmer, I.; Liko, D.; Matsushita, T.; Mikulec, I.; Rabady, D.; Rad, N.; Rahbaran, B.; Rohringer, H.; Schieck, J.; Schöfbeck, R.; Strauss, J.; Treberer-Treberspurg, W.; Waltenberger, W.; Wulz, C.-E.; Mossolov, V.; Shumeiko, N.; Suarez Gonzalez, J.; Alderweireldt, S.; Cornelis, T.; de Wolf, E. A.; Janssen, X.; Knutsson, A.; Lauwers, J.; Luyckx, S.; van de Klundert, M.; van Haevermaet, H.; van Mechelen, P.; van Remortel, N.; van Spilbeeck, A.; Abu Zeid, S.; Blekman, F.; D'Hondt, J.; Daci, N.; de Bruyn, I.; Deroover, K.; Heracleous, N.; Keaveney, J.; Lowette, S.; Moortgat, S.; Moreels, L.; Olbrechts, A.; Python, Q.; Strom, D.; Tavernier, S.; van Doninck, W.; van Mulders, P.; van Onsem, G. P.; van Parijs, I.; Brun, H.; Caillol, C.; Clerbaux, B.; de Lentdecker, G.; Fasanella, G.; Favart, L.; Goldouzian, R.; Grebenyuk, A.; Karapostoli, G.; Lenzi, T.; Léonard, A.; Maerschalk, T.; Marinov, A.; Perniè, L.; Randle-Conde, A.; Seva, T.; Vander Velde, C.; Vanlaer, P.; Yonamine, R.; Zenoni, F.; Zhang, F.; Benucci, L.; Cimmino, A.; Crucy, S.; Dobur, D.; Fagot, A.; Garcia, G.; Gul, M.; McCartin, J.; Ocampo Rios, A. A.; Poyraz, D.; Ryckbosch, D.; Salva, S.; Sigamani, M.; Tytgat, M.; van Driessche, W.; Yazgan, E.; Zaganidis, N.; Basegmez, S.; Beluffi, C.; Bondu, O.; Brochet, S.; Bruno, G.; Caudron, A.; Ceard, L.; de Visscher, S.; Delaere, C.; Delcourt, M.; Favart, D.; Forthomme, L.; Giammanco, A.; Jafari, A.; Jez, P.; Komm, M.; Lemaitre, V.; Mertens, A.; Musich, M.; Nuttens, C.; Perrini, L.; Piotrzkowski, K.; Quertenmont, L.; Selvaggi, M.; Vidal Marono, M.; Beliy, N.; Hammad, G. H.; Aldá Júnior, W. L.; Alves, F. L.; Alves, G. A.; Brito, L.; Correa Martins Junior, M.; Hamer, M.; Hensel, C.; Moraes, A.; Pol, M. E.; Rebello Teles, P.; Belchior Batista Das Chagas, E.; Carvalho, W.; Chinellato, J.; Custódio, A.; da Costa, E. M.; de Jesus Damiao, D.; de Oliveira Martins, C.; Fonseca de Souza, S.; Huertas Guativa, L. M.; Malbouisson, H.; Matos Figueiredo, D.; Mora Herrera, C.; Mundim, L.; Nogima, H.; Prado da Silva, W. L.; Santoro, A.; Sznajder, A.; Tonelli Manganote, E. J.; Vilela Pereira, A.; Ahuja, S.; Bernardes, C. A.; de Souza Santos, A.; Dogra, S.; Fernandez Perez Tomei, T. R.; Gregores, E. M.; Mercadante, P. G.; Moon, C. S.; Novaes, S. F.; Padula, Sandra S.; Romero Abad, D.; Ruiz Vargas, J. C.; Aleksandrov, A.; Hadjiiska, R.; Iaydjiev, P.; Rodozov, M.; Stoykova, S.; Sultanov, G.; Vutova, M.; Dimitrov, A.; Glushkov, I.; Litov, L.; Pavlov, B.; Petkov, P.; Fang, W.; Ahmad, M.; Bian, J. G.; Chen, G. M.; Chen, H. S.; Chen, M.; Cheng, T.; Du, R.; Jiang, C. H.; Leggat, D.; Plestina, R.; Romeo, F.; Shaheen, S. M.; Spiezia, A.; Tao, J.; Wang, C.; Wang, Z.; Zhang, H.; Asawatangtrakuldee, C.; Ban, Y.; Li, Q.; Liu, S.; Mao, Y.; Qian, S. J.; Wang, D.; Xu, Z.; Avila, C.; Cabrera, A.; Chaparro Sierra, L. F.; Florez, C.; Gomez, J. P.; Gomez Moreno, B.; Sanabria, J. C.; Godinovic, N.; Lelas, D.; Puljak, I.; Ribeiro Cipriano, P. M.; Antunovic, Z.; Kovac, M.; Brigljevic, V.; Kadija, K.; Luetic, J.; Micanovic, S.; Sudic, L.; Attikis, A.; Mavromanolakis, G.; Mousa, J.; Nicolaou, C.; Ptochos, F.; Razis, P. A.; Rykaczewski, H.; Finger, M.; Finger, M.; Abdelalim, A. A.; Elkafrawy, T.; Mahmoud, M. A.; Salama, E.; Calpas, B.; Kadastik, M.; Murumaa, M.; Raidal, M.; Tiko, A.; Veelken, C.; Eerola, P.; Pekkanen, J.; Voutilainen, M.; Härkönen, J.; Karimäki, V.; Kinnunen, R.; Lampén, T.; Lassila-Perini, K.; Lehti, S.; Lindén, T.; Luukka, P.; Peltola, T.; Tuominiemi, J.; Tuovinen, E.; Wendland, L.; Talvitie, J.; Tuuva, T.; Besancon, M.; Couderc, F.; Dejardin, M.; Denegri, D.; Fabbro, B.; Faure, J. L.; Favaro, C.; Ferri, F.; Ganjour, S.; Givernaud, A.; Gras, P.; Hamel de Monchenault, G.; Jarry, P.; Locci, E.; Machet, M.; Malcles, J.; Rander, J.; Rosowsky, A.; Titov, M.; Zghiche, A.; Abdulsalam, A.; Antropov, I.; Baffioni, S.; Beaudette, F.; Busson, P.; Cadamuro, L.; Chapon, E.; Charlot, C.; Davignon, O.; Filipovic, N.; Granier de Cassagnac, R.; Jo, M.; Lisniak, S.; Miné, P.; Naranjo, I. N.; Nguyen, M.; Ochando, C.; Ortona, G.; Paganini, P.; Pigard, P.; Regnard, S.; Salerno, R.; Sirois, Y.; Strebler, T.; Yilmaz, Y.; Zabi, A.; Agram, J.-L.; Andrea, J.; Aubin, A.; Bloch, D.; Brom, J.-M.; Buttignol, M.; Chabert, E. C.; Chanon, N.; Collard, C.; Conte, E.; Coubez, X.; Fontaine, J.-C.; Gelé, D.; Goerlach, U.; Goetzmann, C.; Le Bihan, A.-C.; Merlin, J. A.; Skovpen, K.; van Hove, P.; Gadrat, S.; Beauceron, S.; Bernet, C.; Boudoul, G.; Bouvier, E.
2016-04-01
A search is performed for heavy Majorana neutrinos (N) decaying into a W boson and a lepton using the CMS detector at the Large Hadron Collider. A signature of two jets and either two same sign electrons or a same sign electron-muon pair is searched for using 19.7 fb-1 of data collected during 2012 in proton-proton collisions at a centre-of-mass energy of 8 TeV. The data are found to be consistent with the expected standard model (SM) background and, in the context of a Type-1 seesaw mechanism, upper limits are set on the cross section times branching fraction for production of heavy Majorana neutrinos in the mass range between 40 and 500 GeV. The results are additionally interpreted as limits on the mixing between the heavy Majorana neutrinos and the SM neutrinos. In the mass range considered, the upper limits range between 0.00015-0.72 for |VeN|2 and 6.6 × 10-5-0.47 for | V eN V μN ∗ |2/(| V eN|2 + | V μN|2), where VℓN is the mixing element describing the mixing of the heavy neutrino with the SM neutrino of flavour ℓ. These limits are the most restrictive direct limits for heavy Majorana neutrino masses above 200 GeV. [Figure not available: see fulltext.
Dynamical Majorana edge modes in a broad class of topological mechanical systems
Prodan, Emil; Dobiszewski, Kyle; Kanwal, Alokik; Palmieri, John; Prodan, Camelia
2017-01-01
Mechanical systems can display topological characteristics similar to that of topological insulators. Here we report a large class of topological mechanical systems related to the BDI symmetry class. These are self-assembled chains of rigid bodies with an inversion centre and no reflection planes. The particle-hole symmetry characteristic to the BDI symmetry class stems from the distinct behaviour of the translational and rotational degrees of freedom under inversion. This and other generic properties led us to the remarkable conclusion that, by adjusting the gyration radius of the bodies, one can always simultaneously open a gap in the phonon spectrum, lock-in all the characteristic symmetries and generate a non-trivial topological invariant. The particle-hole symmetry occurs around a finite frequency, and hence we can witness a dynamical topological Majorana edge mode. Contrasting a floppy mode occurring at zero frequency, a dynamical edge mode can absorb and store mechanical energy, potentially opening new applications of topological mechanics. PMID:28230164
Polygon sign rules of Majorana fermions in two-dimensional topological superconductors
NASA Astrophysics Data System (ADS)
Cheng, Qiu-Bo; He, Jing; Yu, Jing; Zhao, Xiao-Ming; Kou, Su-Peng
2016-09-01
Recently, Majorana fermions (MFs) have attracted intensive attention due to their exotic statistics and possible applications in topological quantum computation. They are proposed to exist in various two-dimensional (2D) topological systems, such as px + ipy topological superconductor (SC) and nanowire-superconducting hybridization system. In this paper, we point out that Majorana fermions in different topological systems obey different types of polygon sign rules. A numerical approach is described to identify the type of polygon sign rule of the Majorana fermions. Applying the approach to study two 2D topological systems, we find that vortex-induced Majorana fermions obey topological polygon sign rule and line-defect-induced Majorana fermions obey normal polygon sign rule.
Nonlinear optomechanical detection for Majorana fermions via a hybrid nanomechanical system
2014-01-01
The pursuit for detecting the existence of Majorana fermions is a challenging task in condensed matter physics at present. In this work, we theoretically propose a novel nonlinear optical method for probing Majorana fermions in the hybrid semiconductor/superconductor heterostructure. Our proposal is based on a hybrid system constituted by a quantum dot embedded in a nanomechanical resonator. With this method, the nonlinear optical Kerr effect presents a distinct signature for the existence of Majorana fermions. Further, the vibration of the nanomechanical resonator will enhance the nonlinear optical effect, which makes the Majorana fermions more sensitive to be detected. This proposed method may provide a potential supplement for the detection of Majorana fermions. PMID:24708555
NASA Astrophysics Data System (ADS)
Ginossar, Eran; Grosfeld, Eytan
2014-09-01
Solid-state Majorana fermions are generating intensive interest because of their unique properties and possible applications in fault tolerant quantum memory devices. Here we propose a method to detect signatures of Majorana fermions in hybrid devices by employing the sensitive apparatus of the superconducting charge-qubit architecture and its efficient coupling to microwave photons. In the charge and transmon regimes of this device, we find robust signatures of the underlying Majorana fermions that are, remarkably, not washed out by the smallness of the Majorana contribution to the Josephson current. It is predicted that at special gate bias points the photon-qubit coupling can be switched off via quantum interference, and in other points it is exponentially dependent on the control parameter EJ/EC. We propose that this device could be used to manipulate the quantum state of the Majorana fermion and realize a tunable high coherence four-level system in the superconducting-circuit architecture.
Effect of interdots electronic repulsion in the Majorana signature for a double dot interferometer
NASA Astrophysics Data System (ADS)
Ricco, L. S.; Marques, Y.; Dessotti, F. A.; de Souza, M.; Seridonio, A. C.
2016-04-01
We investigate theoretically the features of the Majorana hallmark in the presence of Coulomb repulsion between two quantum dots describing a spinless double dot interferometer, where one of the dots is strongly coupled to a Kitaev wire within the topological phase. Such a system has been originally proposed without Coulomb interaction in Dessotti et al. (2014 [16]) . Our findings reveal that for dots in resonance, the ratio between the strength of Coulomb repulsion and the dot-wire coupling changes the width of the Majorana zero-bias peak for both Fano regimes studied, indicating thus that the electronic interdots correlation influences the Majorana state lifetime in the dot hybridized with the wire. Moreover, for the off-resonance case, the swap between the energy levels of the dots also modifies the width of the Majorana peak, which does not happen for the noninteracting case. The results obtained here can guide experimentalists that pursuit a way of revealing Majorana signatures.
Lepton number violation by heavy Majorana neutrino in B decays
NASA Astrophysics Data System (ADS)
Asaka, Takehiko; Ishida, Hiroyuki
2016-12-01
Heavy Majorana neutrinos are predicted in addition to ordinary active neutrinos in the models with the seesaw mechanism. We investigate the lepton number violation (LNV) in B decays induced by such a heavy neutrino N with GeV-scale mass. Especially, we consider the decay channel B+ →μ+ N →μ+μ+π- and derive the sensitivity limits on the mixing angle Θμ by the future search experiments at Belle II and in e+e- collisions at the Future Circular Collider (FCC-ee).
Cosmogenic Induced Background Estimation for the MAJORANA DEMONSTRATOR Experiment
NASA Astrophysics Data System (ADS)
White, Brandon; Majorana Collaboration
2016-09-01
Neutrino-less double beta (0 νββ) decay experiments probe for such rare events that the suppression and understanding of backgrounds are major experimental concerns. Cosmogenic induced isotopes have the potential to be a major background for such experiments. For the MAJORANA DEMONSTRATOR Experiment 76Ge isotope is used as both detector and source and pure electroformed copper is primarily used for detector housing. The isotopes 68Ge and 60Co are cosmogenically produced when the Germanium and Copper components are near Earth's surface. The decay of these isotopes can mimic events in the region of interest. The experiment is located at the 4850 foot level at the Sanford Underground Research Facility in Lead, South Dakota to suppress cosmogenic activation. In this talk I will present the calculations of cosmogenic backgrounds for the enriched 76Ge and electroformed Copper materials used in the MAJORANA DEMONSTRATOR. The activation is determined by the surface exposure time of materials. This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics, the Particle Astrophysics and Nuclear Physics Programs of the National Science Foundation, and the Sanford Underground Research Facility.
Coulomb interaction effects on the Majorana states in quantum wires.
Manolescu, A; Marinescu, D C; Stanescu, T D
2014-04-30
The stability of the Majorana modes in the presence of a repulsive interaction is studied in the standard semiconductor wire-metallic superconductor configuration. The effects of short-range Coulomb interaction, which is incorporated using a purely repulsive δ-function to model the strong screening effect due to the presence of the superconductor, are determined within a Hartree-Fock approximation of the effective Bogoliubov-De Gennes Hamiltonian that describes the low-energy physics of the wire. Through a numerical diagonalization procedure we obtain interaction corrections to the single particle eigenstates and calculate the extended topological phase diagram in terms of the chemical potential and the Zeeman energy. We find that, for a fixed Zeeman energy, the interaction shifts the phase boundaries to a higher chemical potential, whereas for a fixed chemical potential this shift can occur either at lower or higher Zeeman energies. These effects can be interpreted as a renormalization of the g-factor due to the interaction. The minimum Zeeman energy needed to realize Majorana fermions decreases with the increasing strength of the Coulomb repulsion. Furthermore, we find that in wires with multi-band occupancy this effect can be enhanced by increasing the chemical potential, i.e. by occupying higher energy bands.
Josephson junction detectors for Majorana modes and Dirac fermions
NASA Astrophysics Data System (ADS)
Maiti, M.; Kulikov, K. M.; Sengupta, K.; Shukrinov, Yu. M.
2015-12-01
We demonstrate that the current-voltage (I -V ) characteristics of resistively and capacitively shunted Josephson junctions (RCSJs) hosting localized subgap Majorana states provide a phase-sensitive method for their detection. The I -V characteristics of such RCSJs, in contrast to their resistively shunted counterparts, exhibit subharmonic odd Shapiro steps. These steps, owing to their subharmonic nature, exhibit qualitatively different properties compared to harmonic odd steps of conventional junctions. In addition, the RCSJs hosting Majorana bound states also display an additional sequence of steps in the devil's staircase structure seen in their I -V characteristics; such a sequence of steps makes their I -V characteristics qualitatively distinct from that of their conventional counterparts. A similar study for RCSJs with graphene superconducting junctions hosting Dirac-like quasiparticles reveals that the Shapiro step width in their I -V curves bears a signature of the transmission resonance phenomenon of their underlying Dirac quasiparticles; consequently, these step widths exhibit a π periodic oscillatory behavior with variation of the junction barrier potential. We discuss experiments which can test our theory.
Designer non-Abelian anyon platforms: from Majorana to Fibonacci
NASA Astrophysics Data System (ADS)
Alicea, Jason; Stern, Ady
2015-12-01
The emergence of non-Abelian anyons from large collections of interacting elementary particles is a conceptually beautiful phenomenon with important ramifications for fault-tolerant quantum computing. Over the last few decades the field has evolved from a highly theoretical subject to an active experimental area, particularly following proposals for trapping non-Abelian anyons in ‘engineered’ structures built from well-understood components. In this short overview we briefly tour the impressive progress that has taken place in the quest for the simplest type of non-Abelian anyon—defects binding Majorana zero modes—and then turn to similar strategies for pursuing more exotic excitations. Specifically, we describe how interfacing simple quantum Hall systems with conventional superconductors yields ‘parafermionic’ generalizations of Majorana modes and even Fibonacci anyons—the latter enabling fully fault tolerant universal quantum computation. We structure our treatment in a manner that unifies these topics in a coherent way. The ideas synthesized here spotlight largely uncharted experimental territory in the field of quantum Hall physics that appears ripe for discovery.
Distinguishing Dirac/Majorana sterile neutrinos at the LHC
NASA Astrophysics Data System (ADS)
Dib, Claudio O.; Kim, C. S.; Wang, Kechen; Zhang, Jue
2016-07-01
We study the purely leptonic decays of W±→e±e±μ∓ν and μ±μ±e∓ν produced at the LHC, induced by sterile neutrinos with mass mN below MW in the intermediate state. Since the final state neutrino escapes detection, one cannot tell whether this process violates lepton number, which would indicate a Majorana character for the intermediate sterile neutrino. Our study shows that when the sterile neutrino mixings with electrons and muons are different enough, one can still discriminate between the Dirac and Majorana character of this intermediate neutrino by simply counting and comparing the above decay rates. After performing collider simulations and statistical analysis, we find that at the 14 TeV LHC with an integrated luminosity of 3000 fb-1, for two benchmark scenarios mN=20 and 50 GeV, at least a 3 σ level of exclusion on the Dirac case can be achieved for disparities as mild as, e.g., |UN e|2<0.7 |UN μ|2 or |UN μ|2<0.7 |UN e|2 , provided that |UN e|2 and |UN μ|2 are both above ˜2 ×10-6.
Germanium Detector Crystal Axis Orientation for the MAJORANA Demonstrator
NASA Astrophysics Data System (ADS)
Letourneau, Hannah
2013-10-01
The MAJORANA Demonstrator, currently being constructed at Sanford Underground Research Facility in Lead, South Dakota, is an array of germanium detectors which will be used to search for neutrinoless double beta decay, which would demonstrate that neutrinos have a Majorana mass term and lepton number is not conserved. An important characteristic of semiconductor detectors is the crystal axis orientation, because the propagation of electromagnetic signals is attenuated by the location of the interaction relative to the axis of the crystal. Conventionally, a goniometer is used to position a collimated low energy gamma source in many small increments around the detector to measure the rise time at each position. However, due to physical constraints from the casing of the Demonstrator, a different method must be developed. At the University of Washington this summer, I worked with a 76 Ge point-contact detector. I found the crystal axis orientation first with Americium 241, a lower energy gamma source. Then, I used a higher energy source, Thorium 232, in conjunction with the only a few angular reference points to also calculate rise time. Also, I wrote code to process the data. The success of this method will be evaluated and discussed. NSF
The status and initial results of the MAJORANA DEMONSTRATOR
NASA Astrophysics Data System (ADS)
Zhu, Xiaoyu; MAJORANA Collaboration
2017-01-01
The MAJORANA DEMONSTRATOR is an ultra-low background experiment searching for neutrinoless double-beta decay in 76Ge at the Sanford Underground Research Facility. The search for neutrinoless double-beta decay could determine the Dirac vs Majorana nature of neutrino mass and provide insight to the matter-antimatter asymmetry in the Universe. The DEMONSTRATOR is comprised of 44.8 kg (30 kg enriched in 76Ge) of high purity Ge detectors separated into two modules. Construction and commissioning of both modules completed in Summer 2016 and both modules are now acquiring physics data. In my talk, I will discuss the initial results of the first physics run utilizing both modules focusing primarily on the studies of the background and projections to a ton-scale experiment. This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics, the Particle Astrophysics Program of the National Science Foundation, and the Sanford Underground Research Facility. We acknowledge the support of the U.S. Department of Energy through the LANL/LDRD Program.
The MAJORANA Demonstrator Low-Energy Rare Event Search
NASA Astrophysics Data System (ADS)
Wiseman, Clinton; Majorana Collaboration
2016-09-01
The extremely low backgrounds of the MAJORANA DEMONSTRATOR neutrinoless double beta decay experiment, combined with the excellent energy resolution of its high-purity germanium (HPGe) detectors, provide an opportunity for a dark matter search at low energy (<100 keV). The DEMONSTRATOR is in the final stages of construction at the 4850-ft. level of the Sanford Underground Research Facility in Lead, SD. The first detector module, consisting of 16.8 kg of HPGe enriched to 88% 76Ge and 5.7 kg of natural HPGe, took 100.6 live days of commissioning data before going blind on April 14th, 2016, and the second module is nearing completion at the time of this writing. The enriched detectors have particularly low levels of cosmogenic activation from their specialized manufacturing process. These ultra-low background designs are suited to rare event searches at low energies, including light WIMPs (<10 GeV/c2) and solar axions. In this talk an update of the MAJORANA low-energy research program will be presented. This material is based upon work supported by the U.S. DOE, Office of Science, Office of Nuclear Physics, the Particle Astrophysics and Nuclear Physics Programs of the National Science Foundation, and the Sanford Underground Research Facility.
Shot noise as a measure of the lifetime and energy splitting of Majorana bound states
Lü, Hai-Feng; Guo, Zhen; Ke, Sha-Sha; Zhang, Huai-Wu; Guo, Yong
2015-04-28
We propose a scheme to measure the lifetime and energy splitting of a pair of Majorana bound states at the ends of a superconducting nanowire by using the shot noise in a dynamical channel blockade system. A quantum dot is coupled to one end of the wire and connected with two electron reservoirs. It is found that a finite Majorana energy splitting tends to produce a super-Poissonian shot noise, while Majorana relaxation process relieves the dynamical channel blockade and suppresses the noise Fano factor. When the dot energy level locates in the middle of the gap of topological superconductor, the Fano factor is independent on Majorana lifetime and Majorana energy splitting is thus extracted. For a finite energy splitting, we could evaluate the Majorana relaxation rate from the suppression of Fano factor. Under a realistic condition, the expected resolution of Majorana energy splitting and its relaxation rate calculated from our model are about 1μeV and 0.01−1μeV, respectively.
Photon-assisted tunneling through a topological superconductor with Majorana bound states
Tang, Han-Zhao; Zhang, Ying-Tao; Liu, Jian-Jun
2015-12-15
Employing the Keldysh Nonequilibrium Green’s function method, we investigate time-dependent transport through a topological superconductor with Majorana bound states in the presence of a high frequency microwave field. It is found that Majorana bound states driven by photon-assisted tunneling can absorb(emit) photons and the resulting photon-assisted tunneling side band peaks can split the Majorana bound state that then appears at non-zero bias. This splitting breaks from the current opinion that Majorana bound states appear only at zero bias and thus provides a new experimental method for detecting Majorana bound states in the Non-zero-energy mode. We not only demonstrate that the photon-assisted tunneling side band peaks are due to Non-zero-energy Majorana bound states, but also that the height of the photon-assisted tunneling side band peaks is related to the intensity of the microwave field. It is further shown that the time-varying conductance induced by the Majorana bound states shows negative values for a certain period of time, which corresponds to a manifestation of the phase coherent time-varying behavior in mesoscopic systems.
New directions in the pursuit of Majorana fermions in solid state systems.
Alicea, Jason
2012-07-01
The 1937 theoretical discovery of Majorana fermions-whose defining property is that they are their own anti-particles-has since impacted diverse problems ranging from neutrino physics and dark matter searches to the fractional quantum Hall effect and superconductivity. Despite this long history the unambiguous observation of Majorana fermions nevertheless remains an outstanding goal. This review paper highlights recent advances in the condensed matter search for Majorana that have led many in the field to believe that this quest may soon bear fruit. We begin by introducing in some detail exotic 'topological' one- and two-dimensional superconductors that support Majorana fermions at their boundaries and at vortices. We then turn to one of the key insights that arose during the past few years; namely, that it is possible to 'engineer' such exotic superconductors in the laboratory by forming appropriate heterostructures with ordinary s-wave superconductors. Numerous proposals of this type are discussed, based on diverse materials such as topological insulators, conventional semiconductors, ferromagnetic metals and many others. The all-important question of how one experimentally detects Majorana fermions in these setups is then addressed. We focus on three classes of measurements that provide smoking-gun Majorana signatures: tunneling, Josephson effects and interferometry. Finally, we discuss the most remarkable properties of condensed matter Majorana fermions-the non-Abelian exchange statistics that they generate and their associated potential for quantum computation.
Proposal to measure the quasiparticle poisoning time of Majorana bound states
NASA Astrophysics Data System (ADS)
Colbert, Jacob R.; Lee, Patrick A.
2014-04-01
We propose a method of measuring the fermion parity lifetime of Majorana fermion modes due to quasiparticle poisoning. We model quasiparticle poisoning by coupling the Majorana modes to electron reservoirs, explicitly breaking parity conservation in the system. This poisoning broadens and shortens the resonance peak associated with Majorana modes. In a two-lead geometry, the poisoning decreases the correlation in current noise between the two leads from the maximal value characteristic of crossed Andreev reflection. The latter measurement allows for calculation of the poisoning rate even if the temperature is much higher than the resonance width.
Reprint of : Full counting statistics of Majorana interferometers
NASA Astrophysics Data System (ADS)
Strübi, Grégory; Belzig, Wolfgang; Schmidt, Thomas L.; Bruder, Christoph
2016-08-01
We study the full counting statistics of interferometers for chiral Majorana fermions with two incoming and two outgoing Dirac fermion channels. In the absence of interactions, the FCS can be obtained from the 4×4 scattering matrix S that relates the outgoing Dirac fermions to the incoming Dirac fermions. After presenting explicit expressions for the higher-order current correlations for a modified Hanbury Brown-Twiss interferometer, we note that the cumulant-generating function can be interpreted such that unit-charge transfer processes correspond to two independent half-charge transfer processes, or alternatively, to two independent electron-hole conversion processes. By a combination of analytical and numerical approaches, we verify that this factorization property holds for a general SO(4) scattering matrix, i.e. for a general interferometer geometry.
Quantum simulations of neutrino oscillations and the Majorana equation
NASA Astrophysics Data System (ADS)
Noh, Changsuk; Rodriguez-Lara, Blas; Angelakis, Dimitris
2013-03-01
Two recent works on quantum simulations of relativistic equations are presented. The first is on neutrino oscillations with trapped ions as a generalization of Dirac equation simulation in 1 spatial dimension. It is shown that with two or more ion qubits it is possible to mimic the flavour oscillations of neutrinos. The second part is on quantum simulations of the Majorana equation based on the earlier work by Casanova et al. (PRX 1, 021018). We show that by decoupling the equation, it is possible to simulate with a smaller number of qubits given that one can perform complete tomography, including the spatial degrees of freedom. We acknowledge the financial support by the National Research Foundation and Ministry of Education, Singapore.
Testing the Ge detectors for the MAJORANA DEMONSTRATOR
Xu, W.; Abgrall, N.; Aguayo, E.; ...
2015-03-24
High purity germanium (HPGe) crystals will be used for the MAJORANA DEMONSTRATOR, where they serve as both the source and the detector for neutrinoless double beta decay. It is crucial for the experiment to understand the performance of the HPGe crystals. A variety of crystal properties are being investigated, including basic properties such as energy resolution, efficiency, uniformity, capacitance, leakage current and crystal axis orientation, as well as more sophisticated properties, e.g. pulse shapes and dead layer and transition layer distributions. In this talk, we will present our measurements that characterize the HPGe crystals. We will also discuss the ourmore » simulation package for the detector characterization setup, and show that additional information can be extracted from data-simulation comparisons.« less
Majorana approach to the stochastic theory of line shapes
NASA Astrophysics Data System (ADS)
Komijani, Yashar; Coleman, Piers
2016-08-01
Motivated by recent Mössbauer experiments on strongly correlated mixed-valence systems, we revisit the Kubo-Anderson stochastic theory of spectral line shapes. Using a Majorana representation for the nuclear spin we demonstrate how to recast the classic line-shape theory in a field-theoretic and diagrammatic language. We show that the leading contribution to the self-energy can reproduce most of the observed line-shape features including splitting and line-shape narrowing, while the vertex and the self-consistency corrections can be systematically included in the calculation. This approach permits us to predict the line shape produced by an arbitrary bulk charge fluctuation spectrum providing a model-independent way to extract the local charge fluctuation spectrum of the surrounding medium. We also derive an inverse formula to extract the charge fluctuation from the measured line shape.
Search for Majorana neutrinos with the SNO+ detector at SNOLAB
NASA Astrophysics Data System (ADS)
Maio, A.; SNO+ Collaboration
2015-02-01
The SNO+ experiment is adapting the Sudbury Neutrino Observatory (SNO) detector, in order to use isotope-loaded liquid scintillator as the active medium. SNO+ has multiple scientific goals, the main one being the search for neutrinoless double beta decay, the most promising signature for the possible Majorana character of neutrinos and for the absolute neutrino mass. Measurements of neutrinos from the Sun, the Earth, Supernovae and nuclear reactors are additional goals of the experiment. The detector consists of a 12m diameter spherical vessel, filled with 780 tonnes of Tellurium-loaded liquid scintillator, and surrounded by about 9500 PMTs. It is shielded by a large volume of ultra-pure water and the underground location at SNOLAB, Canada. This talk will review the Physics goals and current status of SNO+.
Operations of Majorana Bound States in Charge-qubit Arrays
NASA Astrophysics Data System (ADS)
Mao, Ting; Wang, Zidan
2014-03-01
The experimental pursuit of Majorana bound state (MBS) in one-dimensional (1D) solid state systems has been brought into the limelight since the proposal of Kitaev's toy lattice model. Here we use the inductively coupled charge-qubit array to realize a tunable Kitaev model. With the advantages of the superconducting-qubit circuit, we can manipulate the parameters of Kitaev model and change the symmetry class to which the model Hamiltonian belongs from the class D to the class BDI. We also discuss a simple class DIII model constructed by coupling two copies of the class D charge-qubit array. Using the time reversal symmetry and a residual U(1) spin rotation symmetry of the model, we explore the possibility of implementing universal single topological qubit operations.
The MAJORANA DEMONSTRATOR Neutrinoless Double-Beta Decay Experiment
Abgrall, N.; Aguayo, Estanislao; Avignone, Frank T.; Barabash, Alexander S.; Bertrand, F.; Boswell, M.; Brudanin, V.; Busch, Matthew; Caldwell, A. S.; Chan, Yuen-Dat; Christofferson, Cabot-Ann; Combs, Dustin C.; Detwiler, Jason A.; Doe, Peter J.; Efremenko, Yuri; Egorov, Viatcheslav; Ejiri, H.; Elliott, S. R.; Esterline, James H.; Fast, James E.; Finnerty, P.; Fraenkle, Florian; Galindo-Uribarri, A.; Giovanetti, G. K.; Goett, J.; Green, M.; Gruszko, J.; Guiseppe, Vincente; Gusev, K.; Hallin, A. L.; Hazama, R.; Hegai, A.; Henning, Reyco; Hoppe, Eric W.; Howard, Stanley; Howe, M. A.; Keeter, K.; Kidd, M. F.; Knecht, A.; Kochetov, Oleg; Konovalov, S.; Kouzes, Richard T.; Laferriere, Brian D.; Leon, Jonathan D.; Leviner, L.; Loach, J. C.; Luke, P.; MacMullin, S.; Martin, R. D.; Mertens, S.; Mizouni, Leila; Nomachi, Masaharu; Orrell, John L.; O'Shaughnessy, C.; Overman, Nicole R.; Phillips, David; Poon, Alan; Pushkin, K.; Radford, D. C.; Rielage, Keith; Robertson, R. G. H.; Ronquest, M. C.; Schubert, Alexis G.; Shanks, B.; Shima, T.; Shirchenko, M.; Snavely, Kyle J.; Snyder, N.; Steele, David; Strain, J.; Suriano, Anne-Marie; Thompson, J.; Timkin, V.; Tornow, Werner; Varner, R. L.; Vasilyev, Sergey; Vetter, Kai; Vorren, Kris R.; White, Brandon R.; Wilkerson, J. F.; Williams, T.; Xu, W.; Yakushev, E.; Young, A.; Yu, Chang-Hong; Yumatov, Vladimir
2014-06-01
The MAJORANA DEMONSTRATOR will search for the neutrinoless double-beta (ββ(0ν)) decay of the isotope ^{76}Ge with a mixed array of enriched and natural germanium detectors. The observation of this rare decay would indicate that the neutrino is its own antiparticle, demonstrate that lepton number is not conserved, and provide information on the absolute mass scale of the neutrino. The DEMONSTRATOR is being assembled at the 4850-foot level of the Sanford Underground Research Facility in Lead, South Dakota. The array will be situated in a low-background environment and surrounded by passive and active shielding. Here we describe the science goals of the DEMONSTRATOR and the details of its design.
The MAJORANA DEMONSTRATOR Neutrinoless Double-Beta Decay Experiment
Abgrall, N.; Aguayo, Estanislao; Avignone, III, F. T.; Barabash, A.; Bertrand, F.; Boswell, M.; Brudanin, V.; Busch, Matthew; Caldwell, A. S.; Chan, Yuen-Dat; Christofferson, Cabot-Ann; Combs, Dustin C.; Detwiler, Jason A.; Doe, Peter J.; Efremenko, Yuri; Egorov, Viatcheslav; Ejiri, H.; Elliott, S. R.; Esterline, James H.; Fast, James E.; Finnerty, P.; Fraenkle, Florian; Galindo-Uribarri, A.; Giovanetti, G. K.; Goett, J.; Green, M.; Gruszko, J.; Guiseppe, Vincente; Gusev, K.; Hallin, A. L.; Hazama, R.; Hegai, A.; Henning, Reyco; Hoppe, Eric W.; Howard, Stanley; Howe, M. A.; Keeter, K.; Kidd, M. F.; Knecht, A.; Kochetov, Oleg; Konovalov, S.; Kouzes, Richard T.; Laferriere, Brian D.; Leon, Jonathan D.; Leviner, L.; Loach, J. C.; Luke, P.; MacMullin, S.; Martin, R. D.; Mertens, S.; Mizouni, Leila; Nomachi, Masaharu; Orrell, John L.; O'Shaughnessy, Mark D.; Overman, Nicole R.; Phillips, David; Poon, Alan; Pushkin, K.; Radford, D. C.; Rielage, Keith; Robertson, R. G. H.; Ronquest, M. C.; Schubert, Alexis G.; Shanks, B.; Shima, T.; Shirchenko, M.; Snavely, Kyle J.; Snyder, N.; Steele, David; Strain, J.; Suriano, Anne-Marie; Thompson, J.; Timkin, V.; Tornow, Werner; Varner, R. L.; Vasilyev, Sergey; Vetter, Kai; Vorren, Kris R.; White, Brandon R.; Wilkerson, J. F.; Williams, T.; Xu, W.; Yakushev, E.; Young, A.; Yu, Chang-Hong; Yumatov, Vladimir
2014-01-01
The Majorana Demonstrator will search for the neutrinoless double-beta (ββ (0ν)) decay of the isotope ^{76}Ge with a mixed array of enriched and natural germanium detectors. The observation of this rare decay would indicate that the neutrino is its own antiparticle, demonstrate that lepton number is not conserved, and provide information on the absolute mass scale of the neutrino. TheDemonstrator is being assembled at the 4850-foot level of the SanfordUnderground Research Facility in Lead, SouthDakota. The array will be situated in a low-background environment and surrounded by passive and active shielding. Here we describe the science goals of the Demonstrator and the details of its design.
Testing the Ge detectors for the MAJORANA DEMONSTRATOR
Xu, W.; Abgrall, N.; Aguayo, E.; Avignone, F. T.; Barabash, A. S.; Bertrand, F. E.; Boswell, M.; Brudanin, V.; Busch, M.; Byram, D.; Caldwell, A. S.; Chan, Y. -D.; Christofferson, C. D.; Combs, D. C.; Cuesta, C.; Detwiler, J. A.; Doe, P. J.; Efremenko, Yu.; Egorov, V.; Ejiri, H.; Elliott, S. R.; Fast, J. E.; Finnerty, P.; Fraenkle, F. M.; Galindo-Uribarri, A.; Giovanetti, G. K.; Goett, J.; Green, M. P.; Gruszko, J.; Guiseppe, V. E.; Gusev, K.; Hallin, A. L.; Hazama, R.; Hegai, A.; Henning, R.; Hoppe, E. W.; Howard, S.; Howe, M. A.; Keeter, K. J.; Kidd, M. F.; Kochetov, O.; Konovalov, S. I.; Kouzes, R. T.; LaFerriere, B. D.; Leon, J.; Leviner, L. E.; Loach, J. C.; MacMullin, J.; MacMullin, S.; Martin, R. D.; Meijer, S.; Mertens, S.; Nomachi, M.; Orrell, J. L.; O'Shaughnessy, C.; Overman, N. R.; Phillips, D. G.; Poon, A. W.P.; Pushkin, K.; Radford, D. C.; Rager, J.; Rielage, K.; Robertson, R. G.H.; Romero-Romero, E.; Ronquest, M. C.; Schubert, A. G.; Shanks, B.; Shima, T.; Shirchenko, M.; Snavely, K. J.; Snyder, N.; Suriano, A. M.; Thompson, J.; Timkin, V.; Tornow, W.; Trimble, J. E.; Varner, R. L.; Vasilyev, S.; Vetter, K.; Vorren, K.; White, B. R.; Wilkerson, J. F.; Wiseman, C.; Yakushev, E.; Young, A. R.; Yu, C. -H.; Yumatov, V.
2015-03-24
High purity germanium (HPGe) crystals will be used for the MAJORANA DEMONSTRATOR, where they serve as both the source and the detector for neutrinoless double beta decay. It is crucial for the experiment to understand the performance of the HPGe crystals. A variety of crystal properties are being investigated, including basic properties such as energy resolution, efficiency, uniformity, capacitance, leakage current and crystal axis orientation, as well as more sophisticated properties, e.g. pulse shapes and dead layer and transition layer distributions. In this talk, we will present our measurements that characterize the HPGe crystals. We will also discuss the our simulation package for the detector characterization setup, and show that additional information can be extracted from data-simulation comparisons.
Fano fingerprints of Majoranas in Kitaev dimers of superconducting adatoms
NASA Astrophysics Data System (ADS)
Dessotti, F. A.; Ricco, L. S.; Marques, Y.; Machado, R. S.; Guessi, L. H.; Figueira, M. S.; de Souza, M.; Seridonio, A. C.
2016-09-01
We investigate theoretically a Fano interferometer composed by STM and AFM tips close to a Kitaev dimer of superconducting adatoms, in which the adatom placed under the AFM tip, encloses a pair of Majorana fermions (MFs). For the binding energy Δ of the Cooper pair delocalized into the adatoms under the tips coincident with the tunneling amplitude t between them, namely Δ=t, we find that only one MF beneath the AFM tip hybridizes with the adatom coupled to the STM tips. As a result, a gate invariance feature emerges: the Fano profile of the transmittance rises as an invariant quantity depending upon the STM tips Fermi energy, due to the symmetric swap in the gate potential of the AFM tip.
Revision of the LHCb limit on Majorana neutrinos
NASA Astrophysics Data System (ADS)
Shuve, Brian; Peskin, Michael E.
2016-12-01
We revisit the recent limits from LHCb on a Majorana neutrino N in the mass range 250-5000 MeV [1 R. Aaij et al. (LHCb Collaboration), Phys. Rev. Lett. 112, 131802 (2014)., 10.1103/PhysRevLett.112.131802]. These limits are among the best currently available, and they will be improved soon by the addition of data from Run 2 of the LHC. LHCb presented a model-independent constraint on the rate of like-sign leptonic decays, and then derived a constraint on the mixing angle Vμ 4 based on a theoretical model for the B decay width to N and the N lifetime. The model used is unfortunately unsound. We revise the conclusions of the paper based on a decay model similar to the one used for the τ lepton and provide formulas useful for future analyses.
Parity-doublet representation of Majorana fermions and neutron oscillation
NASA Astrophysics Data System (ADS)
Fujikawa, Kazuo; Tureanu, Anca
2016-12-01
We present a parity-doublet theorem for the representation of the intrinsic parity of Majorana fermions, which is expected to be useful also in condensed matter physics, and it is illustrated to provide a criterion of neutron-antineutron oscillation in a Bardeen-Cooper-Schrieffer type of effective theory with Δ B =2 baryon number-violating terms. The C P violation in the present effective theory causes no direct C P -violating effects in the oscillation itself, which is demonstrated by the exact solution, although it influences the neutron electric dipole moment in the leading order of small Δ B =2 parameters. An analog of Bogoliubov transformation, which preserves P and C P , is crucial in the analysis.
Model independent explorations of Majorana neutrino mass origins
NASA Astrophysics Data System (ADS)
Jenkins, James Phearl, Jr.
The recent observation of nonzero neutrino mass is the first concrete indication of physics beyond the Standard Model. Their properties, unique among the other fermions, leads naturally to the idea of a Majorana neutrino mass term. Despite the strong theoretical prejudice toward this concept, it must be tested experimentally. This is indeed possible in the context of next generation experiments. Unfortunately, the scale of neutrino mass generation may be too large to explore directly, but useful information may still be extracted from independent experimental channels. Here I survey various model independent probes of Majorana neutrino mass origins. A brief introduction to the concepts relevant to the analysis is followed by a discussion of the physical ranges of neutrino mass and mixing parameters within the context of standard and non-standard interactions. Armed with this, I move on to systematically analyze the properties of radiatively generated neutrino masses induced by nonrenormalizable lepton number violating effective operators of mass dimensions five through eleven. By fitting these to the observed light mass scale, I extract predictions for neutrino mixing as well as neutrinoless double beta decay, rare meson/tau decays and collider phenomenology. I find that many such models are already constrained by current data and many more will be probed in the near future. I then move on demonstrate the utility of a low scale see saw mechanism via a viable 3+2+1 sterile neutrino model that satisfies all oscillation data as well as solves problems associated with supernova kicks and heavy element nucleosynthesis. From this I extract predictions for tritium and neutrinoless double beta decay searches. This is supplemented throughout by descriptions of practical limitations in addition to suggestions for future work.
Fano interference and a slight fluctuation of the Majorana hallmark
Seridonio, A. C.; Siqueira, E. C.; Dessotti, F. A.; Machado, R. S.; Yoshida, M.
2014-02-14
According to the Liu and Baranger [Phys. Rev. B 84, 201308(R) (2011)], an isolated Majorana state bound to one edge of a long enough Kitaev chain in the topological phase and connected to a quantum dot, results in a robust transmittance of 1/2 at zero-bias. In this work, we show that the removal of such a hallmark can be achieved by using a metallic surface hosting two adatoms in a scenario where there is a lack of symmetry in the Fano effect, which is feasible by coupling the Kitaev chain to one of these adatoms. Thus in order to detect this feature experimentally, one should apply the following two-stage procedure: (i) first, attached to the adatoms, one has to lock AFM tips in opposite gate voltages (symmetric detuning of the levels Δε) and measure by an STM tip, the zero-bias conductance; (ii) thereafter, the measurement of the conductance is repeated with the gates swapped. For |Δε| away from the Fermi energy and in the case of strong coupling tip-host, this approach reveals in the transmittance, a persistent dip placed at zero-bias and immune to the aforementioned permutation, but characterized by an amplitude that fluctuates slightly around 1/2. However, in the case of a tip acting as a probe, the adatom decoupled from the Kitaev chain becomes completely inert and no fluctuation is observed. Therefore, the STM tip must be considered in the same footing as the “host+adatoms” system. As a result, we have found that despite the small difference between these two Majorana dips, the zero-bias transmittance as a function of the symmetric detuning yields two distinct behaviors, in which one of them is unpredictable by the standard Fano's theory. Therefore, to access such a non trivial pattern of Fano interference, the hypothesis of the STM tip acting as a probe should be discarded.
Majorana fermions in spin-singlet nodal superconductors with coexisting non-collinear magnetic order
NASA Astrophysics Data System (ADS)
Wang, Ziqiang; Lu, Yuan-Ming
2013-03-01
Realizations of Majorana fermions in solid state materials have attracted great interests recently in connection to topological order and quantum information processing. We propose a novel way to create Majorana fermions in superconductors. We show that an incipient non-collinear magnetic order turns a spin-singlet superconductor with nodes into a topological superconductor with a stable Majorana bound state (MBS) in the vortex core or on the edge. Moreover the topologically-stable point defect of non-collinear magnetic order also hosts a zero-energy MBS. We argue that such an exotic non-Abelian phase can be realized in extended t- J models on the triangular and square lattices. Our proposal suggests a new avenue for the search of Majorana fermions in correlated electron materials where nodal superconductivity and magnetism are two common caricatures.
Traveling Majorana Solitons in a Low-Dimensional Spin-Orbit-Coupled Fermi Superfluid
NASA Astrophysics Data System (ADS)
Zou, Peng; Brand, Joachim; Liu, Xia-Ji; Hu, Hui
2016-11-01
We investigate traveling solitons of a one- or two-dimensional spin-orbit-coupled Fermi superfluid in both topologically trivial and nontrivial regimes by solving the static and time-dependent Bogoliubov-de Gennes equations. We find a critical velocity vh for traveling solitons that is much smaller than the value predicted using the Landau criterion due to spin-orbit coupling. Above vh, our time-dependent simulations in harmonic traps indicate that traveling solitons decay by radiating sound waves. In the topological phase, we predict the existence of peculiar Majorana solitons, which host two Majorana fermions and feature a phase jump of π across the soliton, irrespective of the velocity of travel. These unusual properties of Majorana solitons may open an alternative way to manipulate Majorana fermions for fault-tolerant topological quantum computations.
Non-Kondo many-body physics in a Majorana-based Kondo type system
NASA Astrophysics Data System (ADS)
van Beek, Ian J.; Braunecker, Bernd
2016-09-01
We carry out a theoretical analysis of a prototypical Majorana system, which demonstrates the existence of a Majorana-mediated many-body state and an associated intermediate low-energy fixed point. Starting from two Majorana bound states, hosted by a Coulomb-blockaded topological superconductor and each coupled to a separate lead, we derive an effective low-energy Hamiltonian, which displays a Kondo-like character. However, in contrast to the Kondo model which tends to a strong- or weak-coupling limit under renormalization, we show that this effective Hamiltonian scales to an intermediate fixed point, whose existence is contingent upon teleportation via the Majorana modes. We conclude by determining experimental signatures of this fixed point, as well as the exotic many-body state associated with it.
Traveling Majorana Solitons in a Low-Dimensional Spin-Orbit-Coupled Fermi Superfluid.
Zou, Peng; Brand, Joachim; Liu, Xia-Ji; Hu, Hui
2016-11-25
We investigate traveling solitons of a one- or two-dimensional spin-orbit-coupled Fermi superfluid in both topologically trivial and nontrivial regimes by solving the static and time-dependent Bogoliubov-de Gennes equations. We find a critical velocity v_{h} for traveling solitons that is much smaller than the value predicted using the Landau criterion due to spin-orbit coupling. Above v_{h}, our time-dependent simulations in harmonic traps indicate that traveling solitons decay by radiating sound waves. In the topological phase, we predict the existence of peculiar Majorana solitons, which host two Majorana fermions and feature a phase jump of π across the soliton, irrespective of the velocity of travel. These unusual properties of Majorana solitons may open an alternative way to manipulate Majorana fermions for fault-tolerant topological quantum computations.
NASA Astrophysics Data System (ADS)
Barański, J.; Kobiałka, A.; Domański, T.
2017-02-01
We investigate the subgap spectrum and transport properties of the quantum dot on the interface between the metallic and superconducting leads and additionally side-coupled to the edge of the topological superconducting (TS) chain, hosting the Majorana quasiparticle. Due to the chiral nature of the Majorana states only one spin component of the quantum dot electrons (say \\uparrow ) is directly affected, however the proximity induced on-dot pairing transmits its influence on the opposite spin as well. We investigate the unique interferometric patterns driven by the Majorana quasiparticle that are different for each spin component. We also address the spin-sensitive interplay with the Kondo effect manifested at the same zero-energy and we come to the conclusion that quantum interferometry can unambiguously identify the Majorana quasiparticle.
Majorana wave-function oscillations, fermion parity switches, and disorder in Kitaev chains
NASA Astrophysics Data System (ADS)
Hegde, Suraj S.; Vishveshwara, Smitha
2016-09-01
We study the decay and oscillations of Majorana fermion wave functions and ground-state (GS) fermion parity in one-dimensional topological superconducting lattice systems. Using a Majorana transfer matrix method, we find that Majorana wave-function properties are encoded in the associated Lyapunov exponent, which in turn is the sum of two independent components: a "superconducting component," which characterizes the gap induced decay, and the "normal component," which determines the oscillations and response to chemical potential configurations. The topological phase transition separating phases with and without Majorana end modes is seen to be a cancellation of these two components. We show that Majorana wave-function oscillations are completely determined by an underlying nonsuperconducting tight-binding model and are solely responsible for GS fermion parity switches in finite-sized systems. These observations enable us to analytically chart out wave-function oscillations, the resultant GS parity configuration as a function of parameter space in uniform wires, and special parity switch points where degenerate zero energy Majorana modes are restored in spite of finite size effects. For disordered wires, we find that band oscillations are completely washed out leading to a second localization length for the Majorana mode and the remnant oscillations are randomized as per Anderson localization physics in normal systems. Our transfer matrix method further allows us to (i) reproduce known results on the scaling of midgap Majorana states and demonstrate the origin of its log-normal distribution, (ii) identify contrasting behavior of disorder-dependent GS parity switches for the cases of even versus odd number of lattice sites, and (iii) chart out the GS parity configuration and associated parity switch points as a function of disorder strength.
Majorana bound states from exceptional points in non-topological superconductors
San-Jose, Pablo; Cayao, Jorge; Prada, Elsa; Aguado, Ramón
2016-01-01
Recent experimental efforts towards the detection of Majorana bound states have focused on creating the conditions for topological superconductivity. Here we demonstrate an alternative route, which achieves fully localised zero-energy Majorana bound states when a topologically trivial superconductor is strongly coupled to a helical normal region. Such a junction can be experimentally realised by e.g. proximitizing a finite section of a nanowire with spin-orbit coupling, and combining electrostatic depletion and a Zeeman field to drive the non-proximitized (normal) portion into a helical phase. Majorana zero modes emerge in such an open system without fine-tuning as a result of charge-conjugation symmetry, and can be ultimately linked to the existence of ‘exceptional points’ (EPs) in parameter space, where two quasibound Andreev levels bifurcate into two quasibound Majorana zero modes. After the EP, one of the latter becomes non-decaying as the junction approaches perfect Andreev reflection, thus resulting in a Majorana dark state (MDS) localised at the NS junction. We show that MDSs exhibit the full range of properties associated to conventional closed-system Majorana bound states (zero-energy, self-conjugation, 4π-Josephson effect and non-Abelian braiding statistics), while not requiring topological superconductivity. PMID:26865011
Adiabatic manipulations of Majorana fermions in a three-dimensional network of quantum wires
NASA Astrophysics Data System (ADS)
Halperin, Bertrand I.; Oreg, Yuval; Stern, Ady; Refael, Gil; Alicea, Jason; von Oppen, Felix
2012-04-01
It has been proposed that localized zero-energy Majorana states can be realized in a two-dimensional network of quasi-one-dimensional semiconductor wires that are proximity coupled to a bulk superconductor. The wires should have strong spin-orbit coupling with appropriate symmetry, and their electrons should be partially polarized by a strong Zeeman field. Then, if the Fermi level is in an appropriate range, the wire can be in a topological superconducting phase, with Majorana states that occur at wire ends and at Y junctions, where three topological superconductor segments may be joined. Here we generalize these ideas to consider a three-dimensional network. The positions of Majorana states can be manipulated, and their non-Abelian properties made visible, by using external gates to selectively deplete portions of the network or by physically connecting and redividing wire segments. Majorana states can also be manipulated by reorientations of the Zeeman field on a wire segment, by physically rotating the wire about almost any axis, or by evolution of the phase of the order parameter in the proximity-coupled superconductor. We show how to keep track of sign changes in the zero-energy Hilbert space during adiabatic manipulations by monitoring the evolution of each Majorana state separately, rather than keeping track of the braiding of all possible pairs. This has conceptual advantages in the case of a three-dimensional network, and may be computationally useful even in two dimensions, if large numbers of Majorana sites are involved.
Majorana bound states from exceptional points in non-topological superconductors
NASA Astrophysics Data System (ADS)
San-Jose, Pablo; Cayao, Jorge; Prada, Elsa; Aguado, Ramón
2016-02-01
Recent experimental efforts towards the detection of Majorana bound states have focused on creating the conditions for topological superconductivity. Here we demonstrate an alternative route, which achieves fully localised zero-energy Majorana bound states when a topologically trivial superconductor is strongly coupled to a helical normal region. Such a junction can be experimentally realised by e.g. proximitizing a finite section of a nanowire with spin-orbit coupling, and combining electrostatic depletion and a Zeeman field to drive the non-proximitized (normal) portion into a helical phase. Majorana zero modes emerge in such an open system without fine-tuning as a result of charge-conjugation symmetry, and can be ultimately linked to the existence of ‘exceptional points’ (EPs) in parameter space, where two quasibound Andreev levels bifurcate into two quasibound Majorana zero modes. After the EP, one of the latter becomes non-decaying as the junction approaches perfect Andreev reflection, thus resulting in a Majorana dark state (MDS) localised at the NS junction. We show that MDSs exhibit the full range of properties associated to conventional closed-system Majorana bound states (zero-energy, self-conjugation, 4π-Josephson effect and non-Abelian braiding statistics), while not requiring topological superconductivity.
NASA Astrophysics Data System (ADS)
Pekker, David; Hou, Chang-Yu; Manucharyan, Vladimir E.; Demler, Eugene
2013-09-01
We propose to use an ancilla fluxonium qubit to interact with a Majorana qubit hosted by a topological one-dimensional wire. The coupling is obtained using the Majorana qubit-controlled 4π Josephson effect to flux bias the fluxonium qubit. We demonstrate how this coupling can be used to sensitively identify topological superconductivity, to measure the state of the Majorana qubit, to construct 2-qubit operations, and to implement quantum memories with topological protection.
Khachatryan, Vardan
2016-04-27
In this study, a search is performed for heavy Majorana neutrinos (N) decaying into a W boson and a lepton using the CMS detector at the Large Hadron Collider. A signature of two jets and either two same sign electrons or a same sign electron-muon pair is searched for using 19.7 inverse femtobarns of data collected during 2012 in proton-proton collisions at a centre-of-mass energy of 8 TeV. The data are found to be consistent with the expected standard model (SM) background and, in the context of a Type-1 seesaw mechanism, upper limits are set on the cross section times branching fraction for production of heavy Majorana neutrinos in the mass range between 40 and 500 GeV. The results are additionally interpreted as limits on the mixing between the heavy Majorana neutrinos and the SM neutrinos. In the mass range considered, the upper limits range between 0.00015 - 0.72 for |V_{eN}|^{2} and 6.6x10^{-5} - 0.47 for |V_{eN} V*_{μN}|^{2} / ( |V_{eN}|^{2} + |V_{μN}|^{2}), where V_{lN} is the mixing element describing the mixing of the heavy neutrino with the SM neutrino of flavour l. These limits are the most restrictive direct limits for heavy Majorana neutrino masses above 200 GeV.
The low-energy program of the MAJORANA DEMONSTRATOR
NASA Astrophysics Data System (ADS)
Massarczyk, Ralph; MAJORANA Collaboration
2017-01-01
The MAJORANA Collaboration constructed an ultra-low background, modular high-purity Ge detector array to search for neutrinoless double-beta decay in 76Ge. Located at the 4850-ft level of the Sanford Underground Research Facility, the DEMONSTRATOR detector assembly has the goal to show that it is possible to achieve background rates necessary for future ton-scale experiments. The ultra-clean assembly in combination with low-noise p-type point contact detectors allows measurements with thresholds in the keV range. The talk will give an overview of the low-energy physics and recent achievements made since the completed DEMONSTRATOR array started data taking in mid 2016. Recent results from campaign will be presented, including new limits on bosonic dark matter interaction rates. This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics, the Particle Astrophysics Program of the National Science Foundation, and the Sanford Underground Research Facility. We acknowledge the support of the U.S. Department of Energy through the LANL/LDRD Program.
Low Background Signal Readout Electronics for the MAJORANA DEMONSTRATOR
Guinn, I.; Abgrall, N.; Arnquist, Isaac J.; Avignone, Frank T.; Baldenegro-Barrera, C. X.; Barabash, Alexander S.; Bertrand, F.; Bradley, A. W.; Brudanin, V.; Busch, Matthew; Buuck, M.; Byram, D.; Caldwell, A. S.; Chan, Yuen-Dat; Christofferson, C. D.; Cuesta, C.; Detwiler, Jason A.; Efremenko, Yuri; Ejiri, H.; Elliott, Steven R.; Galindo-Uribarri, A.; Gilliss, T.; Giovanetti, G. K.; Goett, J.; Green, M. P.; Gruszko, J.; Guiseppe, V. E.; Henning, Reyco; Hoppe, Eric W.; Howard, Stanley; Howe, M. A.; Jasinski, B. R.; Keeter, K.; Kidd, M. F.; Konovalov, S.; Kouzes, Richard T.; Laferriere, Brian D.; Leon, Jonathan D.; MacMullin, J.; Martin, R. D.; Meijer, S. J.; Mertens, S.; Orrell, John L.; O'Shaughnessy, C.; Poon, Alan; Radford, D. C.; Rager, J.; Rielage, Keith; Robertson, R. G. H.; Romero-Romero, E.; Shanks, B.; Shirchenko, M.; Snyder, N.; Suriano, Anne-Marie; Tedeschi, D.; Trimble, J. E.; Varner, R. L.; Vasilyev, Sergey; Vetter, Kai; Vorren, Kris R.; White, Brandon R.; Wilkerson, J. F.; Wiseman, C.; Xu, W.; Yakushev, E.; Yu, Chang-Hong; Yumatov, Vladimir; Zhitnikov, I.
2015-03-18
The Majorana Demonstrator (MJD)[1] is an array of p-type point contact (PPC) high purity Germanium (HPGe) detectors intended to search for neutrinoless double beta decay (0vBB decay) in 76Ge. MJD will consist of 40 kg of detectors, 30 kg of which will be isotopically enriched to 87% 76Ge. The array will consist of 14 strings of four or ve detectors placed in two separate cryostats. One of the main goals of the experiment is to demonstrate the feasibility of building a tonne-scale array of detectors to search for 0vBB decay with a much higher sensitivity. This involves acheiving backgrounds in the 4 keV region of interest (ROI) around the 2039 keV Q-value of the BB decay of less than 1 count/ROI-t-y. Because many backgrounds will not directly scale with detector mass, the specific background goal of MJD is less than 3 counts/ROI-t-y.
Readout scheme for Majorana parity states using a quantum dot
NASA Astrophysics Data System (ADS)
Hoving, Darryl; Gharavi, Kaveh; Baugh, Jonathan
We propose and numerically study a scheme for reading out the parity state of a pair of Majorana bound states using a tunnel coupled quantum dot. The dot is coupled to one end of the topological wire but isolated from any reservoir, and is capacitively coupled to a charge sensor for measurement. The combined parity of the MBS-dot system is conserved and charge transfer between MBS and dot only occurs through resonant tunnelling. Resonance is controlled by the dot potential through a local gate and by the MBS splitting due to the overlap of the MBS pair wavefunctions. The latter splitting can be controlled by changing the position of the spatially separated, uncoupled MBS via a set of keyboard gates. Our simulations show that the oscillatory nature of the MBS splitting versus separation does not prevent high-fidelity readout. Indeed, the scheme can also be applied to measure the splitting versus separation, which would yield a clear signature of the topological state. With experimentally realistic parameters we find parity readout fidelities >99% should be feasible. This work was supported by the Natural Sciences and Engineering Research Council of Canada.
Transport spectroscopy of NS nanowire junctions with Majorana fermions
NASA Astrophysics Data System (ADS)
Prada, Elsa; San-Jose, Pablo; Aguado, Ramón
2012-11-01
We investigate transport through normal-superconductor nanowire junctions in the presence of spin-orbit coupling and magnetic field. As the Zeeman field crosses the critical bulk value Bc of the topological transition, a Majorana bound state (MBS) is formed, giving rise to a sharp zero-bias anomaly (ZBA) in the tunneling differential conductance. We identify novel features beyond this picture in wires with inhomogeneous depletion, such as the appearance of two MBSs inside a long depleted region for B
Data Acquisition Visualization Development for the MAJORANA DEMONSTRATOR
NASA Astrophysics Data System (ADS)
Wendlandt, Laura; Howe, Mark; Wilkerson, John; Majorana Collaboration
2013-10-01
The MAJORANA Project is building an array of germanium detectors with very low backgrounds in order to search for neutrinoless double-beta decay, a rare process that, if detected, would give us information about neutrinos. This decay would prove that neutrinos are their own anti-particles, would show that lepton number is not conserved, and would help determine absolute neutrino mass. An object-oriented, data acquisition software program known as ORCA (Object-oriented Real-time Control and Acquisition) will be used to collect data from the array. This paper describes the implementation of computer visualizations for detector calibrations, as well as tools for more general computer modeling in ORCA. Specifically, it details software that converts a CAD file to OpenGL, which can be used in ORCA. This paper also contains information about using a barium-133 source to take measurements from various locations around the detector, to better understand how data varies with detector crystal orientation. Work made possible by National Science Foundation Award OCI-1155614.
Entanglement and Majorana edge states in the Kitaev model
NASA Astrophysics Data System (ADS)
Mandal, Saptarshi; Maiti, Moitri; Varma, Vipin Kerala
2016-07-01
We investigate the von Neumann entanglement entropy and Schmidt gap in the vortex-free ground state of the Kitaev model on the honeycomb lattice for square/rectangular and cylindrical subsystems. We find that, for both the subsystems, the free-fermionic contribution to the entanglement entropy SE exhibits signatures of the phase transitions between the gapless and gapped phases. However, within the gapless phase, we find that SE does not show an expected monotonic behavior as a function of the coupling Jz between the suitably defined one-dimensional chains for either geometry; moreover, the system generically reaches a point of minimum entanglement within the gapless phase before the entanglement saturates or increases again until the gapped phase is reached. This may be attributed to the onset of gapless modes in the bulk spectrum and the competition between the correlation functions along various bonds. In the gapped phase, on the other hand, SE always monotonically varies with Jz independent of the subregion size or shape. Finally, further confirming the Li-Haldane conjecture, we find that the Schmidt gap Δ defined from the entanglement spectrum also signals the topological transitions but only if there are corresponding zero-energy Majorana edge states that simultaneously appear or disappear across the transitions. We analytically corroborate some of our results on entanglement entropy, the Schmidt gap, and the bulk-edge correspondence using perturbation theory.
High-resolution studies of the Majorana atomic chain platform
NASA Astrophysics Data System (ADS)
Feldman, Benjamin E.; Randeria, Mallika T.; Li, Jian; Jeon, Sangjun; Xie, Yonglong; Wang, Zhijun; Drozdov, Ilya K.; Andrei Bernevig, B.; Yazdani, Ali
2016-11-01
Ordered assemblies of magnetic atoms on the surface of conventional superconductors can be used to engineer topological superconducting phases and realize Majorana fermion quasiparticles (MQPs) in a condensed matter setting. Recent experiments have shown that chains of Fe atoms on Pb generically have the required electronic characteristics to form a one-dimensional topological superconductor and have revealed spatially resolved signatures of localized MQPs at the ends of such chains. Here we report higher-resolution measurements of the same atomic chain system performed using a dilution refrigerator scanning tunnelling microscope (STM). With significantly better energy resolution than previous studies, we show that the zero-bias peak (ZBP) in Fe chains has no detectable splitting from hybridization with other states. The measurements also reveal that the ZBP exhibits a distinctive `double eye’ spatial pattern on nanometre length scales. Theoretically we show that this is a general consequence of STM measurements of MQPs with substantial spectral weight in the superconducting substrate, a conclusion further supported by measurements of Pb overlayers deposited on top of the Fe chains. Finally, we report experiments performed with superconducting tips in search of the particle-hole symmetric MQP signature expected in such measurements.
Novel Majorana mode and magnetoresistance in ferromagnetic superconducting topological insulator
NASA Astrophysics Data System (ADS)
Goudarzi, H.; Khezerlou, M.; Asgarifar, S.
2017-03-01
Among the potential applications of topological insulators, we investigate theoretically the effect of coexistence of proximity-induced ferromagnetism and superconductivity on the surface states of 3-dimensional topological insulator, where the superconducting electron-hole excitations can be significantly affected by the magnetization of ferromagnetic order. We find that, Majorana mode energy, as a verified feature of TI F/S structure, along the interface sensitively depends on the magnitude of magnetization mzfs in FS region, while its slope in perpendicular incidence presents steep and no change. Since the superconducting gap is renormalized by a factor η (mzfs) , hence Andreev reflection is more or less suppressed, and, in particular, resulting subgap tunneling conductance is more sensitive to the magnitude of magnetizations in FS and F regions. Furthermore, an interesting scenario happens at the antiparallel configuration of magnetizations mzf and mzfs resulting in magnetoresistance in N/F/FS junction, which can be controlled and decreased by tuning the magnetization magnitude in FS region.
Majorana Demonstrator Bolted Joint Mechanical and Thermal Analysis
Aguayo Navarrete, Estanislao; Reid, Douglas J.; Fast, James E.
2012-06-01
The MAJORANA DEMONSTRATOR is designed to probe for neutrinoless double-beta decay, an extremely rare process with a half-life in the order of 1026 years. The experiment uses an ultra-low background, high-purity germanium detector array. The germanium crystals are both the source and the detector in this experiment. Operating these crystals as ionizing radiation detectors requires having them under cryogenic conditions (below 90 K). A liquid nitrogen thermosyphon is used to extract the heat from the detectors. The detector channels are arranged in strings and thermally coupled to the thermosyphon through a cold plate. The cold plate is joined to the thermosyphon by a bolted joint. This circular plate is housed inside the cryostat can. This document provides a detailed study of the bolted joint that connects the cold plate and the thermosyphon. An analysis of the mechanical and thermal properties of this bolted joint is presented. The force applied to the joint is derived from the torque applied to each one of the six bolts that form the joint. The thermal conductivity of the joint is measured as a function of applied force. The required heat conductivity for a successful experiment is the combination of the thermal conductivity of the detector string and this joint. The thermal behavior of the joint is experimentally implemented and analyzed in this study.
Kondo physics from quasiparticle poisoning in Majorana devices
Plugge, S.; Tsvelik, A. M.; Zazunov, A.; ...
2016-03-24
Here, we present a theoretical analysis of quasiparticle poisoning in Coulomb-blockaded Majorana fermion systems tunnel-coupled to normal-conducting leads. Taking into account finite-energy quasiparticles, we derive the effective low-energy theory and present a renormalization group analysis. We find qualitatively new effects when a quasiparticle state with very low energy is localized near a tunnel contact. For M = 2 attached leads, such “dangerous” quasiparticle poisoning processes cause a spin S = 1/2 single-channel Kondo effect, which can be detected through a characteristic zero-bias anomaly conductance peak in all Coulomb blockade valleys. For more than two attached leads, the topological Kondo effectmore » of the unpoisoned system becomes unstable. A strong-coupling bosonization analysis indicates that at low energy the poisoned lead is effectively decoupled and hence, for M > 3, the topological Kondo fixed point re-emerges, though now it involves only M–1 leads. As a consequence, for M = 3, the low-energy fixed point becomes trivial corresponding to decoupled leads.« less
Kondo physics from quasiparticle poisoning in Majorana devices
Plugge, S.; Tsvelik, A. M.; Zazunov, A.; Eriksson, E.; Egger, R.
2016-03-24
Here, we present a theoretical analysis of quasiparticle poisoning in Coulomb-blockaded Majorana fermion systems tunnel-coupled to normal-conducting leads. Taking into account finite-energy quasiparticles, we derive the effective low-energy theory and present a renormalization group analysis. We find qualitatively new effects when a quasiparticle state with very low energy is localized near a tunnel contact. For M = 2 attached leads, such “dangerous” quasiparticle poisoning processes cause a spin S = 1/2 single-channel Kondo effect, which can be detected through a characteristic zero-bias anomaly conductance peak in all Coulomb blockade valleys. For more than two attached leads, the topological Kondo effect of the unpoisoned system becomes unstable. A strong-coupling bosonization analysis indicates that at low energy the poisoned lead is effectively decoupled and hence, for M > 3, the topological Kondo fixed point re-emerges, though now it involves only M–1 leads. As a consequence, for M = 3, the low-energy fixed point becomes trivial corresponding to decoupled leads.
Kondo physics from quasiparticle poisoning in Majorana devices
NASA Astrophysics Data System (ADS)
Plugge, S.; Zazunov, A.; Eriksson, E.; Tsvelik, A. M.; Egger, R.
2016-03-01
We present a theoretical analysis of quasiparticle poisoning in Coulomb-blockaded Majorana fermion systems tunnel-coupled to normal-conducting leads. Taking into account finite-energy quasiparticles, we derive the effective low-energy theory and present a renormalization group analysis. We find qualitatively new effects when a quasiparticle state with very low energy is localized near a tunnel contact. For M =2 attached leads, such "dangerous" quasiparticle poisoning processes cause a spin S =1 /2 single-channel Kondo effect, which can be detected through a characteristic zero-bias anomaly conductance peak in all Coulomb blockade valleys. For more than two attached leads, the topological Kondo effect of the unpoisoned system becomes unstable. A strong-coupling bosonization analysis indicates that at low energy the poisoned lead is effectively decoupled and hence, for M >3 , the topological Kondo fixed point re-emerges, though now it involves only M -1 leads. As a consequence, for M =3 , the low-energy fixed point becomes trivial corresponding to decoupled leads.
Fingerprints of Majorana Bound States in Aharonov-Bohm Geometry.
Tripathi, Krashna Mohan; Das, Sourin; Rao, Sumathi
2016-04-22
We study a ring geometry, coupled to two normal metallic leads, which has a Majorana bound state (MBS) embedded in one of its arms and is threaded by Aharonov-Bohm (AB) flux ϕ. We show that by varying the AB flux, the two leads go through resonance in an anticorrelated fashion while the resonance conductance is quantized to 2e^{2}/h. We further show that such anticorrelation is completely absent when the MBS is replaced by an Andreev bound state (ABS). Hence this anti-correlation in conductance when studied as a function of ϕ provides a unique signature of the MBS which cannot be faked by an ABS. We contrast the phase sensitivity of the MBS and ABS in terms of tunneling conductances. We argue that the relative phase between the tunneling amplitude of the electrons and holes from either lead to the level (MBS or ABS), which is constrained to 0,π for the MBS and unconstrained for the ABS, is responsible for this interesting contrast in the AB effect between the MBS and ABS.
Majorana Fermions at the End of Topological Insulator Nanoribbon
NASA Astrophysics Data System (ADS)
Liu, Xiongjun; Chen, Yuqin
Majorana zero modes can exist at the end of a 1D p-wave SC. 1D semiconductor nanowire approximated a s-wave superconductor is a famous one of those proposals. In which, strong Zeeman field is required to have a large topological region, but unfortunately suppresses superconducting pairing and makes the system more sensitive to disorder. Here we propose a Nanoribbon system made of 2D topological insulator where finite size effect due to the narrow width between two edges plays an important role. A ferromagnetic insulator and an s-wave superconductor are attached at each edge, respectively. We introduce a low energy effective model to investigate the superconducting phase diagram. And, the disorder effect is studied analytically by using the self-consistent Born approximation(SCBA). Furthermore, realistic numerically calculation is carried out with a tight-binding model. We demonstrate that, strong Zeeman field generates a large topological region, and at the same time enhances superconducting pairing and makes the system more immune to disorder.
Fingerprints of Majorana Bound States in Aharonov-Bohm Geometry
NASA Astrophysics Data System (ADS)
Tripathi, Krashna Mohan; Das, Sourin; Rao, Sumathi
2016-04-01
We study a ring geometry, coupled to two normal metallic leads, which has a Majorana bound state (MBS) embedded in one of its arms and is threaded by Aharonov-Bohm (A B ) flux ϕ . We show that by varying the A B flux, the two leads go through resonance in an anticorrelated fashion while the resonance conductance is quantized to 2 e2/h . We further show that such anticorrelation is completely absent when the MBS is replaced by an Andreev bound state (ABS). Hence this anti-correlation in conductance when studied as a function of ϕ provides a unique signature of the MBS which cannot be faked by an ABS. We contrast the phase sensitivity of the MBS and ABS in terms of tunneling conductances. We argue that the relative phase between the tunneling amplitude of the electrons and holes from either lead to the level (MBS or ABS), which is constrained to 0 ,π for the MBS and unconstrained for the ABS, is responsible for this interesting contrast in the A B effect between the MBS and ABS.
The MAJORANA DEMONSTRATOR: A Search for Neutrino less Double-beta Decay of Ge-76
Xu, W.; Abgrall, N.; Avignone, III, F. T.; Bertrand, F. E.; Efremenko, Yuri; Galindo-Uribarri, Alfredo {nmn}; Green, M. P.; Radford, D. C.; Romero-Romero, E.; White, B. R.; Wilkerson, J. F.
2015-01-01
Neutrino less double-beta (Ov beta beta) decay is a hypothesized process where in some even-even nuclei it might be possible for two neutrons to simultaneously decay into two protons and two electrons without emitting neutrinos. This is possible only if neutrinos are Majorana particles, i.e. fermions that are their own antiparticles. Neutrinos being Majorana particles would explicitly violate lepton number conservation, and might play a role in the matter-antimatter asymmetry in the universe. The observation of neutrinoless double-beta decay would also provide complementary information related to neutrino masses. The MAJORANA Collaboration is constructing the MAJORANA DEMONSTRATOR, with a total of 40-kg Germanium detectors, to search for the Ov beta beta decay of Ge-76 and to demonstrate a background rate at or below 3 counts/ (ROI.t.y) in the 4 keV region of interest (ROT) around the 2039 keV Q-value for Ge-76 Ov beta beta decay. In this paper, we discuss the physics of neutrinoless double beta decay and then focus on the MAJORANA DEMONSTRATOR, including its design and approach to achieve ultra-low backgrounds and the status of the experiment.
The MAJORANA DEMONSTRATOR: A search for neutrinoless double-beta decay of ⁷⁶Ge
Xu, W.; Abgrall, N.; Avignone, F. T.; Barabash, A. S.; Bertrand, F. E.; Brudanin, V.; Busch, M.; Buuck, M.; Byram, D.; Caldwell, A. S.; Chan, Y. -D.; Christofferson, C. D.; Cuesta, C.; Detwiler, J. A.; Efremenko, Yu; Ejiri, H.; Elliott, S. R.; Galindo-Uribarri, A.; Giovanetti, G. K.; Goett, J.; Green, M. P.; Gruszko, J.; Guinn, I.; Guiseppe, V. E.; Henning, R.; Hoppe, E. W.; Howard, S.; Howe, M. A.; Jasinski, B. R.; Keeter, K. J.; Kidd, M. F.; Konovalov, S. I.; Kouzes, R. T.; LaFerriere, B. D.; Leon, J.; MacMullin, J.; Martin, R. D.; Meijer, S. J.; Mertens, S.; Orrell, J. L.; O'Shaughnessy, C.; Overman, N. R.; Poon, A. W.P.; Radford, D. C.; Rager, J.; Rielage, K.; Robertson, R. G. H.; Romero-Romero, E.; Ronquest, M. C.; Shanks, B.; Shirchenko, M.; Snyder, N.; Suriano, A. M.; Tedeschi, D.; Trimble, J. E.; Varner, R. L.; Vasilyev, S.; Vetter, K.; Vorren, K.; White, B. R.; Wilkerson, J. F.; Wiseman, C.; Yakushev, E.; Yu, C. -H.; Yumatov, V.
2015-05-01
Neutrinoless double-beta (0νββ) decay is a hypothesized process where in some even-even nuclei it might be possible for two neutrons to simultaneously decay into two protons and two electrons without emitting neutrinos. This is possible only if neutrinos are Majorana particles, i.e. fermions that are their own antiparticles. Neutrinos being Majorana particles would explicitly violate lepton number conservation, and might play a role in the matter-antimatter asymmetry in the universe. The observation of neutrinoless double-beta decay would also provide complementary information related to neutrino masses. The Majorana Collaboration is constructing the MAJORANA DEMONSTRATOR, with a total of 40-kg Germanium detectors, to search for the 0νββ decay of ⁷⁶Ge and to demonstrate a background rate at or below 3 counts/(ROI•t•y) in the 4 keV region of interest (ROI) around the 2039 keV Q-value for ⁷⁶Ge 0νββ decay. In this paper, we discuss the physics of neutrinoless double beta decay and then focus on the MAJORANA DEMONSTRATOR, including its design and approach to achieve ultra-low backgrounds and the status of the experiment.
Description of the Majorana properties of neutral particles within pauli symmetry
Gaponov, Yu. V.
2006-04-15
A mathematical model that makes it possible to describe the Majorana properties of a system of free left-and right-handed neutral fermions belonging to the same type is constructed on the basis of transformations that include the chiral U (1) group and the Pauli SU (2) group, which mixes particle and antiparticle states. For massless particles, Pauli symmetry is exact and leads to conserved charges, a chiral and a generalized lepton one; the latter is a vector in Pauli isospace, where various directions are associated with Dirac or generalized Majorana properties. In the case of a nonzero mass, the scheme in question describes the combined Dirac-Majorana properties of particles belonging to A and B ({eta}{sub P}{sup 2} = -1) and C and D ({eta}{sub P}{sup 2} = 1) inversion classes, the condition M{sub L} = -M{sub R} being satisfied for their Majorana masses. For particles of C and D classes, the mass term in the Lagrangian and the Pauli charge can be related through the generalized-lepton-charge operator. For particles of A and B classes, these features are complementary, an alternative description of particles in terms of the lepton charge or two independent Majorana fields being possible in the Dirac case. In general, however, only representations of the latter type are realized, in which case the eigenvalues of the operator that determines the structure of the mass term in the Lagrangian serve as basic features.
New topological types of Majorana modes at ends of one-dimensional topological superconductors
NASA Astrophysics Data System (ADS)
Zhao, Yuxin; Wang, Zidan
2014-03-01
As being known, topological insulators/superconductors are completely classified into various topological types with respect to their anti-unitary symmetries and dimensions, and for a certian dimension different topological types correspond to different boundary gapless modes, which is quantitatively described as a general index theorem. Based on this and Kitaev's model in class D, we construct models for all the other types of D1 topological superconductors and analyze their topologically protected Majorana zero-modes at ends. We highlight that: 1)The two kinds of Z2 topological numbers imply distinct forms of Majorana zero-modes. 2) The two-fold degenerate ground state of the DIII model with Majorana fermions can be effectively regarded as a spin when the model is coupled to a weak external magnetic field. 3)The BDI model with Z-type unit topological number can be assigned topological charges +/- 1 to its Majorana zero-modes at two ends in agreement with the general index theorem. 4)The CII model with Z-type topological number 2 may be regarded as two copies of the BDI model with certain spin-pairing patterns, and consistently the topological charge of its Majorana zero-modes is defined in the same sense of that of the BDI model.
Extracting Majorana properties from strong bounds on neutrinoless double beta decay
NASA Astrophysics Data System (ADS)
Ge, Shao-Feng; Lindner, Manfred
2017-02-01
Assuming that neutrinos are Majorana particles, we explore what information can be inferred from future strong limits (i.e. nonobservation) for neutrinoless double beta decay. Specifically we consider the case where the mass hierarchy is normal and the different contributions to the effective mass ⟨m ⟩e e partly cancel. We discuss how this fixes the two Majorana C P phases simultaneously from the Majorana triangle and how it limits the lightest neutrino mass m1 within a narrow window. The two Majorana C P phases are in this case even better determined than in the usual case for larger ⟨m ⟩ee. We show that the uncertainty in these predictions can be significantly reduced by the complementary measurement of reactor neutrino experiments, especially the medium baseline version JUNO/RENO-50. We also estimate the necessary precision on ⟨m ⟩ee to infer nontrivial Majorana C P phases and the upper limit ⟨m ⟩ee≲1 meV sets a target for the design of future neutrinoless double beta decay experiments.
The MAJORANA DEMONSTRATOR: A search for neutrinoless double-beta decay of ⁷⁶Ge
Xu, W.; Abgrall, N.; Avignone, F. T.; ...
2015-05-01
Neutrinoless double-beta (0νββ) decay is a hypothesized process where in some even-even nuclei it might be possible for two neutrons to simultaneously decay into two protons and two electrons without emitting neutrinos. This is possible only if neutrinos are Majorana particles, i.e. fermions that are their own antiparticles. Neutrinos being Majorana particles would explicitly violate lepton number conservation, and might play a role in the matter-antimatter asymmetry in the universe. The observation of neutrinoless double-beta decay would also provide complementary information related to neutrino masses. The Majorana Collaboration is constructing the MAJORANA DEMONSTRATOR, with a total of 40-kg Germanium detectors,more » to search for the 0νββ decay of ⁷⁶Ge and to demonstrate a background rate at or below 3 counts/(ROI•t•y) in the 4 keV region of interest (ROI) around the 2039 keV Q-value for ⁷⁶Ge 0νββ decay. In this paper, we discuss the physics of neutrinoless double beta decay and then focus on the MAJORANA DEMONSTRATOR, including its design and approach to achieve ultra-low backgrounds and the status of the experiment.« less
Robustness of Majorana bound states in the short-junction limit
NASA Astrophysics Data System (ADS)
Sticlet, Doru; Nijholt, Bas; Akhmerov, Anton
2017-03-01
We study the effects of strong coupling between a superconductor and a semiconductor nanowire on the creation of the Majorana bound states, when the quasiparticle dwell time in the normal part of the nanowire is much shorter than the inverse superconducting gap. This "short-junction" limit is relevant for the recent experiments using the epitaxially grown aluminum characterized by a transparent interface with the semiconductor and a small superconducting gap. We find that the small superconducting gap does not have a strong detrimental effect on the Majorana properties. Specifically, both the critical magnetic field required for creating a topological phase and the size of the Majorana bound states are independent of the superconducting gap. The critical magnetic field scales with the wire cross section, while the relative importance of the orbital and Zeeman effects of the magnetic field is controlled by the material parameters only: g factor, effective electron mass, and the semiconductor-superconductor interface transparency.
Manipulating Majorana zero modes on atomic rings with an external magnetic field
Li, Jian; Neupert, Titus; Bernevig, B. Andrei; Yazdani, Ali
2016-01-01
Non-Abelian quasiparticles have been predicted to exist in a variety of condensed matter systems. Their defining property is that an adiabatic braid between two of them results in a non-trivial change of the quantum state of the system. The simplest non-Abelian quasiparticles—the Majorana bound states—can occur in one-dimensional electronic nano-structures proximity-coupled to a bulk superconductor. Here we propose a set-up, based on chains of magnetic adatoms on the surface of a thin-film superconductor, in which the control over an externally applied magnetic field suffices to create and manipulate Majorana bound states. We consider specifically rings of adatoms and show that they allow for the creation, annihilation, adiabatic motion and braiding of pairs of Majorana bound states by varying the magnitude and orientation of the external magnetic field. PMID:26791080
NASA Astrophysics Data System (ADS)
Park, Sunghun; Recher, Patrik
2015-12-01
A phase from an adiabatic exchange of Majorana bound states (MBS) reveals their exotic anyonic nature. For detecting this exchange phase, we propose an experimental setup consisting of a Corbino geometry Josephson junction on the surface of a topological insulator, in which two MBS at zero energy can be created and rotated. We find that if a metallic tip is weakly coupled to a point on the junction, the time-averaged differential conductance of the tip-Majorana coupling shows peaks at the tip voltages e V =±(α -2 π l )ℏ/TJ, where α =π /2 is the exchange phase of the two circulating MBS, TJ is the half rotation time of MBS, and l an integer. This result constitutes a clear experimental signature of Majorana fermion exchange.
Geometry of the effective Majorana neutrino mass in the 0νββ decay
NASA Astrophysics Data System (ADS)
Xing, Zhi-zhong; Zhou, Ye-Ling
2015-01-01
The neutrinoless double-beta (0νββ) decay is a unique process used to identify the Majorana nature of massive neutrinos, and its rate depends on the size of the effective Majorana neutrino mass
Extended Majorana zero modes in a topological superconducting-normal T-junction
NASA Astrophysics Data System (ADS)
Spånslätt, Christian; Ardonne, Eddy
2017-03-01
We investigate the sub gap properties of a three terminal Josephson T-junction composed of topologically superconducting wires connected by a normal metal region. This system naturally hosts zero energy Andreev bound states which are of self-conjugate Majorana nature and we show that they are, in contrast to ordinary Majorana zero modes, spatially extended in the normal metal region. If the T-junction respects time-reversal symmetry, we show that a zero mode is distributed only in two out of three arms in the junction and tuning the superconducting phases allows for transfer of the mode between the junction arms. We further provide tunneling conductance calculations showing that these features can be detected in experiments. Our findings suggest an experimental platform for studying the nature of spatially extended Majorana zero modes.
Masses, mixing angles and phases of general Majorana neutrino mass matrix
NASA Astrophysics Data System (ADS)
Adhikary, Biswajit; Chakraborty, Mainak; Ghosal, Ambar
2013-10-01
General Majorana neutrino mass matrix is complex symmetric and for three generations of neutrinos it contains 12 real parameters. We diagonalize this general neutrino mass matrix and express the three neutrino masses, three mixing angles, one Dirac CP phase and two Majorana phases (removing three unphysical phases) in terms of the neutrino mass matrix elements. We apply the results in the context of a neutrino mass matrix derived from a broken cyclic symmetry invoking type-I seesaw mechanism. Phenomenological study of the above mass matrix allows enough parameter space to satisfy the neutrino oscillation data with only 10% breaking of this symmetry. In this model only normal mass hierarchy is allowed. In addition, the Dirac CP phase and the Majorana phases are numerically estimated. Σ m i and | m νee | are also calculated.
Anomalous crossed Andreev reflection in a mesoscopic superconducting ring hosting Majorana fermions
NASA Astrophysics Data System (ADS)
Lee, Minchul; Khim, Heunghwan; Choi, Mahn-Soo
2014-01-01
We investigate the Majorana physics and its effect on the electron transport in the nontopological superconductor (NS)-topological superconductor (TS) double junctions of a loop geometry. We find that, depending on the ratio between the lengths of two topologically different regions and the localization lengths of the Majorana fermions formed between them, two completely different transport mechanisms are working: perfect crossed Andreev reflection (CAR) for the short NS segment and perfect normal Andreev reflection for the short TS segment. The difference is explained in terms of the topologically distinct properties of subgap states in two regions, which have not been revealed so far. The exotic dependence of the CAR process on the magnetic flux threading the loop is uncovered and can be used to detect the Majorana fermions.
Wireless majorana fermions: from magnetic tunability to braiding (Conference Presentation)
NASA Astrophysics Data System (ADS)
Fatin, Geoffrey L.; Matos-Abiague, Alex; Scharf, Benedikt; Zutic, Igor
2016-10-01
In condensed-matter systems Majorana bound states (MBSs) are emergent quasiparticles with non-Abelian statistics and particle-antiparticle symmetry. While realizing the non-Abelian braiding statistics under exchange would provide both an ultimate proof for MBS existence and the key element for fault-tolerant topological quantum computing, even theoretical schemes imply a significant complexity to implement such braiding. Frequently examined 1D superconductor/semiconductor wires provide a prototypical example of how to produce MBSs, however braiding statistics are ill-defined in 1D and complex wire networks must be used. By placing an array of magnetic tunnel junctions (MTJs) above a 2D electron gas formed in a semiconductor quantum well grown on the surface of an s-wave superconductor, we have predicted the existence of highly tunable zero-energy MBSs and have proposed a novel scheme by which MBSs could be exchanged [1]. This scheme may then be used to demonstrate the states' non-Abelian statistics through braiding. The underlying magnetic textures produced by MTJ array provides a pseudo-helical texture which allows for highly-controllable topological phase transitions. By defining a local condition for topological nontriviality which takes into account the local rotation of magnetic texture, effective wire geometries support MBS formation and permit their controlled movement in 2D by altering the shape and orientation of such wires. This scheme then overcomes the requirement for a network of physical wires in order to exchange MBSs, allowing easier manipulation of such states. [1] G. L. Fatin, A. Matos-Abiague, B. Scharf, and I. Zutic, arXiv:1510.08182, preprint.
Readout of Majorana parity states using a quantum dot
NASA Astrophysics Data System (ADS)
Gharavi, Kaveh; Hoving, Darryl; Baugh, Jonathan
2016-10-01
We theoretically examine a scheme for projectively reading out the parity state of a pair of Majorana bound states (MBSs) using a tunnel-coupled quantum dot. The dot is coupled to one end of the topological wire but isolated from any reservoir and is capacitively coupled to a charge sensor for measurement. The combined parity of the MBS-dot system is conserved, and charge transfer between the MBS and dot only occurs through resonant tunneling. Resonance is controlled by the dot potential through a local gate and by the MBS energy splitting due to the overlap of the MBS pair wave functions. The latter splitting can be tuned from zero (topologically protected regime) to a finite value by gate-driven shortening of the topological wire. Simulations show that the oscillatory nature of the MBS splitting is not a fundamental obstacle to readout but requires precise gate control of the MBS spatial position and dot potential. With experimentally realistic parameters, we find that high-fidelity parity readout is achievable given nanometer-scale spatial control of the MBS and that there is a trade-off between required precisions of temporal and spatial control. Use of the scheme to measure the MBS splitting versus separation would present a clear signature of topological order and could be used to test the robustness of this order to spatial motion, a key requirement in certain schemes for scalable topological qubits. We show how the scheme can be extended to distinguish valid parity measurements from invalid ones due to gate calibration errors.
Electrical Signal Path Study and Component Assay for the MAJORANA N-Type Segmented Contact Detector
Amman, Mark; Bergevin, Marc; Chan, Yuen-Dat; Detwiler, Jason A.; Fujikawa, Brian .; Lesko, Kevin T.; Luke, Paul N.; Prior, Gersende; Poon, Alan W.; Smith, Alan R.; Vetter, Kai; Yaver, Harold; Zimmermann, Sergio
2009-02-24
The purpose of the present electrical signal path study is to explore the various issues related to the deployment of highly-segmented low-background Ge detectors for the MAJORANA double-beta decay experiment. A significant challenge is to simultaneously satisfy competing requirements for the mechanical design, electrical readout performance, and radiopurity specifications from the MAJORANA project. Common to all rare search experiments, there is a very stringent limit on the acceptable radioactivity level of all the electronics components involved. Some of the findings are summarized in this report.
The MAJORANA experiment: an ultra-low background search for neutrinoless double-beta decay
Phillips, D.; Aguayo Navarrete, Estanislao; Avignone, Frank T.; Back, Henning O.; Barabash, Alexander S.; Bergevin, M.; Bertrand, F.; Boswell, M.; Brudanin, V.; Busch, Matthew; Chan, Yuen-Dat; Christofferson, Cabot-Ann; Collar, J. I.; Combs, Dustin C.; Cooper, R. J.; Detwiler, Jason A.; Doe, Peter J.; Efremenko, Yuri; Egorov, Viatcheslav; Ejiri, H.; Elliott, Steven R.; Esterline, James H.; Fast, James E.; Fields, N.; Finnerty, P.; Fraenkle, Florian; Gehman, Victor; Giovanetti, G. K.; Green, Matthew P.; Guiseppe, Vincente; Gusey, K.; Hallin, A. L.; Hazama, R.; Henning, Reyco; Hime, Andrew; Hoppe, Eric W.; Horton, Mark; Howard, Stanley; Howe, M. A.; Johnson, R. A.; Keeter, K.; Keller, C.; Kidd, Mary; Knecht, A.; Kochetov, Oleg; Konovalov, S.; Kouzes, Richard T.; LaFerriere, Brian D.; LaRoque, B. H.; Leon, Jonathan D.; Leviner, L.; Loach, J. C.; MacMullin, S.; Marino, Michael G.; Martin, R. D.; Mei, Dong-Ming; Merriman, Jason H.; Miller, M. L.; Mizouni, Leila; Nomachi, Masaharu; Orrell, John L.; Overman, Nicole R.; Poon, Alan; Perumpilly, Gopakumar; Prior, Gersende; Radford, D. C.; Rielage, Keith; Robertson, R. G. H.; Ronquest, M. C.; Schubert, Alexis G.; Shima, T.; Shirchenko, M.; Snavely, Kyle J.; Steele, David; Strain, J.; Thomas, K.; Timkin, V.; Tornow, W.; Vanyushin, I.; Varner, R. L.; Vetter, Kai; Vorren, Kris R.; Wilkerson, J. F.; Wolfe, B. A.; Yakushev, E.; Young, A.; Yu, Chang-Hong; Yumatov, Vladimir; Zhang, C.
2012-12-01
The observation of neutrinoless double-beta decay would resolve the Majorana nature of the neutrino and could provide information on the absolute scale of the neutrino mass. The initial phase of the Majorana Experiment, known as the Demonstrator, will house 40 kg of Ge in an ultra-low background shielded environment at the 4850' level of the Sanford Underground Laboratory in Lead, SD. The objective of the Demonstrator is to validate whether a future 1-tonne experiment can achieve a background goal of one count per tonne-year in a narrow region of interest around the 76Ge neutrinoless double-beta decay peak.
NASA Astrophysics Data System (ADS)
Kraus, Christina V.; Zoller, P.; Baranov, Mikhail A.
2013-11-01
We propose an efficient protocol for braiding Majorana fermions realized as edge states in atomic wire networks, and demonstrate its robustness against experimentally relevant errors. The braiding of two Majorana fermions located on one side of two adjacent wires requires only a few local operations on this side which can be implemented using local site addressing available in current experiments with cold atoms and molecules. Based on this protocol we provide an experimentally feasible implementation of the Deutsch-Jozsa algorithm for two qubits in a topologically protected way.
Probing Non-Abelian Statistics of Majorana Fermions in Ultracold Atomic Superfluid
Zhu Shiliang; Shao, L.-B.; Wang, Z. D.; Duan, L.-M.
2011-03-11
We propose an experiment to directly probe the non-Abelian statistics of Majorana fermions by braiding them in an s-wave superfluid of ultracold atoms. We show that different orders of braiding operations give orthogonal output states that can be distinguished through Raman spectroscopy. Realization of Majorana states in an s-wave superfluid requires strong spin-orbital coupling and a controllable Zeeman field in the perpendicular direction. We present a simple laser configuration to generate the artificial spin-orbital coupling and the required Zeeman field in the dark-state subspace.
Unpaired Majorana modes in Josephson-Junction Arrays with gapless bulk excitations
Pino, M.; Tsvelik, A.; Ioffe, L. B.
2015-11-06
In this study, the search for Majorana bound states in solid-state physics has been limited to materials that display a gap in their bulk spectrum. We show that such unpaired states appear in certain quasi-one-dimensional Josephson-junction arrays with gapless bulk excitations. The bulk modes mediate a coupling between Majorana bound states via the Ruderman-Kittel-Yosida-Kasuya mechanism. As a consequence, the lowest energy doublet acquires a finite energy difference. For a realistic set of parameters this energy splitting remains much smaller than the energy of the bulk eigenstates even for short chains of length L~10.
The MAJORANA DEMONSTRATOR: A search for neutrinoless double-beta decay of germanium-76
NASA Astrophysics Data System (ADS)
Schubert, Alexis; Majorana Collaboration
2011-04-01
Observation of neutrinoless double-beta decay (0 νββ) could determine whether the neutrino is a Majorana particle and may provide information on neutrino mass. The MAJORANA Collaboration will search for 0 νββ of 76Ge in an array of germanium detectors enriched to 86% in 76Ge. Germanium detectors are a well-understood technology and have the benefits of excellent energy resolution, a high Q-value, and the ability to act as source and detector. The p-type point contact germanium detectors chosen by the MAJORANA Collaboration provide low noise, low energy threshold, and some ability to distinguish between the signal and background events. MAJORANA is constructing the DEMONSTRATOR, which will be used to conduct research and development toward a tonne-scale Ge experiment. The DEMONSTRATOR will be installed deep underground and will contain 40 kg of Ge deployed in an ultra-low-background shielded environment. Research supported by DOE under contracts DE-AC05-00OR22725 and DE-FG02-97ER41020.
Surface Majorana fermions and bulk collective modes in superfluid 3He-B
NASA Astrophysics Data System (ADS)
Park, YeJe; Chung, Suk Bum; Maciejko, Joseph
2015-02-01
The theoretical study of topological superfluids and superconductors has so far been carried out largely as a translation of the theory of noninteracting topological insulators into the superfluid language, whereby one replaces electrons by Bogoliubov quasiparticles and single-particle band Hamiltonians by Bogoliubov-de Gennes Hamiltonians. Band insulators and superfluids are, however, fundamentally different: While the former exist in the absence of interparticle interactions, the latter are broken symmetry states that owe their very existence to such interactions. In particular, unlike the static energy gap of a band insulator, the gap in a superfluid is due to a dynamical order parameter that is subject to both thermal and quantum fluctuations. In this work, we explore the consequences of bulk quantum fluctuations of the order parameter in the B phase of superfluid 3He on the topologically protected Majorana surface states. Neglecting the high-energy amplitude modes, we find that one of the three spin-orbit Goldstone modes in 3He-B couples to the surface Majorana fermions. This coupling in turn induces an effective short-range two-body interaction between the Majorana fermions, with coupling constant inversely proportional to the strength of the nuclear dipole-dipole interaction in bulk 3He. A mean-field theory suggests that the surface Majorana fermions in 3He-B may be in the vicinity of a metastable gapped time-reversal-symmetry-breaking phase.
Josephson current through a quantum dot coupled to a Majorana zero mode
NASA Astrophysics Data System (ADS)
Tang, Han-Zhao; Zhang, Ying-Tao; Liu, Jian-Jun
2016-05-01
Employing the Green’s function method, we investigate the Josephson current through a quantum dot side coupled to a topological superconducting nanowire sustaining a pair of Majorana zero modes. It is found that the Josephson current is blocked when the quantum dot is side coupled to a superconducting nanowire in a topologically trivial phase. However, when the topological superconducting nanowire transitions from a topologically trivial to a topologically non-trivial phase, an Andreev bound state arises at the zero Fermi energy of the quantum dot due to leakage of the Majorana zero mode. Thus a Josephson current can be induced by leakage of the Majorana zero mode into the quantum dot. The Josephson current shows a plateau-like structure and a clear-cut trivial/non-trivial phase transition, as a function of a Zeeman field imposed on the system. The transition and plateau-like structure can be used to probe the existence of the Majorana zero mode. The current-phase relation has also been studied.
Chalcogenide centred gold complexes.
Gimeno, M Concepción; Laguna, Antonio
2008-09-01
Chalcogenide-centred gold complexes are an important class of compounds in which a central chalcogen is surrounded by several gold atoms or gold and other metals. They have special characteristics such as unusual geometries, electron deficiency and properties such as luminescence or non-linear optical properties. The best known species are the trinuclear [E(AuPR3)3]+, 'oxonium' type species, that have high synthetic applicability, not only in other chalcogen-centred species, but in many other organometallic derivatives. The aurophilic interactions play an important role in the stability, preference for a particular geometry and luminescence properties in this type of derivatives (critical review, 117 references).
NASA Astrophysics Data System (ADS)
Pappalardo, Gelsomina; Freudenthaler, Volker; Nicolae, Doina; Mona, Lucia; Belegante, Livio; D'Amico, Giuseppe
2016-06-01
This paper presents the newly established Lidar Calibration Centre, a distributed infrastructure in Europe, whose goal is to offer services for complete characterization and calibration of lidars and ceilometers. Mobile reference lidars, laboratories for testing and characterization of optics and electronics, facilities for inspection and debugging of instruments, as well as for training in good practices are open to users from the scientific community, operational services and private sector. The Lidar Calibration Centre offers support for trans-national access through the EC HORIZON2020 project ACTRIS-2.
Majorana vortex-bound states in three-dimensional nodal noncentrosymmetric superconductors
NASA Astrophysics Data System (ADS)
Chang, Po-Yao; Matsuura, Shunji; Schnyder, Andreas P.; Ryu, Shinsei
2014-11-01
Noncentrosymmetric superconductors (NCSs), characterized by antisymmetric spin-orbit coupling and a mixture of spin-singlet and spin-triplet pairing components, are promising candidate materials for topological superconductivity. An important hallmark of topological superconductors is the existence of protected zero-energy states at surfaces or in vortex cores. Here we investigate Majorana vortex-bound states in three-dimensional nodal and fully gapped NCSs by combining analytical solutions of Bogoliubov-de Gennes (BdG) equations in the continuum with exact diagonalization of BdG Hamiltonians. We show that depending on the crystal point-group symmetries and the topological properties of the bulk Bogoliubov-quasiparticle wave functions, different types of zero-energy Majorana modes can appear inside the vortex core. We find that for nodal NCSs with tetragonal point group C4 v the vortex states are dispersionless along the vortex line, forming one-dimensional Majorana flat bands, while for NCSs with D4 point-group symmetry the vortex modes are helical Majorana states with a linear dispersion along the vortex line. NCSs with monoclinic point group C2, on the other hand, do not exhibit any zero-energy vortex-bound states. We show that in the case of the C4 v (D4) point group the stability of these Majorana zero modes is guaranteed by a combination of reflection (π rotation), time-reversal, and particle-hole symmetry. Considering continuous deformations of the quasiparticle spectrum in the presence of vortices, we show that the flat-band vortex-bound states of C4 v point-group NCSs can be adiabatically connected to the dispersionless vortex-bound states of time-reversal symmetric Weyl superconductors. Experimental implications of our results for thermal transport and tunneling measurements are discussed.
ERIC Educational Resources Information Center
Manitoba Dept. of Education, Winnipeg.
The Winnipeg Centre Project is a field-based, work-study program that attempts to create more appropriate education for the inner-city child. Sponsored by the Planning and Research Branch of the Department of Colleges and Universities Affairs and administered by Brandon University in consultation with the Winnipeg School Division, the project is…
ERIC Educational Resources Information Center
Maguire, Molly; Gunton, Ric
2000-01-01
Maple Leaf Outdoor Centre (Ontario) has added year-round outdoor education facilities and programs to help support its summer camp for disadvantaged children. Schools, youth centers, religious groups, and athletic teams conduct their own programs, collaborate with staff, or use staff-developed programs emphasizing adventure education and personal…
Implementing Responsibility Centre Budgeting
ERIC Educational Resources Information Center
Vonasek, Joseph
2011-01-01
Recently, institutes of higher education (universities) have shown a renewed interest in organisational structures and operating methodologies that generate productivity and innovation; responsibility centre budgeting (RCB) is one such process. This paper describes the underlying principles constituting RCB, its origin and structural elements, and…
ERIC Educational Resources Information Center
Sweetnam and Godfrey, Melbourne (Australia).
The Wycheproof township in New South Wales (Australia) is the regional center for a grain farming community. The Wycheproof Education Centre was formed by the merger of a separate primary and secondary school (on one site with existing buildings), into a single governing body that is educationally structured into junior, middle, and senior…
Discovering a Discovery Centre
ERIC Educational Resources Information Center
McCullagh, John; Stewart, James; Greenwood, Julian
2007-01-01
There has recently been a growth in the popularity of "science centres" and this development provides an excellent opportunity to support the primary science curriculum. Their use is therefore well worth including within initial teacher education courses. Hence, undergraduate student teachers at Stranmillis University College Belfast may…
The Iranian Documentation Centre.
ERIC Educational Resources Information Center
Harvey, John F.
The purpose of the Iranian Documentation Centr (Irandoc) was to collect that portion of the world's literature which was pertinent to Iran's research interests, to organize that material, and to promote its use by Iranian researchers. Stated more succinctly, Irandoc's purpose was to obtain ready access to the world's scientific literature in order…
NASA Astrophysics Data System (ADS)
Li, Zi-Xiang; Jiang, Yi-Fan; Yao, Hong
2016-12-01
A fundamental open issue in physics is whether and how the fermion sign problem in quantum Monte Carlo (QMC) simulations can be solved generically. Here, we show that Majorana-time-reversal (MTR) symmetries can provide a unifying principle to solve the fermion sign problem in interacting fermionic models. By systematically classifying Majorana-bilinear operators according to the anticommuting MTR symmetries they respect, we rigorously prove that there are two and only two fundamental symmetry classes which are sign-problem-free and which we call the "Majorana class" and "Kramers class," respectively. Novel sign-problem-free models in the Majorana class include interacting topological superconductors and interacting models of charge-4 e superconductors. We believe that our MTR unifying principle could shed new light on sign-problem-free QMC simulation on strongly correlated systems and interacting topological matters.
NASA Technical Reports Server (NTRS)
Labrune, Yves; Labbe, X.; Roussel, A.; Vielcanet, P.
1994-01-01
In the context of the CNES SPOT4 program CISI is particularly responsible for the development of the SPOT4 Management Centre, part of the SPOT4 ground control system located at CNES Toulouse (France) designed to provide simultaneous control over two satellites. The main operational activities are timed to synchronize with satellite visibilities (ten usable passes per day). The automatic capability of this system is achieved through agenda services (sequence of operations as defined and planned by operator). Therefore, the SPOT4 Management Centre offers limited, efficient and secure human interventions for supervision and decision making. This paper emphasizes the main system characteristics as degree of automation, level of dependability and system parameterization.
NASA Astrophysics Data System (ADS)
Wagiman, Aliani; Haja Bava Mohidin, Hazrina; Ismail, Alice Sabrina
2016-02-01
The demand for elderly centre has increased tremendously abreast with the world demographic change as the number of senior citizens rose in the 21st century. This has become one of the most crucial problems of today's era. As the world progress into modernity, more and more people are occupied with daily work causing the senior citizens to lose the care that they actually need. This paper seeks to elucidate the best possible design of an elderly care centre with new approach in order to provide the best service for them by analysing their needs and suitable activities that could elevate their quality of life. All these findings will then be incorporated into design solutions so as to enhance the living environment for the elderly especially in Malaysian context.
NASA Astrophysics Data System (ADS)
Gong, Wei-Jiang; Gao, Zhen; Shan, Wan-Fei; Yi, Guang-Yu
2016-03-01
One Majorana doublet can be realized at each end of the time-reversal-invariant Majorana nanowires. We investigate the Josephson effect in the Majorana-doublet-presented junction modified by different inter-doublet coupling manners. It is found that when the Majorana doublets couple indirectly via a non-magnetic quantum dot, only the normal Josephson effect occurs, and the fermion parity in the system just affects the current direction and amplitude. However, one magnetic field applied on the dot can induce the fractional Josephson effect in the odd-parity case. Next if the direct and indirect couplings between the Majorana doublets coexist, no fractional Josephson effect takes place, regardless of the presence of magnetic field. Instead, there almost appears the π-period-like current in some special cases. All the results are clarified by analyzing the influence of the fermion occupation in the quantum dot on the parity conservation in the whole system. We ascertain that this work will be helpful for describing the dot-assisted Josephson effect between the Majorana doublets.
Casimir effect for parallel plates involving massless Majorana fermions at finite temperature
Cheng Hongbo
2010-08-15
We study the Casimir effect for parallel plates with massless Majorana fermions obeying the bag boundary conditions at finite temperature. The thermal influence will modify the effect. It is found that the sign of the Casimir energy remains negative if the product of the plate distance and the temperature is larger than a special value, otherwise the energy will change to positive. The Casimir energy rises with the stronger thermal influence. We show that the attractive Casimir force between two parallel plates becomes greater with increasing temperature. In the case of the piston system involving the same Majorana fermions with the same boundary conditions, the attractive force on the piston will be weaker in higher-temperature surroundings.
Physical implementation of a Majorana fermion surface code for fault-tolerant quantum computation
NASA Astrophysics Data System (ADS)
Vijay, Sagar; Fu, Liang
2016-12-01
We propose a physical realization of a commuting Hamiltonian of interacting Majorana fermions realizing Z 2 topological order, using an array of Josephson-coupled topological superconductor islands. The required multi-body interaction Hamiltonian is naturally generated by a combination of charging energy induced quantum phase-slips on the superconducting islands and electron tunneling between islands. Our setup improves on a recent proposal for implementing a Majorana fermion surface code (Vijay et al 2015 Phys. Rev. X 5 041038), a ‘hybrid’ approach to fault-tolerant quantum computation that combines (1) the engineering of a stabilizer Hamiltonian with a topologically ordered ground state with (2) projective stabilizer measurements to implement error correction and a universal set of logical gates. Our hybrid strategy has advantages over the traditional surface code architecture in error suppression and single-step stabilizer measurements, and is widely applicable to implementing stabilizer codes for quantum computation.
Current experiments in germanium 0 ν β β search -- GERDA and MAJORANA
NASA Astrophysics Data System (ADS)
von Sturm, K.
2015-01-01
There are unanswered questions regarding neutrino physics that are of great interest for the scientific community. For example the absolute masses, the mass hierarchy and the nature of neutrinos are unknown up to now. The discovery of neutrinoless double beta decay (0νββ) would prove the existence of a Majorana mass, which would be linked to the half-life of the decay, and would in addition provide an elegant solution for the small mass of the neutrinos via the seesaw mechanism. Because of an existing discovery claim of 0νββ of 76Ge and the excellent energy resolution achievable, germanium is of special interest in the search for 0νββ . In this article the state of the art of germanium 0νββ search, namely the GERDA experiment and MAJORANA demonstrator, is presented. In particular, recent results of the GERDA collaboration, which strongly disfavour the above mentioned claim, are discussed.
ac Josephson Effect in Finite-Length Nanowire Junctions with Majorana Modes
NASA Astrophysics Data System (ADS)
San-Jose, Pablo; Prada, Elsa; Aguado, Ramón
2012-06-01
It has been predicted that superconducting junctions made with topological nanowires hosting Majorana bound states (MBS) exhibit an anomalous 4π-periodic Josephson effect. Finding an experimental setup with these unconventional properties poses, however, a serious challenge: for finite-length wires, the equilibrium supercurrents are always 2π periodic as anticrossings of states with the same fermionic parity are possible. We show, however, that the anomaly survives in the transient regime of the ac Josephson effect. Transients are, moreover, protected against decay by quasiparticle poisoning as a consequence of the quantum Zeno effect, which fixes the parity of Majorana qubits. The resulting long-lived ac Josephson transients may be effectively used to detect MBS.
NASA Astrophysics Data System (ADS)
Benalcazar, Wladimir A.; Teo, Jeffrey C. Y.; Hughes, Taylor L.
2014-06-01
We classify discrete-rotation symmetric topological crystalline superconductors (TCS) in two dimensions and provide the criteria for a zero-energy Majorana bound state (MBS) to be present at composite defects made from magnetic flux, dislocations, and disclinations. In addition to the Chern number that encodes chirality, discrete rotation symmetry further divides TCS into distinct stable topological classes according to the rotation eigenspectrum of Bogoliubov-de Gennes quasiparticles. Conical crystalline defects are shown to be able to accommodate robust MBS when a certain combination of these bulk topological invariants is nontrivial as dictated by the index theorems proved within. The number parity of MBS is counted by a Z2-valued index that solely depends on the disclination and the topological class of the TCS. We also discuss the implications for corner-bound Majorana modes on the boundary of topological crystalline superconductors.
Local quench, Majorana zero modes, and disturbance propagation in the Ising chain
NASA Astrophysics Data System (ADS)
Francica, G.; Apollaro, T. J. G.; Lo Gullo, N.; Plastina, F.
2016-12-01
We study the generation and propagation of local perturbations in a quantum many-body spin system. In particular, we study the Ising model in transverse field in the presence of a local field defect at one edge. This system possesses a rich phase diagram with different regions characterized by the presence of one or two Majorana zero modes. We show that their localized character (i) enables a characterization of the Ising phase transition through a local-only measurement performed on the edge spin, and (ii) strongly affects the propagation of quasiparticles emitted after the sudden removal of the defect, so that the dynamics of the local magnetization show clear deviations from a ballistic behavior in the presence of the Majorana fermions.
Finite temperature Casimir effect for massless Majorana fermions in a magnetic field
Erdas, Andrea
2011-01-15
The zeta function regularization technique is used to study the finite temperature Casimir effect for a massless Majorana fermion field confined between parallel plates and satisfying bag boundary conditions. A magnetic field perpendicular to the plates is included. An expression for the zeta function is obtained, which is exact to all orders in the magnetic field strength, temperature and plate distance. The zeta function is used to calculate the Helmholtz free energy of the Majorana field and the pressure on the plates, in the case of weak magnetic field and strong magnetic field. In both cases, simple analytic expressions are obtained for the free energy and pressure which are very accurate and valid for all values of the temperature and plate distance.
Bellini, F.
2012-11-20
The study of neutrino properties is one of the fundamental challenges in particle physics nowadays. Fifty years of investigations established that neutrinos are massive but the absolute mass scale has not yet been measured. Moreover its true nature is still unknown. Is the neutrino its own antiparticle (thus violating the lepton number) as proposed by Majorana in 1937? The only way to probe the neutrino nature is through the observation of Neutrinoless Double Beta Decay (0{nu}{beta}{beta}), a very rare spontaneous nuclear transition which emits two electrons and no neutrinos. In this paper, after a brief introduction to the theoretical framework of Majorana's neutrino, a presentation of experimental challenges posed by 0{nu}{beta}{beta} search will be given as well as an overview of present status and future perpectives of experiments.
Nadj-Perge, Stevan; Drozdov, Ilya K; Li, Jian; Chen, Hua; Jeon, Sangjun; Seo, Jungpil; MacDonald, Allan H; Bernevig, B Andrei; Yazdani, Ali
2014-10-31
Majorana fermions are predicted to localize at the edge of a topological superconductor, a state of matter that can form when a ferromagnetic system is placed in proximity to a conventional superconductor with strong spin-orbit interaction. With the goal of realizing a one-dimensional topological superconductor, we have fabricated ferromagnetic iron (Fe) atomic chains on the surface of superconducting lead (Pb). Using high-resolution spectroscopic imaging techniques, we show that the onset of superconductivity, which gaps the electronic density of states in the bulk of the Fe chains, is accompanied by the appearance of zero-energy end-states. This spatially resolved signature provides strong evidence, corroborated by other observations, for the formation of a topological phase and edge-bound Majorana fermions in our atomic chains.
Real Space Renormalization of Majorana Fermions in Quantum Nano-Wire Superconductors
NASA Astrophysics Data System (ADS)
Jafari, R.; Langari, A.; Akbari, Alireza; Kim, Ki-Seok
2017-02-01
We develop the real space quantum renormalization group (QRG) approach for majorana fermions. As an example we focus on the Kitaev chain to investigate the topological quantum phase transition (TQPT) in the one-dimensional spinless p-wave superconductor. Studying the behaviour of local compressibility and ground-state fidelity, show that the TQPT is signalled by the maximum of local compressibility at the quantum critical point tuned by the chemical potential. Moreover, a sudden drop of the ground-state fidelity and the divergence of fidelity susceptibility at the topological quantum critical point are used as proper indicators for the TQPT, which signals the appearance of Majorana fermions. Finally, we present the scaling analysis of ground-state fidelity near the critical point that manifests the universal information about the TQPT, which reveals two different scaling behaviors as we approach the critical point and thermodynamic limit.
Many-terminal Majorana island: From topological to multichannel Kondo model
NASA Astrophysics Data System (ADS)
Herviou, Loïc; Le Hur, Karyn; Mora, Christophe
2016-12-01
We study Kondo screening obtained by coupling Majorana bound states, located on a topological superconducting island, to interacting electronic reservoirs. At the charge degeneracy points of the island, we formulate an exact mapping onto the spin-1 /2 multichannel Kondo effect. The coupling to Majorana fermions transforms the tunneling terms into effective fermionic bilinear contributions with a Luttinger parameter K in the leads that is effectively doubled. For strong interactions K =1 /2 , the intermediate fixed point of the standard multichannel Kondo model is exactly recovered. It evolves with K and connects to strong coupling in the noninteracting case K =1 , with maximum conductance between the leads and robustness against channel asymmetries similarly to the topological Kondo effect. For a number of leads above four, there exists a window of Luttinger parameters in which a quantum phase transition can occur between the strong coupling topological Kondo state and the partially conducting multichannel Kondo state.
Solving fermion sign problem in quantum Monte Carlo by Majorana representation
NASA Astrophysics Data System (ADS)
Yao, Hong; Li, Zi-Xiang; Jiang, Yi-Fan
2015-03-01
We discover a new quantum Monte Carlo (QMC) method to solve the fermion sign problem in interacting fermion models by employing Majorana representation of complex fermions. We call it Majorana QMC (MQMC). Especially, MQMC is fermion sign free in simulating a class of spinless fermion models on bipartite lattices at half filling and with arbitrary range of (unfrustrated) interactions. To the best of our knowledge, MQMC is the first auxiliary field QMC method to solve fermion sign problem in spinless (more generally, odd number of species) fermion models. MQMC simulations can be performed efficiently both at finite and zero temperatures. We believe that MQMC could pave a new avenue to solve fermion sign problem in more generic fermionic models. (Zi-Xiang Li, Yi-Fan Jiang, and Hong Yao, arXiv:1408.2269).
Majorana Positivity and the Fermion Sign Problem of Quantum Monte Carlo Simulations.
Wei, Z C; Wu, Congjun; Li, Yi; Zhang, Shiwei; Xiang, T
2016-06-24
The sign problem is a major obstacle in quantum Monte Carlo simulations for many-body fermion systems. We examine this problem with a new perspective based on the Majorana reflection positivity and Majorana Kramers positivity. Two sufficient conditions are proven for the absence of the fermion sign problem. Our proof provides a unified description for all the interacting lattice fermion models previously known to be free of the sign problem based on the auxiliary field quantum Monte Carlo method. It also allows us to identify a number of new sign-problem-free interacting fermion models including, but not limited to, lattice fermion models with repulsive interactions but without particle-hole symmetry, and interacting topological insulators with spin-flip terms.
Landau-Zener-Stückelberg-Majorana lasing in circuit quantum electrodynamics
NASA Astrophysics Data System (ADS)
Neilinger, P.; Shevchenko, S. N.; Bogár, J.; Rehák, M.; Oelsner, G.; Karpov, D. S.; Hübner, U.; Astafiev, O.; Grajcar, M.; Il'ichev, E.
2016-09-01
We demonstrate amplification (and attenuation) of a probe signal by a driven two-level quantum system in the Landau-Zener-Stückelberg-Majorana regime by means of an experiment, in which a superconducting qubit was strongly coupled to a microwave cavity, in a conventional arrangement of circuit quantum electrodynamics. Two different types of flux qubit, specifically a conventional Josephson junctions qubit and a phase-slip qubit, show similar results, namely, lasing at the working points where amplification takes place. The experimental data are explained by the interaction of the probe signal with Rabi-like oscillations. The latter are created by constructive interference of Landau-Zener-Stückelberg-Majorana (LZSM) transitions during the driving period of the qubit. A detailed description of the occurrence of these oscillations and a comparison of obtained data with both analytic and numerical calculations are given.
CP asymmetry in heavy Majorana neutrino decays at finite temperature: the hierarchical case
NASA Astrophysics Data System (ADS)
Biondini, S.; Brambilla, N.; Vairo, A.
2016-09-01
We consider the simplest realization of leptogenesis with one heavy Majorana neutrino species much lighter than the other ones. In this scenario, when the temperature of the early universe is smaller than the lightest Majorana neutrino mass, we compute at first order in the Standard Model couplings and, for each coupling, at leading order in the termperature the CP asymmetry in the decays of the lightest neutrino into leptons and anti-leptons. We perform the calculation using a hierarchy of two effective field theories organized as expansions in the inverse of the heavy-neutrino masses. In the ultimate effective field theory, leading thermal corrections proportional to the Higgs self coupling and the gauge couplings are encoded in one single operator of dimension five, whereas corrections proportional to the top Yukawa coupling are encoded in four operators of dimension seven, which we compute.
Are massive Majorana neutrinos canceling each other in neutrinoless double-. beta. decay
Vergados, J.D.
1983-12-01
The possibility of various massive Majorana neutrinos canceling each other in neutrinoless double-..beta.. decay is examined. It is shown that if all neutrino eigenmasses are less than 10 MeV such a cancellation persists in the hadronic medium if initially present at the elementary (gauge) level. The same is true for neutrino mass greater than 10 GeV. In all other cases, such a cancellation will require a conspiracy between particle and nuclear physics.
Front-End Electronics Characterization, Production, and QA for the Majorana Demonstrator
NASA Astrophysics Data System (ADS)
Elia, Sophia; Majorana Collaboration
2014-09-01
The Majorana Demonstrator will search for the neutrinoless double beta decay ββ (0 ν) of the isotope 76Ge. In anticipation of the future tonne-scale experiments, its goal is to demonstrate a path forward to a background rate of one cnt/(ROI-t-y) in a 4 keV region around the Q-value of the 76Ge ββ (0 ν) . Such a background requirement significantly constrains the design of the front end electronics. Low background and low noise qualifications are a necessity. This poster first presents the characterization and noise performance in single and multi detector systems of the front end electronics developed for Majorana. The poster next reviews the full production process and finally describes the Quality Assurance tests developed for the electronics before installation in the experiment. The Majorana Demonstrator will search for the neutrinoless double beta decay ββ (0 ν) of the isotope 76Ge. In anticipation of the future tonne-scale experiments, its goal is to demonstrate a path forward to a background rate of one cnt/(ROI-t-y) in a 4 keV region around the Q-value of the 76Ge ββ (0 ν) . Such a background requirement significantly constrains the design of the front end electronics. Low background and low noise qualifications are a necessity. This poster first presents the characterization and noise performance in single and multi detector systems of the front end electronics developed for Majorana. The poster next reviews the full production process and finally describes the Quality Assurance tests developed for the electronics before installation in the experiment. We acknowledge support from the Office of Nuclear Physics in the DOE Office of Science, the Particle and Nuclear Astrophysics Program of the National Science Foundation and the Russian Foundation for Basic Research.
Status Update of the Majorana Demonstrator Neutrinoless Double Beta Decay Experiment
Gruzko, Julieta; Rielage, Keith Robert; Xu, Wenqin; Elliott, Steven Ray; Massarczyk, Ralph; Goett, John Jerome III; Chu, Pinghan
2015-11-10
Neutrinoless double beta decay searches play a major role in determining neutrino properties, in particular the Majorana or Dirac nature of the neutrino and the absolute scale of the neutrino mass. The consequences of these searches go beyond neutrino physics, with implications for Grand Unification and leptogenesis. The Majorana Collaboration is assembling a low-background array of high purity Germanium (HPGe) detectors to search for neutrinoless double-beta decay in ^{76}Ge. The Majorana Demonstrator, which is currently being constructed and commissioned at the Sanford Underground Research Facility in Lead, South Dakota, will contain 44 kg (30 kg enriched in ^{76}Ge) of HPGe detectors. Its primary goal is to demonstrate the scalability and background required for a tonne-scale Ge experiment. This is accomplished via a modular design and projected background of less than 3 cnts/tonne-yr in the region of interest. The experiment is currently taking data with the first of its enriched detectors.
Edge Majoranas on locally flat surfaces: The cone and the Möbius band
NASA Astrophysics Data System (ADS)
Quelle, A.; Smith, C. Morais; Kvorning, T.; Hansson, T. H.
2016-09-01
In this paper, we investigate the edge Majorana modes in the simplest possible p x+i py superconductor defined on surfaces with different geometries, the annulus, the cylinder, the Möbius band, and a cone (by cone we mean a cone with the tip cut away so it is topologically equivalent to the annulus and cylinder), and with different configurations of magnetic fluxes threading holes in these surfaces. In particular, we shall address two questions: Given that, in the absence of any flux, the ground state on the annulus does not support Majorana modes while the one on the cylinder does, how is it possible that the conical geometry can interpolate smoothly between the two? Given that in finite geometries edge Majorana modes have to come in pairs, how can a p x+i py state be defined on a Möbius band, which has only one edge? We show that the key to answering these questions is that the ground state depends on the geometry, even though all the surfaces are locally flat. In the case of the truncated cone, there is a nontrivial holonomy, while the nonorientable Möbius band must necessarily support a domain wall.
Parity qubits and poor man's Majorana bound states in double quantum dots
NASA Astrophysics Data System (ADS)
Leijnse, Martin; Flensberg, Karsten
2012-10-01
We study a double quantum dot connected via a common superconducting lead and show that this system can be tuned to host one Majorana bound state (MBS) on each dot. We call them “poor man's Majorana bound states” since they are not topologically protected, but otherwise share the properties of MBS formed in topological superconductors. We describe the conditions for the existence of the two spatially separated MBS, which include breaking of spin degeneracy in the two dots, with the spins polarized in different directions. Therefore, we propose to use a magnetic field configuration where the field directions on the two dots form an angle. By control of this angle the cross Andreev reflection and the tunnel amplitudes can be tuned to be approximately equal, which is a requirement for the formation of the MBS. We show that the fermionic state encoded in the two Majoranas constitutes a parity qubit, which is nonlocal and can only be measured by probing both dots simultaneously. Using a many-particle basis for the MBS, we discuss the role of interactions and show that interactions between electrons on different dots always shift the condition for degeneracy. We also show how the MBS can be probed by transport measurements and discuss how the combination of several such double dot systems allows for entanglement of parity qubits and measurement of their dephasing times.
Shot noise in a quantum dot system coupled with Majorana bound states.
Chen, Qiao; Chen, Ke-Qiu; Zhao, Hong-Kang
2014-08-06
We investigate the spectral density of shot noise and current for the system of a quantum dot coupled to Majorana bound states (MBS) employing the nonequilibrium Green's function. The Majorana bound states at the end of the wire strongly affect the shot noise. There are two types of coupling in the system: dot-MBS and MBS-MBS coupling. The curves of shot noise and current versus coupling strength have novel steps owing to the energy-level splitting caused by dot-MBS coupling. The magnitude of these steps increases with the strength of dot-MBS coupling λ but decreases with the strength of MBS-MBS coupling. The steps shift toward the large ∣eV∣ region as λ or ϵ(M) increases. In addition, dot-MBS coupling enhances the shot noise while MBS-MBS coupling suppresses the shot noise. In the absence of MBS-MBS coupling, a sharp jump emerges in the curve of the Fano factor at zero bias owing to the differential conductance being reduced by a factor of 1/2. This provides a novel technique for the detection of Majorana fermions.
Tunable transport through a quantum dot chain with side-coupled Majorana bound states
NASA Astrophysics Data System (ADS)
Jiang, Cui; Lu, Gang; Gong, Wei-Jiang
2014-09-01
We investigate the transport properties of a quantum dot (QD) chain side-coupled to a pair of Majorana bound states (MBSs). It is found that the zero-bias conductance is tightly dependent on the parity of QD number. First, if a Majorana zero mode is introduced to couple to one QD of the odd-numbered QD structure, the zero-bias conductance is equal to e/22h, but the zero-bias conductance will experience a valley-to-peak transition if the Majorana zero mode couples to the different QDs of the even-numbered QD structure. On the other hand, when the inter-MBS coupling is nonzero, the zero-bias conductance spectrum shows a peak in the odd-numbered QD structure, and in the even-numbered QD structure one conductance valley appears at the zero-bias limit. These results show the feasibility to manipulate the current in a multi-QD structure based on the QD-MBS coupling. Also, such a system can be a candidate for detecting the MBSs.
Shot noise in a quantum dot system coupled with Majorana bound states
NASA Astrophysics Data System (ADS)
Chen, Qiao; Chen, Ke-Qiu; Zhao, Hong-Kang
2014-08-01
We investigate the spectral density of shot noise and current for the system of a quantum dot coupled to Majorana bound states (MBS) employing the nonequilibrium Green’s function. The Majorana bound states at the end of the wire strongly affect the shot noise. There are two types of coupling in the system: dot-MBS and MBS-MBS coupling. The curves of shot noise and current versus coupling strength have novel steps owing to the energy-level splitting caused by dot-MBS coupling. The magnitude of these steps increases with the strength of dot-MBS coupling λ but decreases with the strength of MBS-MBS coupling. The steps shift toward the large ∣eV∣ region as λ or ɛM increases. In addition, dot-MBS coupling enhances the shot noise while MBS-MBS coupling suppresses the shot noise. In the absence of MBS-MBS coupling, a sharp jump emerges in the curve of the Fano factor at zero bias owing to the differential conductance being reduced by a factor of 1/2. This provides a novel technique for the detection of Majorana fermions.
Observation of Majorana fermions in ferromagnetic atomic chains on a superconductor
NASA Astrophysics Data System (ADS)
Nadj-Perge, Stevan
2015-03-01
Majorana fermions are zero-energy excitations predicted to localize at the edge of a topological superconductor, a state of matter that can form when a ferromagnetic system is placed in proximity to a conventional superconductor with strong spin-orbit interaction. With the goal of realizing a one-dimensional topological superconductor, we have fabricated ferromagnetic iron atomic chains on the surface of superconducting lead. Using high-resolution spectroscopic imaging techniques, we show that the onset of superconductivity, which gaps the electronic density of states in the bulk of the chains, is accompanied by the appearance of zero-energy end-states. This spatially resolved signature provides strong evidence, corroborated by other observations and theoretical modeling, for the formation of a topological phase and edge-bound Majorana states in this system. Our results demonstrates that atomic chains are viable platform for future experiments to manipulate Majorana bound states and to realize other related 1D or 2D topological superconducting phases. This work has done in collaboration with Ilya K. Drozdov, Jian Li, Hua Chen, Sangjun Jeon, Jungpil Seo, Allan H. MacDonald, B. Andrei Bernevig and Ali Yazdani. We acknowledge ONR, NSF-MRSEC, ARO-MRUI, NSF-DMR and EU Marie Curie for support.
Dantas, Andrea Dos Santos; Klein-Júnior, Luiz Carlos; Machado, Miriana S; Guecheva, Temenouga N; Dos Santos, Luciana D; Zanette, Régis A; de Mello, Fernanda B; Pêgas Henriques, João Antonio; de Mello, João Roberto Braga
2016-01-01
The present study aimed to investigate the in vitro mutagenic activity of Origanum majorana essential oil. The most abundant compounds identified by GC-MS were γ-terpinene (25.73%), α-terpinene (17.35%), terpinen-4-ol (17.24%), and sabinene (10.8%). Mutagenicity was evaluated by the Salmonella/microsome test using the preincubation procedure on TA98, TA97a, TA100, TA102, and TA1535 Salmonella typhimurium strains, in the absence or in the presence of metabolic activation. Cytotoxicity was detected at concentrations higher than 0.04 μL/plate in the absence of S9 mix and higher than 0.08 μL/plate in the presence of S9 mix and no gene mutation increase was observed. For the in vitro mammalian cell micronucleus test, V79 Chinese hamster lung fibroblasts were used. Cytotoxicity was only observed at concentrations higher than or equal to 0.05 μg/mL. Moreover, when tested in noncytotoxic concentrations, O. majorana essential oil was not able to induce chromosome mutation. The results from this study therefore suggest that O. majorana essential oil is not mutagenic at the concentrations tested in the Salmonella/microsome and micronucleus assays.
Electrical manipulation of Majorana fermions in an interdigitated superconductor-ferromagnet device.
Lee, Shu-Ping; Alicea, Jason; Refael, Gil
2012-09-21
We show that a topological phase supporting Majorana fermions can form in a two-dimensional electron gas (2DEG) adjacent to an interdigitated superconductor-ferromagnet structure. An advantage of this setup is that the 2DEG can induce the required Zeeman splitting and superconductivity from a single interface, allowing one to utilize a wide class of 2DEGs including the surface states of bulk InAs. We demonstrate that the interdigitated device supports a robust topological phase when the finger spacing λ is smaller than half of the Fermi wavelength λ(F). In this regime, the electrons effectively see a "smeared" Zeeman splitting and pairing field despite the interdigitation. The topological phase survives even in the opposite limit λ > λ(F)/2, although with a reduced bulk gap. We describe how to electrically generate a vortex in this setup to trap a Majorana mode, and predict an anomalous Fraunhofer pattern that provides a sharp signature of chiral Majorana edge states.
Klein-Júnior, Luiz Carlos; Guecheva, Temenouga N.; dos Santos, Luciana D.; Zanette, Régis A.; de Mello, Fernanda B.; de Mello, João Roberto Braga
2016-01-01
The present study aimed to investigate the in vitro mutagenic activity of Origanum majorana essential oil. The most abundant compounds identified by GC-MS were γ-terpinene (25.73%), α-terpinene (17.35%), terpinen-4-ol (17.24%), and sabinene (10.8%). Mutagenicity was evaluated by the Salmonella/microsome test using the preincubation procedure on TA98, TA97a, TA100, TA102, and TA1535 Salmonella typhimurium strains, in the absence or in the presence of metabolic activation. Cytotoxicity was detected at concentrations higher than 0.04 μL/plate in the absence of S9 mix and higher than 0.08 μL/plate in the presence of S9 mix and no gene mutation increase was observed. For the in vitro mammalian cell micronucleus test, V79 Chinese hamster lung fibroblasts were used. Cytotoxicity was only observed at concentrations higher than or equal to 0.05 μg/mL. Moreover, when tested in noncytotoxic concentrations, O. majorana essential oil was not able to induce chromosome mutation. The results from this study therefore suggest that O. majorana essential oil is not mutagenic at the concentrations tested in the Salmonella/microsome and micronucleus assays. PMID:27891531
Majorana fermion realization and relevant transport processes in a triple-quantum dot system
NASA Astrophysics Data System (ADS)
Ming-Xun, Deng; Shi-Han, Zheng; Mou, Yang; Liang-Bin, Hu; Rui-Qiang, Wang
2015-03-01
Nonequilibrium electronic transports through a system hosting three quantum dots hybridized with superconductors are investigated. By tuning the relative positions of the dot levels, we illustrate the existence of Majorana fermions and show that the Majorana feimions will either survive separately on single dots or distribute themselves among different dots with tunable probabilities. As a result, different physical mechanisms appear, including local Andreev reflection (LAR), cross Andreev reflection (CAR), and cross resonant tunneling (CRT). The resulting characteristics may be used to reveal the unique properties of Majorana fermions. In addition, we discuss the spin-polarized transports and find a pure spin current and a spin filter effect due to the joint effect of CRT and CAR, which is important for designing spintronic devices. Project supported by the New Century Excellent Talents in University of China (Grant No. NCET-10-0090), the National Natural Science Foundation of China (Grant Nos. 11474106, 11174088, and 11274124), the Program for Changjiang Scholars and Innovative Research Team in University of China (Grant No. IRT1243), and the Natural Science Foundation of Guangdong Province, China (Grant No. S2012010010681).
The Majorana Demonstrator: A search for neutrinoless double-beta decay of germanium-76
Elliott, S. R.; Boswell, M.; Goett, J.; Rielage, K.; Ronquest, M. C.; Xu, W.; Abgrall, N.; Chan, Y-D.; Hegai, A.; Martin, R. D.; Mertens, S.; Poon, A. W. P.; Aguayo, E.; Fast, J. E.; Hoppe, E. W.; Kouzes, R. T.; LaFerriere, B. D.; Orrell, J. L.; Overman, N. R.; Soin, A.; and others
2013-12-30
The MAJORANA collaboration is searching for neutrinoless double beta decay using {sup 76}Ge, which has been shown to have a number of advantages in terms of sensitivities and backgrounds. The observation of neutrinoless double-beta decay would show that lepton number is violated and that neutrinos are Majorana particles and would simultaneously provide information on neutrino mass. Attaining sensitivities for neutrino masses in the inverted hierarchy region, 15 - 50 meV, will require large, tonne-scale detectors with extremely low backgrounds, at the level of ∼1 count/t-y or lower in the region of the signal. The MAJORANA collaboration, with funding support from DOE Office of Nuclear Physics and NSF Particle Astrophysics, is constructing the DEMONSTRATOR, an array consisting of 40 kg of p-type point-contact high-purity germanium (HPGe) detectors, of which ∼30 kg will be enriched to 87% in {sup 76}Ge. The DEMONSTRATOR is being constructed in a clean room laboratory facility at the 4850' level (4300 m.w.e.) of the Sanford Underground Research Facility (SURF) in Lead, SD. It utilizes a compact graded shield approach with the inner portion consisting of ultra-clean Cu that is being electroformed and machined underground. The primary aim of the DEMONSTRATOR is to show the feasibility of a future tonne-scale measurement in terms of backgrounds and scalability.
Line nodes and surface Majorana flat bands in static and kicked p -wave superconducting Harper model
NASA Astrophysics Data System (ADS)
Wang, Huai-Qiang; Chen, M. N.; Bomantara, Raditya Weda; Gong, Jiangbin; Xing, D. Y.
2017-02-01
We investigate the effect of introducing nearest-neighbor p -wave superconducting pairing to both the static and kicked extended Harper model with two periodic phase parameters acting as artificial dimensions to simulate three-dimensional systems. It is found that in both the static model and the kicked model, by varying the p -wave pairing order parameter, the system can switch between a fully gapped phase and a gapless phase with point nodes or line nodes. The topological property of both the static and kicked model is revealed by calculating corresponding topological invariants defined in the one-dimensional lattice dimension. Under open boundary conditions along the physical dimension, Majorana flat bands at energy zero (quasienergy zero and π ) emerge in the static (kicked) model at the two-dimensional surface Brillouin zone. For certain values of pairing order parameter, (Floquet) Su-Schrieffer-Heeger-like edge modes appear in the form of arcs connecting different (Floquet) Majorana flat bands. Finally, we find that in the kicked model, it is possible to generate two controllable Floquet Majorana modes, one at quasienergy zero and the other at quasienergy π , at the same parameter values.
Majorana zero-modes and topological phases of multi-flavored Jackiw-Rebbi model
NASA Astrophysics Data System (ADS)
Ho, Shih-Hao; Lin, Feng-Li; Wen, Xiao-Gang
2012-12-01
Motivated by the recent Kitaev's K-theory analysis of topological insulators and superconductors, we adopt the same framework to study the topological phase structure of Jackiw-Rebbi model in 3+1 dimensions. According to the K-theory analysis based on the properties of the charge conjugation and time reversal symmetries, we classify the topological phases of the model. In particular, we find that there exist Z Majorana zero-modes hosted by the hedgehogs/t'Hooft-Polyakov monopoles, if the model has a T 2 = 1 time reversal symmetry. Guided by the K-theory results, we then explicitly show that a single Majorana zero mode solution exists for the SU(2) doublet fermions in some co- dimensional one planes of the mass parameter space. It turns out we can see the existence of none or a single zero mode when the fermion doublet is only two. We then take a step further to consider four-fermion case and find there can be zero, one or two normalizable zero mode in some particular choices of mass matrices. Our results also indicate that a single normalizable Majorana zero mode can be compatible with the cancellation of SU(2) Witten anomaly.
Tunable transport through a quantum dot chain with side-coupled Majorana bound states
Jiang, Cui; Lu, Gang; Gong, Wei-Jiang
2014-09-14
We investigate the transport properties of a quantum dot (QD) chain side-coupled to a pair of Majorana bound states (MBSs). It is found that the zero-bias conductance is tightly dependent on the parity of QD number. First, if a Majorana zero mode is introduced to couple to one QD of the odd-numbered QD structure, the zero-bias conductance is equal to (e{sup 2})/(2h) , but the zero-bias conductance will experience a valley-to-peak transition if the Majorana zero mode couples to the different QDs of the even-numbered QD structure. On the other hand, when the inter-MBS coupling is nonzero, the zero-bias conductance spectrum shows a peak in the odd-numbered QD structure, and in the even-numbered QD structure one conductance valley appears at the zero-bias limit. These results show the feasibility to manipulate the current in a multi-QD structure based on the QD-MBS coupling. Also, such a system can be a candidate for detecting the MBSs.
The Majorana low-noise low-background front-end electronics
Abgrall, N.; Aguayo, E.; Avignone, III, F. T.; Barabash, A. S.; Bertrand, F. E.; Boswell, M.; Brudanin, V.; Busch, M.; Byram, D.; Caldwell, A. S.; Chan, Y. -D.; Christofferson, C. D.; Combs, D. C.; Cuesta, C.; Detwiler, J. A.; Doe, P. J.; Efremenko, Yu.; Egorov, V.; Ejiri, H.; Elliott, S. R.; Fast, J. E.; Finnerty, P.; Fraenkle, F. M.; Galindo-Uribarri, A.; Giovanetti, G. K.; Goett, J.; Green, M. P.; Gruszko, J.; Guiseppe, V. E.; Gusev, K.; Hallin, A. L.; Hazama, R.; Hegai, A.; Henning, R.; Hoppe, E. W.; Howard, S.; Howe, M. A.; Keeter, K. J.; Kidd, M. F.; Kochetov, O.; Konovalov, S. I.; Kouzes, R. T.; LaFerriere, B. D.; Leon, J.; Leviner, L. E.; Loach, J. C.; MacMullin, J.; MacMullin, S.; Martin, R. D.; Meijer, S.; Mertens, S.; Nomachi, M.; Orrell, J. L.; O'Shaughnessy, C.; Overman, N. R.; Phillips, II, D. G.; Poon, A. W.P.; Pushkin, K.; Radford, D. C.; Rager, J.; Rielage, K.; Robertson, R. G.H.; Romero-Romero, E.; Ronquest, M. C.; Schubert, A. G.; Shanks, B.; Shima, T.; Shirchenko, M.; Snavely, K. J.; Snyder, N.; Suriano, A. M.; Thompson, J.; Timkin, V.; Tornow, W.; Trimble, J. E.; Varner, R. L.; Vasilyev, S.; Vetter, K.; Vorren, K.; White, B. R.; Wilkerson, J. F.; Wiseman, C.; Xu, W.; Yakushev, E.; Young, A. R.; Yu, C. -H.; Yumatov, V.
2015-03-24
The Majorana Demonstrator will search for the neutrinoless double beta decay (ββ(0ν)) of the isotope ⁷⁶Ge with a mixed array of enriched and natural germanium detectors. In view of the next generation of tonne-scale germanium-based ββ(0ν)-decay searches, a major goal of the Majorana Demonstrator is to demonstrate a path forward to achieving a background rate at or below 1 cnt/(ROI-t-y) in the 4 keV region of interest (ROI) around the 2039-keV Q-value of the ⁷⁶Ge ββ(0ν)-decay. Such a requirement on the background level significantly constrains the design of the readout electronics, which is further driven by noise and energy resolution performances. We present here the low-noise low-background front-end electronics developed for the low-capacitance p-type point contact (P-PC) germanium detectors of the Majorana Demonstrator. This resistive-feedback front-end, specifically designed to have low mass, is fabricated on a radioassayed fused-silica substrate where the feedback resistor consists of a sputtered thin film of high purity amorphous germanium and the feedback capacitor is based on the capacitance between gold conductive traces.
The Majorana low-noise low-background front-end electronics
Abgrall, N.; Aguayo, E.; Avignone, III, F. T.; ...
2015-03-24
The Majorana Demonstrator will search for the neutrinoless double beta decay (ββ(0ν)) of the isotope ⁷⁶Ge with a mixed array of enriched and natural germanium detectors. In view of the next generation of tonne-scale germanium-based ββ(0ν)-decay searches, a major goal of the Majorana Demonstrator is to demonstrate a path forward to achieving a background rate at or below 1 cnt/(ROI-t-y) in the 4 keV region of interest (ROI) around the 2039-keV Q-value of the ⁷⁶Ge ββ(0ν)-decay. Such a requirement on the background level significantly constrains the design of the readout electronics, which is further driven by noise and energy resolutionmore » performances. We present here the low-noise low-background front-end electronics developed for the low-capacitance p-type point contact (P-PC) germanium detectors of the Majorana Demonstrator. This resistive-feedback front-end, specifically designed to have low mass, is fabricated on a radioassayed fused-silica substrate where the feedback resistor consists of a sputtered thin film of high purity amorphous germanium and the feedback capacitor is based on the capacitance between gold conductive traces.« less
Effect of degenerate particles on internal bremsstrahlung of Majorana dark matter
NASA Astrophysics Data System (ADS)
Okada, Hiroshi; Toma, Takashi
2015-11-01
Gamma-rays induced by annihilation or decay of dark matter can be its smoking gun signature. In particular, gamma-rays generated by internal bremsstrahlung of Majorana and real scalar dark matter is promising since it can be a leading emission of sharp gamma-rays. However in the case of Majorana dark matter, its cross section for internal bremsstrahlung cannot be large enough to be observed by future gamma-ray experiments if the observed relic density is assumed to be thermally produced. In this paper, we introduce some degenerate particles with Majorana dark matter, and show they lead enhancement of the cross section. As a result, increase of about one order of magnitude for the cross section is possible without conflict with the observed relic density, and it would be tested by the future gamma-ray experiments such as GAMMA-400 and Cherenkov Telescope Array (CTA). In addition, the constraints of perturbativity, positron observation by the AMS experiment and direct search for dark matter are discussed.
[The primary healthcare centres].
Brambilla, Antonio; Maciocco, Gavino
2014-04-01
The central attributes of primary care are: first contact (accessibility), longitudinality (person- focused preventive and curative care overtime), patient-oriented comprehensiveness and coordination (including navigation towards secondary and tertiary care). Besides taking care of the needs of the individuals, primary health care teams are also looking at the community, especially when addressing social determinants of health. The rationale for the benefits for primary care for health has been found in: 1) greater access to needed services; 2) better quality of care; 3) a greater focus on prevention; 4) early management of health problems; 5) organizing and delivering high quality care for chronic non-communicable diseases. This paper describes the role of primary healthcare centres in strengthening community primary services and in reducing health inequalities. Furthemore, the experiences of Regional Health Services from Tuscany and Emilia-Romagna are discussed, with a brief overview of the literature.
NASA Astrophysics Data System (ADS)
Vernek, Edson; Ruiz-Tijerina, David; da Silva, Luis D.; Egues, José Carlos
2015-09-01
Quantum dot attached to topological wires has become an interesting setup to study Majorana bound state in condensed matter[1]. One of the major advantage of using a quantum dot for this purpose is that it provides a suitable manner to study the interplay between Majorana bound states and the Kondo effect. Recently we have shown that a non-interacting quantum dot side-connected to a 1D topological superconductor and to metallic normal leads can sustain a Majorana mode even when the dot is empty. This is due to the Majorana bound state of the wire leaking into the quantum dot. Now we investigate the system for the case in which the quantum dot is interacting[3]. We explore the signatures of a Majorana zero-mode leaking into the quantum dot, using a recursive Green's function approach. We then study the Kondo regime using numerical renormalization group calculations. In this regime, we show that a "0.5" contribution to the conductance appears in system due to the presence of the Majorana mode, and that it persists for a wide range of the dot parameters. In the particle-hole symmetric point, in which the Kondo effect is more robust, the total conductance reaches 3e^2/2h, clearly indicating the coexistence of a Majorana mode and the Kondo resonance in the dot. However, the Kondo effect is suppressed by a gate voltage that detunes the dot from its particle-hole symmetric point as well as by a Zeeman field. The Majorana mode, on the other hand, is almost insensitive to both of them. We show that the zero-bias conductance as a function of the magnetic field follows a well-known universal curve. This can be observed experimentally, and we propose that this universality followed by a persistent conductance of 0.5,e^2/h are evidence for the presence of Majorana-Kondo physics. This work is supported by the Brazilians agencies FAPESP, CNPq and FAPEMIG. [1] A. Y. Kitaev, Ann.Phys. {bf 303}, 2 (2003). [2] E. Vernek, P.H. Penteado, A. C. Seridonio, J. C. Egues, Phys. Rev. B {bf
NASA Astrophysics Data System (ADS)
Pedrocchi, Fabio L.; Bonesteel, N. E.; DiVincenzo, David P.
2015-09-01
The Majorana code is an example of a stabilizer code where the quantum information is stored in a system supporting well-separated Majorana bound states (MBSs). We focus on one-dimensional realizations of the Majorana code, as well as networks of such structures, and investigate their lifetime when coupled to a parity-preserving thermal environment. We apply the Davies prescription, a standard method that describes the basic aspects of a thermal environment, and derive a master equation in the Born-Markov limit. We first focus on a single wire with immobile MBSs and perform error correction to annihilate thermal excitations. In the high-temperature limit, we show both analytically and numerically that the lifetime of the Majorana qubit grows logarithmically with the size of the wire. We then study a trijunction with four MBSs when braiding is executed. We study the occurrence of dangerous error processes that prevent the lifetime of the Majorana code from growing with the size of the trijunction. The origin of the dangerous processes is the braiding itself, which separates pairs of excitations and renders the noise nonlocal; these processes arise from the basic constraints of moving MBSs in one-dimensional (1D) structures. We confirm our predictions with Monte Carlo simulations in the low-temperature regime, i.e., the regime of practical relevance. Our results put a restriction on the degree of self-correction of this particular 1D topological quantum computing architecture.
Should "Teacher Centred Teaching" Replace "Student Centred Learning"?
ERIC Educational Resources Information Center
Bailey, Patrick D.
2008-01-01
Mission statements of most HEIs across the UK support "student centred learning". In this paper, it is suggested that "teacher centred teaching" should also have a major role to play, improving the quality of the learning experience in higher education. Students are extremely diverse in their skills, weaknesses, and learning…
Odd-Even Effect of the Persistent Current in a Quantum Dot Ring with Embedded Majorana Bound States
NASA Astrophysics Data System (ADS)
Gong, Wei-Jiang; Zhao, Ying; Gao, Zhen; Yi, Guangyu; Zhang, Xin
2015-02-01
We investigate the persistent current in one mesoscopic ring formed by the couplings between the end dots of a quantum dot chain and one Majorana bound states (MBS). It is found that the persistent-current properties are dependent on the dot-number parity of the chain. When the dot number is odd, the persistent current emerges with its oscillation by tuning the magnetic flux in the ring. However, if the dot number is even, the persistent current will always be zero regardless of the presence of Majorana zero mode. By transforming the system Hamiltonian into the Majorana representation, all the results are analyzed in detail. We believe that these results provide new information for understanding the MBS-assisted electron motion property in the mesoscopic system.
Afifi, A F; Dowidar, A E
1978-01-01
Oxygen uptake by the spores of Fusarium moniliforme, F. oxysporum, F. semitectum, F. solani, Mucor racemosus and Trichoderma viride was increased in the presence of volatile substances extracted from Origanum majorana and Ocimum basilicum. This increase was greater in the presence of volatile substances from O. basilicum than O. majorana, except in the case of F. semitectum where the reverse was true. A drop in the RQ of all the germinating spores was observed in the presence of these substances. Volatile substances from O. majorana reduced the spore germination of M. racemosus whereas the spores of T. viride were stimulated to germinate. Volatile substances from O. basilicum stimulated the spore germination of M. racemosus whereas T. viride spores were not affected.
NASA Astrophysics Data System (ADS)
Marciani, M.; Schomerus, H.; Beenakker, C. W. J.
2016-08-01
We calculate the joint distribution P(S , Q) of the scattering matrix S and time-delay matrix Q = - iℏS† dS / dE of a chaotic quantum dot coupled by point contacts to metal electrodes. While S and Q are statistically independent for ballistic coupling, they become correlated for tunnel coupling. We relate the ensemble averages of Q and S and thereby obtain the average density of states at the Fermi level. We apply this to a calculation of the effect of a tunnel barrier on the Majorana resonance in a topological superconductor. We find that the presence of a Majorana bound state is hidden in the density of states and in the thermal conductance if even a single scattering channel has unit tunnel probability. The electrical conductance remains sensitive to the appearance of a Majorana bound state, and we calculate the variation of the average conductance through a topological phase transition.
Bruno, Patrick
2012-06-15
The (Berry-Aharonov-Anandan) geometric phase acquired during a cyclic quantum evolution of finite-dimensional quantum systems is studied. It is shown that a pure quantum state in a (2J+1)-dimensional Hilbert space (or, equivalently, of a spin-J system) can be mapped onto the partition function of a gas of independent Dirac strings moving on a sphere and subject to the Coulomb repulsion of 2J fixed test charges (the Majorana stars) characterizing the quantum state. The geometric phase may be viewed as the Aharonov-Bohm phase acquired by the Majorana stars as they move through the gas of Dirac strings. Expressions for the geometric connection and curvature, for the metric tensor, as well as for the multipole moments (dipole, quadrupole, etc.), are given in terms of the Majorana stars. Finally, the geometric formulation of the quantum dynamics is presented and its application to systems with exotic ordering such as spin nematics is outlined.
Chen, Hua-Jun; Zhu, Ka-Di
2015-01-01
In the present work, we theoretically propose an optical scheme to detect the possible signature of Majorana fermions via the optical pump-probe spectroscopy, which is very different from the current tunneling measurement based on electrical methods. The scheme consists of a metal nanoparticle and a semiconductor quantum dot coupled to a hybrid semiconductor/superconductor heterostructures. The results show that the probe absorption spectrum of the quantum dot presents a distinct splitting due to the existence of Majorana fermions. Owing to surface plasmon enhanced effect, this splitting will be more obvious, which makes Majorana fermions more easy to be detectable. The technique proposed here open the door for new applications ranging from robust manipulation of Majorana fermions to quantum information processing based on Majorana fermions. PMID:26310929
NASA Astrophysics Data System (ADS)
Chen, Hua-Jun; Zhu, Ka-Di
2015-08-01
In the present work, we theoretically propose an optical scheme to detect the possible signature of Majorana fermions via the optical pump-probe spectroscopy, which is very different from the current tunneling measurement based on electrical methods. The scheme consists of a metal nanoparticle and a semiconductor quantum dot coupled to a hybrid semiconductor/superconductor heterostructures. The results show that the probe absorption spectrum of the quantum dot presents a distinct splitting due to the existence of Majorana fermions. Owing to surface plasmon enhanced effect, this splitting will be more obvious, which makes Majorana fermions more easy to be detectable. The technique proposed here open the door for new applications ranging from robust manipulation of Majorana fermions to quantum information processing based on Majorana fermions.
NASA Astrophysics Data System (ADS)
Das Sarma, S.; Nag, Amit; Sau, Jay D.
2016-07-01
We consider a simple conceptual question with respect to Majorana zero modes in semiconductor nanowires: can the measured nonideal values of the zero-bias-conductance-peak in the tunneling experiments be used as a characteristic to predict the underlying topological nature of the proximity induced nanowire superconductivity? In particular, we define and calculate the topological visibility, which is a variation of the topological invariant associated with the scattering matrix of the system as well as the zero-bias-conductance-peak heights in the tunneling measurements, in the presence of dissipative broadening, using precisely the same realistic nanowire parameters to connect the topological invariants with the zero-bias tunneling conductance values. This dissipative broadening is present in both (the existing) tunneling measurements and also (any future) braiding experiments as an inevitable consequence of a finite braiding time. The connection between the topological visibility and the conductance allows us to obtain the visibility of realistic braiding experiments in nanowires, and to conclude that the current experimentally accessible systems with nonideal zero-bias conductance peaks may indeed manifest (with rather low visibility) non-Abelian statistics for the Majorana zero modes. In general, we find that a large (small) superconducting gap (Majorana peak splitting) is essential for the manifestation of the non-Abelian braiding statistics, and in particular, a zero-bias conductance value of around half the ideal quantized Majorana value should be sufficient for the manifestation of non-Abelian statistics in experimental nanowires. Our work also establishes that as a matter of principle the topological transition associated with the emergence of Majorana zero modes in finite nanowires is always a crossover (akin to a quantum phase transition at finite temperature) requiring the presence of dissipative broadening (which must be larger than the Majorana energy
Thermoelectric transport through Majorana bound states and violation of Wiedemann-Franz law
NASA Astrophysics Data System (ADS)
Ramos-Andrade, J. P.; Ávalos-Ovando, O.; Orellana, P. A.; Ulloa, S. E.
2016-10-01
We study features of thermoelectric transport through a one-dimensional topological system model hosting Majorana bound states (MBSs) at its ends. We describe the behavior of the Seebeck coefficient and the Z T figure of merit for two configurations between the MBS and normal current leads. We find an important violation of the Wiedemann-Franz law in one of these geometries, leading to sizable values of the thermoelectric efficiency over a narrow window in chemical potential away from neutrality. These findings could lead to interesting thermoelectric-based MBS detection devices, via measurements of the Seebeck coefficient and figure of merit.
Two-channel Kondo physics in a Majorana island coupled to a Josephson junction
NASA Astrophysics Data System (ADS)
Landau, L. A.; Sela, E.
2017-01-01
We study a Majorana island coupled to a bulk superconductor via a Josephson junction and to multiple external normal leads. In the absence of the Josephson coupling, the system displays a topological Kondo state, which had been largely studied recently. However, we find that this state is unstable even to small Josephson coupling, which instead leads at low temperature T to a new fixed point. Most interesting is the case of three external leads, forming a minimal electronic realization of the long sought two-channel Kondo effect. While the T =0 conductance corresponds to simple resonant Andreev reflection, the leading T dependence forms an experimental fingerprint for non-Fermi-liquid properties.
A New Infinite-Randomness Fixed Point in an Interacting Majorana Chain
NASA Astrophysics Data System (ADS)
Vijay, S.; Fu, Liang
We perform a real-space renormalization group (RG) study of an interacting chain of Majorana fermions with strong randomness. Our theory naturally describes the interacting, disordered edge of a weak topological superconductor in the BDI symmetry class of fermion topological phases. Our RG scheme reveals a new infinite-randomness fixed-point, governed by flow equations for the probability distribution of couplings. A numerical implementation of our real-space RG yields critical exponents governing susceptibilities and correlation functions near the fixed-point.
Effective response theory for zero-energy Majorana bound states in three spatial dimensions
NASA Astrophysics Data System (ADS)
Lopes, Pedro L. e. S.; Teo, Jeffrey C. Y.; Ryu, Shinsei
2015-05-01
We propose a gravitational response theory for point defects (hedgehogs) binding Majorana zero modes in (3 + 1)-dimensional superconductors. Starting in 4 + 1 dimensions, where the point defect is extended into a line, a coupling of the bulk defect texture with the gravitational field is introduced. Diffeomorphism invariance then leads to an S U (2) 2 Kac-Moody current running along the defect line. The S U (2) 2 Kac-Moody algebra accounts for the non-Abelian nature of the zero modes in 3 + 1 dimensions. It is then shown to also encode the angular momentum density which permeates throughout the bulk between hedgehog-antihedgehog pairs.
Magnetic moment of the majorana neutrino in the left-right symmetric model
Boyarkin, O. M. Boyarkina, G. G.
2013-04-15
Corrections to the neutrino magnetic dipole moment from the singly charged Higgs bosons h{sup ({+-})} and {delta}-tilde{sup (}{+-}) were calculated within the left-right symmetric model involving Majorana neutrinos. It is shown that, if the h{sup ({+-})} and {delta}-tilde{sup (}{+-}) bosons lie at the electroweak scale, the contributions from Higgs sector are commensurate with the contribution of charged gauge bosons or may even exceed it. The behavior of the neutrino flux inmatter and in amagnetic field was studied. It was found that resonance transitions between light and heavy neutrinos are forbidden.
Andreev reflection properties in a parallel mesoscopic circuit with Majorana bound states
NASA Astrophysics Data System (ADS)
Mu, Jin-Tao; Han, Yu; Gong, Wei-Jiang
2017-03-01
We investigate the Andreev reflection in a parallel mesoscopic circuit with Majorana bound states (MBSs). It is found that in such a structure, the Andreev current can be manipulated in a highly efficient way, by the adjustment of bias voltage, dot levels, inter-MBS coupling, and the applied magnetic flux. Besides, the dot-MBS coupling manner is an important factor to modulate the Andreev current, because it influences the period of the conductance oscillation. By discussing the underlying quantum interference mechanism, the Andreev-reflection property is explained in detail. We believe that all the results can assist to understand the nontrivial role of the MBSs in driving the Andreev reflection.
NASA Astrophysics Data System (ADS)
Xue, Zheng-Yuan
2013-04-01
We propose a scheme to implement controlled not gate for topological qubits in a quantum-dot and Majorana fermion hybrid system. Quantum information is encoded on pairs of Majorana fermions, which live on the the interface between topologically trivial and nontrivial sections of a quantum nanowire deposited on an s-wave superconductor. A measurement based two-qubit controlled not gate is produced with the help of parity measurements assisted by the quantum-dot and followed by prescribed single-qubit gates. The parity measurement, on the quantum-dot and a topological qubit, is achieved by the Aharonov-Casher effect.
Afifi, A F
1978-01-01
Differences were found in the counts and occurrence of fungi in the phyllosphere and thizosphere of two representatives of the Lamiacea family, Origanum majorana and Ocimum basilicum, and in the phyllosphere and rhizosphere of Phaseolus vulgaris growing separately or in coenosis with O. majorana or O. basilicum. Both the volatile substances released from ground leaves of the two latter plant species and the root exudates affected considerably spore germination of isolated phylospheric and rhizospheric fungi. The results indicated a possible role of root exudates and volatile substances released from leaves in colonization of rhizosphere and/or phyllosphere by fungi, especially in associations of various plants.
NASA Astrophysics Data System (ADS)
Aloisio, Giovanni; Fiore, Sandro; Negro, A.
2010-05-01
The CMCC Data Distribution Centre (DDC) is the primary entry point (web gateway) to the CMCC. It is a Data Grid Portal providing a ubiquitous and pervasive way to ease data publishing, climate metadata search, datasets discovery, metadata annotation, data access, data aggregation, sub-setting, etc. The grid portal security model includes the use of HTTPS protocol for secure communication with the client (based on X509v3 certificates that must be loaded into the browser) and secure cookies to establish and maintain user sessions. The CMCC DDC is now in a pre-production phase and it is currently used only by internal users (CMCC researchers and climate scientists). The most important component already available in the CMCC DDC is the Search Engine which allows users to perform, through web interfaces, distributed search and discovery activities by introducing one or more of the following search criteria: horizontal extent (which can be specified by interacting with a geographic map), vertical extent, temporal extent, keywords, topics, creation date, etc. By means of this page the user submits the first step of the query process on the metadata DB, then, she can choose one or more datasets retrieving and displaying the complete XML metadata description (from the browser). This way, the second step of the query process is carried out by accessing to a specific XML document of the metadata DB. Finally, through the web interface, the user can access to and download (partially or totally) the data stored on the storage device accessing to OPeNDAP servers and to other available grid storage interfaces. Requests concerning datasets stored in deep storage will be served asynchronously.
RTEMS CENTRE - Support and Maintenance CENTRE to RTEMS Operating System
NASA Astrophysics Data System (ADS)
Silva, H.; Constantino, A.; Mota, M.; Freitas, D.; Zulianello, M.
2007-08-01
Real Time Operating System for Multiprocessor Systems (RTEMS) CENTRE is a project under the ESA-Portugal Task Force aiming to develop a support and maintenance centre to RTEMS operating system. The project can be summarized in two main streams, first one related to design, development, maintenance and integration of tools to augment and sustain RTEMS operating system and second stream linked to the creation of technical competences with a support site to RTEMS operating system in Europe. RTEMS CENTRE intends to minimize the cost of the incorporation/integration of airborne and space applications in this Real Time Operating System. The centre started officially in the 15th of November 2006 and is currently in the study definition and system engineering phase.
The cosmogenic induced background estimation for the MAJORANA DEMONSTRATOR enriched 76Ge
NASA Astrophysics Data System (ADS)
White, Brandon; Majorana Collaboration
2016-03-01
Neutrino-less double beta (0 νββ) decay experiments probe for such rare events that the suppression of backgrounds are major experimental concerns. Cosmogenic induced isotopes have the potential to be a major background for such experiments. For the MAJORANA DEMONSTRATOR Experiment 76Ge isotope is used as both detector and source. The isotope 68Ge is cosmogenically produced when the Ge is on the Earth's surface. The decay of this isotope can mimic events in the region of interest. The experiment is located at the 4850 foot level at the Sanford Underground Research Facility in Lead, South Dakota to suppress cosmogenic activation. In this talk I will present the calculations of cosmogenic background for the enriched 76Ge materials used in the MAJORANA DEMONSTRATOR HPGe detectors. The activation is determined by the surface exposure from the time of production, storage, and delivery of the enriched Ge detectors to the underground experimental site. This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics, the Particle Astrophysics and Nuclear Physics Programs of the National Science Foundation, and the Sanford Underground Research Faci.
Quantum memories with zero-energy Majorana modes and experimental constraints
NASA Astrophysics Data System (ADS)
Ippoliti, Matteo; Rizzi, Matteo; Giovannetti, Vittorio; Mazza, Leonardo
2016-06-01
In this work we address the problem of realizing a reliable quantum memory based on zero-energy Majorana modes in the presence of experimental constraints on the operations aimed at recovering the information. In particular, we characterize the best recovery operation acting only on the zero-energy Majorana modes and the memory fidelity that can be therewith achieved. In order to understand the effect of such restriction, we discuss two examples of noise models acting on the topological system and compare the amount of information that can be recovered by accessing either the whole system, or the zero modes only, with particular attention to the scaling with the size of the system and the energy gap. We explicitly discuss the case of a thermal bosonic environment inducing a parity-preserving Markovian dynamics in which the memory fidelity achievable via a read-out of the zero modes decays exponentially in time, independent from system size. We argue, however, that even in the presence of said experimental limitations, the Hamiltonian gap is still beneficial to the storage of information.
Detecting a Majorana-Fermion Zero Mode Using a Quantum Dot
NASA Astrophysics Data System (ADS)
Liu, Dong E.; Baranger, Harold U.
2012-02-01
We propose an setup for detecting a Majorana zero mode consisting of a spinless quantum dot coupled to the end of a p-wave superconducting nanowire [1]. The conductance through the dot is monitored by adding two external leads. We find that the Majorana bound state at the end of the wire strongly influences the conductance through the quantum dot: driving the wire through the topological phase transition causes a sharp jump in the conductance by a factor of 1/2. In the topological phase, the zero temperature peak value of the dot conductance (i.e. on resonance and symmetric coupling) is e^2/2h. In contrast, if the wire is in its trivial phase, the peak is e^2/h, or if a regular fermionic zero mode occurs, the conductance is 0. We also consider coupling the dot to both ends of the wire (two MBS), with a magnetic flux f through the loop. The conductance as a function of phase shows peaks at f/f0 = (2n+1)*pi which can be used to tune Flensberg's qubit system [PRL (2011)] to the energy degeneracy point. [4pt] [1] D. E. Liu and H. U. Baranger, PRB in press (2011); arXiv/1107.4338.
Molecular Andreev bound states and Majorana modes in a double dot system
NASA Astrophysics Data System (ADS)
Vernek, Edson; Silva, Joelson F.
Nanostructured systems such as quantum dots (QD) connected to superconductors has attracted a lot of attention in the recent years. One of the well known phenomena in such a system is the formation of a pair of bound called Andreev bound states (ABS). Recently, it have been shown that when a QD is coupled to a topological superconductor wire, a Majorana bound state (MBS) leaks from the end of the wire into the dot. The character of these bound states is much reacher in structures like molecules and is far from being completely understood. In this work we study a system composed by a two inter-connected QDs in which one of then is coupled to a normal superconductor and to a normal lead while the other is coupled to a topological superconductor and to a distinct normal metallic lead. We show that in the atomic limit (for small interdot coupling), one of the dot has a pair of ABS whereas the other has a single a MBS. More interestingly, in the molecular regime (large inter-dot coupling) we observe a localized Majorana mode coexisting with a delocalized molecular ABS. We would like to thank financial support from the Brazilian agencies CNPq, CAPES and FAPEMIG.
NASA Astrophysics Data System (ADS)
Benalcazar, Wladimir; Teo, Jeffrey; Hughes, Taylor; InstituteCondensed Matter Physics Team
2014-03-01
We classify discrete-rotation symmetric topological crystalline superconductors (TCS) in two dimensions and provide the criteria for a zero energy Majorana bound state (MBS) to be present at composite defects made from magnetic flux, dislocations, and disclinations. In addition to the Chern number that encodes chirality, discrete rotation symmetry further divides TCS into distinct stable topological classes according to the rotation eigenspectrum of Bogoliubov-de Gennes quasi-particles. Conical crystalline defects are shown to be able to accommodate robust MBS when a certain combination of these bulk topological invariants is non-trivial as dictated by the index theorems proved within. The number parity of MBS is counted by a Z2-valued index that solely depends on the disclination and the topological class of the TCS. We also discuss the implications for corner-bound Majorana modes on the boundary of topological crystalline superconductors J.C.Y.T. acknowledges support from the Simons Foundation Fellowship. T.L.H. was supported by ONR Grant No. N0014-12-1-0935. We also thanks the support of the UIUC ICMT.
Cosmic ray electron and positron excesses from a fourth generation heavy Majorana neutrino
Masina, Isabella; Sannino, Francesco E-mail: sannino@cp3-origins.net
2011-08-01
Unexpected features in the energy spectra of cosmic rays electrons and positrons have been recently observed by PAMELA and Fermi-LAT satellite experiments, opening to the exciting possibility of an indirect manifestation of new physics. A TeV-scale fourth lepton family is a natural extension of the Standard Model leptonic sector (also linked to the hierarchy problem in Minimal Walking Technicolor models). The heavy Majorana neutrino of this setup mixes with Standard Model charged leptons through a weak charged current interaction. Here, we first study analytically the energy spectrum of the electrons and positrons originated in the heavy Majorana neutrino decay modes, also including polarization effects. We then compare the prediction of this model with the experimental data, exploiting both the standard direct method and our recently proposed Sum Rules method. We find that the decay modes involving the tau and/or the muon charged leptons as primary decay products fit well the PAMELA and Fermi-LAT lepton excesses while there is tension with respect to the antiproton to proton fraction constrained by PAMELA.
Majorana bound state of a Bogoliubov-de Gennes-Dirac Hamiltonian in arbitrary dimensions
NASA Astrophysics Data System (ADS)
Imura, Ken-Ichiro; Fukui, Takahiro; Fujiwara, Takanori
2012-01-01
We study a Majorana zero-energy state bound to a hedgehog-like point defect in a topological superconductor described by a Bogoliubov-de Gennes (BdG)-Dirac type effective Hamiltonian. We first give an explicit wave function of a Majorana state by solving the BdG equation directly, from which an analytical index can be obtained. Next, by calculating the corresponding topological index, we show a precise equivalence between both indices to confirm the index theorem. Finally, we apply this observation to reexamine the role of another topological invariant, i.e., the Chern number associated with the Berry curvature proposed in the study of protected zero modes along the lines of topological classification of insulators and superconductors. We show that the Chern number is equivalent to the topological index, implying that it indeed reflects the number of zero-energy states. Our theoretical model belongs to the BDI class from the viewpoint of symmetry, whereas the spatial dimension d of the system is left arbitrary throughout the paper.
NASA Astrophysics Data System (ADS)
Khezerlou, Maryam; Goudarzi, Hadi; Asgarifar, Samin
2017-03-01
Among the potential applications of topological insulators, we theoretically study the coexistence of proximity-induced ferromagnetic and superconducting orders in the surface states of a 3-dimensional topological insulator. The superconducting electron-hole excitations can be significantly affected by the magnetic order induced by a ferromagnet. In one hand, the surface state of the topological insulator, protected by the time-reversal symmetry, creates a spin-triplet and, on the other hand, magnetic order causes to renormalize the effective superconducting gap. We find Majorana mode energy along the ferromagnet/superconductor interface to sensitively depend on the magnitude of magnetization mzfs from superconductor region, and its slope around perpendicular incidence is steep with very low dependency on mzfs. The superconducting effective gap is renormalized by a factor η(mzfs), and Andreev bound state in ferromagnet-superconductor/ferromagnet/ferromagnet-superconductor (FS/F/FS) Josephson junction is more sensitive to the magnitude of magnetizations of FS and F regions. In particular, we show that the presence of mzfs has a noticeable impact on the gap opening in Andreev bound state, which occurs in finite angle of incidence. This directly results in zero-energy Andreev state being dominant. By introducing the proper form of corresponding Dirac spinors for FS electron-hole states, we find that via the inclusion of mzfs, the Josephson supercurrent is enhanced and exhibits almost abrupt crossover curve, featuring the dominant zero-energy Majorana bound states.
A search for a heavy Majorana neutrino and a radiation damage simulation for the HF detector
NASA Astrophysics Data System (ADS)
Wetzel, James William
A search for heavy Majorana neutrinos is performed using an event signature defined by two same-sign muons accompanied by two jets. This search is an extension of previous searches, (L3, DELPHI, CMS, ATLAS), using 19.7 fb -1 of data from the 2012 Large Hadron Collider experimental run collected by the Compact Muon Solenoid experiment. A mass window of 40-500 GeV/ c2 is explored. No excess events above Standard Model backgrounds is observed, and limits are set on the mixing element squared, |VmuN|2, as a function of Majorana neutFnrino mass. The Hadronic Forward (HF) Detector's performance will degrade as a function of the number of particles delivered to the detector over time, a quantity referred to as integrated luminosity and measured in inverse femtobarns (fb-1). In order to better plan detector upgrades, the CMS Forward Calorimetry Task Force (FCAL) group and the CMS Hadronic Calorimeter (HCAL) group have requested that radiation damage be simulated and the subsequent performance of the HF subdetector be studied. The simulation was implemented into both the CMS FastSim and CMS FullSim simulation packages. Standard calorimetry performance metrics were computed and are reported. The HF detector can expect to perform well through the planned delivery of 3000 fb-1.
Spin-orbit coupling in InSb semiconductor nanowires: physical limits for majorana states
NASA Astrophysics Data System (ADS)
Sipahi, Guilherme; de Campos, Tiago; Faria Junior, Paulo E.; Gmitra, Martin; Zutic, Igor; Fabian, Jaroslav
The search for Majorana fermions is a hot subject nowadays. One of the possibilities for their realization is the use of semiconductor nanowires and p-type superconductors coupled together. Following this path, the first step is the determination of realistic band structures of these wires including spin-orbit effects. To consider the spin-orbit effects, its common to use models that take into account only the first conduction band. Although these reduced models have been successfully used to determine some physical properties, a more realistic description of the spin-orbit coupling between the bands is required to further investigate possible ways to realize the Majorana fermions. In this study we use a state of the art 14 band k.p formalism together with the envelope function approach to determine the band structure of InAs semiconductor nanowires and analyze how the quantum confinement change the coupling between the bands. As a result we have extracted the effective masses and the spin-orbit splitting for a large range of nanowire radial sizes and for several conduction bands that can be used in effective models. FAPESP (No. 2011/19333-4, No. 2012/05618-0 and No. 2013/23393-8), CNPq (No. 246549/2012-2 and No. 149904/2013-4), CAPES(PVE 88881.068174/2014-01) and DFG SFB 689.
Extended scaling and residual flavor symmetry in the neutrino Majorana mass matrix
NASA Astrophysics Data System (ADS)
Samanta, Rome; Roy, Probir; Ghosal, Ambar
2016-12-01
The residual symmetry approach, along with a complex extension for some flavor invariance, is a powerful tool to uncover the flavor structure of the 3 × 3 neutrino Majorana mass matrix M_ν toward gaining insights into neutrino mixing. We utilize this to propose a complex extension of the real scaling ansatz for M_ν which was introduced some years ago. Unlike the latter, our proposal allows a nonzero mass for each of the three light neutrinos as well as a nonvanishing θ _{13}. The generation of light neutrino masses via the type-I seesaw mechanism is also demonstrated. A major result of this scheme is that leptonic Dirac CP-violation must be maximal while atmospheric neutrino mixing does not need to be exactly maximal. Moreover, each of the two allowed Majorana phases, to be probed by the search for nuclear 0ν β β decay, has to be at one of its two CP-conserving values. There are other interesting consequences such as the allowed occurrence of a normal mass ordering which is not favored by the real scaling ansatz. Our predictions will be tested in ongoing and future neutrino oscillation experiments at T2K, NOν A and DUNE.
Symmetry-protected non-Abelian braiding of Majorana Kramers pairs
NASA Astrophysics Data System (ADS)
Gao, Pin; He, Ying-Ping; Liu, Xiong-Jun
2016-12-01
We develop a complete theory for symmetry protected non-Abelian statistics of Majorana Kramers' pairs (MKPs) in time-reversal (TR) invariant topological superconductors, with fundamental results being uncovered. By introducing an effective Hamiltonian approach to describe the braiding of MKPs, we show that the non-Abelian braiding is protected when the effective Hamiltonian exhibits a new TR-like antiunitary symmetry, which is satisfied if the system is free of dynamical noise. Importantly, even the dynamical noise cannot cause error in braiding, unless the noise correlation function breaks a dynamical TR symmetry. This is a profound result and generalizes the TR symmetry protection of MKPs to the dynamical regime. Moreover, the resulted error by noise is shown to be a higher-order effect, compared with the decoherence of Majorana qubits without TR symmetry protection. This study completes the theory of symmetry-protected non-Abelian statistics of MKPs, and shows that the non-Abelian braiding of MKPs is well observable and may have versatile applications to future quantum computation technologies.
NASA Astrophysics Data System (ADS)
Mishmash, Ryan V.; Aasen, David; Hell, Michael; Higginbotham, Andrew; Danon, Jeroen; Leijnse, Martin; Jespersen, Thomas S.; Folk, Joshua A.; Marcus, Charles M.; Flensberg, Karsten; Alicea, Jason
We introduce a scheme for preparation, manipulation, and readout of Majorana zero modes in semiconducting wires coated with mesoscopic superconducting islands. Our approach synthesizes recent advances in materials growth with tools commonly used in quantum-dot experiments, including gate-control of tunnel barriers and Coulomb effects, charge sensing, and charge pumping. Recently, we have outlined a sequence of relatively modest milestones which interpolate between zero-mode detection and longer term quantum computing applications. In this talk, I will discuss two of these milestones: (1) detection of fusion rules for non-Abelian anyons using either proximal charge sensing or Majorana-mediated charge pumping and (2) validation of a prototype topological qubit via unconventional scaling relations between the time-averaged qubit splitting and its decoherence times T1 and T2. Both of these proposed experiments require only a single wire with two islands--a hardware configuration already available in the laboratory. Furthermore, these pre-braiding experiments can be adapted to other manipulation and readout schemes as well.
ν-K0 Analogy, Dirac-Majorana Neutrino Duality and the Neutrino Oscillations
NASA Astrophysics Data System (ADS)
Lipmanov, E. M.
The intent of this paper is to convey a new primary physical idea of a Dirac-Majorana neutrino duality in relation to the topical problem of neutrino oscillations. In view of the new atmospheric, solar and the LSND neutrino oscillation data, the Pontecorvo ν - K0 oscillation analogy is generalized to the notion of neutrino duality with substantially different physical meaning ascribed to the long-baseline and the short-baseline neutrino oscillations. At the level of CP-invariance, the suggestion of dual neutrino properties defines the symmetric two-mixing-angle form of the widely discussed four-neutrino (2 +2)-mixing scheme, as a result of the lepton charge conservation selection rule and a minimum of two Dirac neutrino fields. With neutrino duality, the two-doublet structure of the Majorana neutrino mass spectrum is a vestige of the two-Dirac-neutrino origin. The fine neutrino mass doublet structure is natural because it is produced by a lepton charge symmetry violating perturbation on a zero-approximation system of two twofold mass-degenerate Dirac neutrino-antineutrino pairs. A set of inferences related to the neutrino oscillation phenomenology in vacuum is considered.
Baâtour, Olfa; Tarchoune, Imen; Mahmoudi, Hela; Nassri, Nawel; Abidi, Wissal; Kaddour, Rym; Hamdaoui, Ghaith; Nasri-Ayachi, Mouhiba Ben; Lachaâl, Mohtar; Marzouk, Brahim
2012-06-01
O. majorana shoots were investigated for their essential oil (EO) composition. Two experiments were carried out; the first on hydroponic medium in a culture chamber and the second on inert sand in a greenhouse for 20 days. Plants were cultivated for 17 days in hydroponic medium supplemented with NaCl 100 mmol L⁻¹. The results showed that the O. majorana hydroponic medium offered higher essential oil yield than that from the greenhouse. The latter increased significantly in yield (by 50 %) under saline constraint while it did not change in the culture chamber. Under greenhouse conditions and in the absence of salt treatment, the major constituents were terpinen-4-ol and trans-sabinene hydrate. However, in the culture chamber, the major volatile components were cis-sabinene hydrate and terpinen-4-ol. In the presence of NaCl, new compounds appeared, such as eicosane, spathulenol, eugenol, and phenol. In addition, in the greenhouse, with or without salt, a very important change of trans-sabinene hydrate concentration in EO occurred, whereas in the culture chamber change appeared in cis-sabinene hydrate content.
Effect of chiral symmetry on chaotic scattering from Majorana zero modes.
Schomerus, H; Marciani, M; Beenakker, C W J
2015-04-24
In many of the experimental systems that may host Majorana zero modes, a so-called chiral symmetry exists that protects overlapping zero modes from splitting up. This symmetry is operative in a superconducting nanowire that is narrower than the spin-orbit scattering length, and at the Dirac point of a superconductor-topological insulator heterostructure. Here we show that chiral symmetry strongly modifies the dynamical and spectral properties of a chaotic scatterer, even if it binds only a single zero mode. These properties are quantified by the Wigner-Smith time-delay matrix Q=-iℏS^{†}dS/dE, the Hermitian energy derivative of the scattering matrix, related to the density of states by ρ=(2πℏ)^{-1}TrQ. We compute the probability distribution of Q and ρ, dependent on the number ν of Majorana zero modes, in the chiral ensembles of random-matrix theory. Chiral symmetry is essential for a significant ν dependence.
Minister unveils new nanotech centres
NASA Astrophysics Data System (ADS)
Dumé, Belle
2009-06-01
Three new nanotechnology research centres are to be set up in France as part of a €70m government plan to help French companies in the sector. Researchers at the new centres, which will be located in Grenoble, Saclay (near Paris) and Toulouse, will be encouraged to collaborate with industry to develop new nanotech-based products. Dubbed NANO-INNOV, the new plan includes €46m for two new buildings at Saclay, with the rest being used to buy new equipment at the three centres and to fund grant proposals from staff to the French National Research Agency (ANR).
NASA Astrophysics Data System (ADS)
Zichichi, A.
2014-06-01
The Ettore Majorana Foundation and Centre for Scientific Culture (EMFCSC) is celebrating its 50th Anniversary over the three years 2011-2013. This year will be the second of the three devoted to the celebrations of the 50th Anniversary. Why three years? The EMFCSC started in 1961 when, with my great friend John Bell, I discussed the problem of creating a bridge between university courses and activities in advanced physics laboratories such as CERN. A year later, on May 8th at CERN, Bell, Patrick Blackett, Victor Weisskopf, Isidor Rabi and Zichichi formally established the EMFCSC. The Centre's first activity was the School of Subnuclear Physics at Erice in 1963. This is why the celebrations are over three years. In 2011, the discovery of the negative sign of the β-function and of asymptotic freedom was celebrated. In 2013, the SSB plus Instantons will be celebrated. In 2012 we celebrate QCD...
NASA Astrophysics Data System (ADS)
Rajak, Atanu; Dutta, Amit
2014-04-01
We consider the temporal evolution of a zero-energy edge Majorana of a spinless p-wave superconducting chain following a sudden change of a parameter of the Hamiltonian. Starting from one of the topological phases that has an edge Majorana, the system is suddenly driven to the other topological phase or to the (topologically) trivial phases and to the quantum critical points (QCPs) separating these phases. The survival probability of the initial edge Majorana as a function of time is studied following the quench. Interestingly when the chain is quenched to the QCP, we find a nearly perfect oscillation of the survival probability, indicating that the Majorana travels back and forth between two ends, with a time period that scales with the system size. We also generalize to the situation when there is a next-nearest-neighbor hopping in a superconducting chain and there results in a pair of edge Majorana at each end of the chain in the topological phase. We show that the frequency of oscillation of the survival probability gets doubled in this case. We also perform an instantaneous quenching of the Hamiltonian (with two Majorana modes at each end of the chain) to an another Hamiltonian which has only one Majorana mode in equilibrium; the MSP shows oscillations as a function of time with a noticeable decay in the amplitude. On the other hand for a quenching which is reverse to the previous one, the MSP decays rapidly and stays close to zero with fluctuations in amplitude.
NASA Astrophysics Data System (ADS)
Nori, Franco
2014-03-01
We study a heterostructure which consists of a topological insulator and a superconductor with a hole. This system supports a robust Majorana fermion state bound to the vortex core. We study the possibility of using scanning tunneling spectroscopy (i) to detect the Majorana fermion in this setup and (ii) to study excited states bound to the vortex core. The Majorana fermion manifests itself as an H-dependent zero-bias anomaly of the tunneling conductance. The excited states spectrum differs from the spectrum of a typical Abrikosov vortex, providing additional indirect confirmation of the Majorana state observation. We also study how to manipulate and probe Majorana fermions using super-conducting circuits. In we consider a semiconductor nanowire quantum dot with strong spin-orbit coupling (SOC), which can be used to achieve a spin-orbit qubit. In contrast to a spin qubit, the spin-orbit qubit can respond to an external ac electric field, i.e., electric-dipole spin resonance. We develop a theory that can apply in the strong SOC regime. We find that there is an optimal SOC strength ηopt = √ 2/2, where the Rabi frequency induced by the ac electric field becomes maximal. Also, we show that both the level spacing and the Rabi frequency of the spin-orbit qubit have periodic responses to the direction of the external static magnetic field. These responses can be used to determine the SOC in the nanowire. FN is partly supported by the RIKEN CEMS, iTHES Project, MURI Center for Dynamic Magneto-Optics, JSPS-RFBR Contract No. 12-02-92100, Grant-in-Aid for Scientific Research (S), MEXT Kakenhi on Quantum Cybernetics, and the JSPS via its FIRST program.
NASA Astrophysics Data System (ADS)
Sharma, Girish; Tewari, Sumanta
2016-05-01
It has been recently pointed out that the use of a superconducting (SC) lead instead of a normal metal lead can suppress the thermal broadening effects in tunneling conductance from Majorana fermions, helping reveal the quantized conductance of 2 e2/h . In this paper we discuss the specific case of tunneling conductance with SC leads of spin-orbit coupled semiconductor-superconductor (SM-SC) heterostructures in the presence of a Zeeman field, a system which has been extensively studied both theoretically and experimentally using a metallic lead. We examine the d I /d V spectra using a SC lead for different sets of physical parameters including temperature, tunneling strength, wire length, magnetic field, and induced SC pairing potential in the SM nanowire. We conclude that in a finite wire the Majorana splitting energy Δ E , which has nontrivial dependence on these physical parameters, remains responsible for the d I /d V peak broadening, even when the temperature broadening is suppressed by the SC gap in the lead. In a finite wire the signatures of Majorana fermions with a SC lead are oscillations of quasi-Majorana peaks about bias V =±Δlead , in contrast to the case of metallic leads where such oscillations are about zero bias. Our results will be useful for analysis of future experiments on SM-SC heterostructures using SC leads.
Abgrall, N.; Aguayo, E.; Avignone, F. T.; ...
2017-02-16
Here, we report the first measurement of the total muon flux underground at the Davis Campus of the Sanford Underground Research Facility at the 4850 ft level. Measurements were performed using the MajoranaDemonstratormuon veto system arranged in two different configurations. The measured total flux is (5.31±0.17)×10–9μ/s/cm2.
NASA Astrophysics Data System (ADS)
Girardi, I.; Petcov, S. T.; Titov, A. V.
2016-10-01
We obtain predictions for the Majorana phases α21 / 2 and α31 / 2 of the 3 × 3 unitary neutrino mixing matrix U = Ue† Uν, Ue and Uν being the 3 × 3 unitary matrices resulting from the diagonalisation of the charged lepton and neutrino Majorana mass matrices, respectively. We focus on forms of Ue and Uν permitting to express α21 / 2 and α31 / 2 in terms of the Dirac phase δ and the three neutrino mixing angles of the standard parametrisation of U, and the angles and the two Majorana-like phases ξ21 / 2 and ξ31 / 2 present, in general, in Uν. The concrete forms of Uν considered are fixed by, or associated with, symmetries (tri-bimaximal, bimaximal, etc.), so that the angles in Uν are fixed. For each of these forms and forms of Ue that allow to reproduce the measured values of the three neutrino mixing angles θ12, θ23 and θ13, we derive predictions for phase differences (α21 / 2 -ξ21 / 2), (α31 / 2 -ξ31 / 2), etc., which are completely determined by the values of the mixing angles. We show that the requirement of generalised CP invariance of the neutrino Majorana mass term implies ξ21 = 0 or π and ξ31 = 0 or π. For these values of ξ21 and ξ31 and the best fit values of θ12, θ23 and θ13, we present predictions for the effective Majorana mass in neutrinoless double beta decay for both neutrino mass spectra with normal and inverted ordering.
The digital eczema centre utrecht.
van Os-Medendorp, Harmieke; van Veelen, Carien; Hover, Maaike; Eland-de Kok, Petra; Bruijnzeel-Koomen, Carla; Sonnevelt, Gert-Jan; Mensing, Geert; Pasmans, Suzanne
2010-01-01
The University Medical Centre Utrecht (UMC Utrecht) has developed an eczema portal that combines e-consulting, monitoring and self-management training by a dermatology nurse online for patients and parents of young children with atopic dermatitis (AD). Patient satisfaction with the portal was high. It could be extended to become a Digital Eczema Centre for multidisciplinary collaboration between health-care providers from different locations and the patient. Before starting the construction of the Digital Eczema Centre, the feasibility was examined by carrying out a business case analysis. The purposes, strength and weaknesses showed that the Digital Eczema Centre offered opportunities to improve care for patients with AD. The financial analysis resulted in a medium/best case scenario with a positive result of euro50-240,000 over a period of five years. We expect that the Digital Eczema Centre will increase the accessibility and quality of care. The web-based patient record and the digital chain-of-care promote the involvement of patients, parents and multidisciplinary teams as well as the continuity and coordination of care.
Transport properties of paired Majorana bound states in a parallel junction
NASA Astrophysics Data System (ADS)
Jiang, Cui; Gong, W. J.; Zheng, Yi-Song
2013-12-01
The transport properties of a paired Majorana bound states (MBSs) in a parallel junction are theoretically investigated, by considering the influence of different MBS-lead coupling manners, i.e., left-right asymmetric coupling, upper-down asymmetric coupling, and left-right upper-down asymmetric coupling. The calculation results show that the MBS-lead coupling manners affect the transport properties in a substantial way. For the former two configurations, the shot noise Fano factor in the zero-bias limit is related to the value of the conductance maximum with F0=1+1/2Tmax (conductance G =e/2hT). When both the left-right and upper-down symmetries are broken, such a relation is modified into F0=1-12/T0. These results will be helpful for describing the transport characteristics of the junction with MBSs.
NASA Astrophysics Data System (ADS)
Kawakami, Takuto; Hu, Xiao
2016-01-01
We investigate one-dimensional (1D) Majorana bound states (MBSs) realized in terms of the helical edge states of a 2D quantum spin-Hall insulator in a heterostructure with a superconducting substrate and two ferromagnetic insulators (FIs). By means of Bogoliubov-de Gennes approach we demonstrate that there is a helical spin texture in the MBS wave function with a pitch proportional to the Fermi momentum. Moreover, simultaneous detection on local density of states by scanning tunneling microscopy and spectroscopy at a position close to one FI edge and at the midpoint between the two FIs can not only map out the energy spectrum ±E cos(ϕ/2) where ϕ is the relative angle between the magnetizations of two FIs, but also prove experimentally that the two quasiparticle excitations do not mix with each other as protected by the parity conservation associated with the MBSs.
Fermion Parity Flips and Majorana Defects in Superconducting Fractional Topological Phases
NASA Astrophysics Data System (ADS)
Khan, Mayukh; Teo, Jeffrey; Hughes, Taylor; Vishveshwara, Smitha
We consider layered heterojunctions of s-wave superconductors and Abelian topologically ordered (TO) phases. We derive the emergent theories for a wide variety of fractional quantum Hall states promoted by a ℤ2 gauge theory. The theory always carries an anyonic symmetry (AS) which effects a fermion parity flip. The associated twist defects, which flip the parities of some types of orbiting quasiparticles, trap ordinary zero energy Majorana bound states (MBS), and can bind fractional charge. For example, an h / 2 e flux vortex of the superconductor that circulates around the MBS undergoes a fermion parity flip and is accompanied by a level crossing in the vortex energy spectrum. We show numerical evidence of the level crossing in the simplest examples: a Chern insulator and a normal insulator/topological insulator/superconductor junction. Finally, we briefly describe the resulting twist liquid theory after gauging the AS where the twist defects become deconfined anyonic excitations.
Dai, Li; Kuo, Watson; Chung, Ming-Chiang
2015-06-10
We propose a scheme for extracting entangled charge qubits from quantum-dot chains that support zero-energy edge modes. The edge mode is composed of Majorana fermions localized at the ends of each chain. The qubit, logically encoded in double quantum dots, can be manipulated through tunneling and pairing interactions between them. The detailed form of the entangled state depends on both the parity measurement (an even or odd number) of the boundary-site electrons in each chain and the teleportation between the chains. The parity measurement is realized through the dispersive coupling of coherent-state microwave photons to the boundary sites, while the teleportation is performed via Bell measurements. Our scheme illustrates localizable entanglement in a fermionic system, which serves feasibly as a quantum repeater under realistic experimental conditions, as it allows for finite temperature effect and is robust against disorders, decoherence and quasi-particle poisoning.
The Majorana Demonstrator for 0νββ: Current Status and Future Plans
Green, Matthew P.; Avignone, F. T.; Galindo-Uribarri, Alfredo; Radford, David C; Romero-Romero, Elisa; Varner, Jr, Robert L; White, Brandon R; Wilkerson, J. F.
2015-01-01
The Majorana Demonstrator will search for neutrinoless-double-beta decay (0νββ) in 76Ge, while establishing the feasibility of a future tonne-scale germanium-based 0νββ experiment, and performing searches for new physics beyond the Standard Model. The experiment, currently under construction at the Sanford Underground Research Facility in Lead, SD, will consist of a pair of modular high-purity germanium detector arrays housed inside of a compact copper, lead, and polyethylene shield. Through a combination of strict materials qualifications and assay, low-background design, and powerful background rejection techniques, the Demonstrator aims to achieve a background rate in the 0νββ region of interest (ROI) of no more than 3cnts/(ROI-t-y). The current status of the Demonstrator is discussed, as are plans for its completion.
NASA Astrophysics Data System (ADS)
Pawlak, Rémy; Kisiel, Marcin; Klinovaja, Jelena; Meier, Tobias; Kawai, Shigeki; Glatzel, Thilo; Loss, Daniel; Meyer, Ernst
2016-11-01
Motivated by the striking promise of quantum computation, Majorana bound states (MBSs) in solid-state systems have attracted wide attention in recent years. In particular, the wavefunction localisation of MBSs is a key feature and is crucial for their future implementation as qubits. Here we investigate the spatial and electronic characteristics of topological superconducting chains of iron atoms on the surface of Pb(110) by combining scanning tunnelling microscopy and atomic force microscopy. We demonstrate that the Fe chains are mono-atomic, structured in a linear manner and exhibit zero-bias conductance peaks at their ends, which we interpret as signature for a MBS. Spatially resolved conductance maps of the atomic chains reveal that the MBSs are well localised at the chain ends (≲25 nm), with two localisation lengths as predicted by theory. Our observation lends strong support to use MBSs in Fe chains as qubits for quantum-computing devices.
Synthesizing Majorana zero-energy modes in a periodically gated quantum wire
NASA Astrophysics Data System (ADS)
Malard, Mariana; Japaridze, George I.; Johannesson, Henrik
2016-09-01
We explore a scheme for engineering a one-dimensional spinless p -wave superconductor hosting unpaired Majorana zero-energy modes, using an all-electric setup with a spin-orbit-coupled quantum wire in proximity to an s -wave superconductor. The required crossing of the Fermi level by a single spin-split energy band is ensured by employing a periodically modulated Rashba interaction, which, assisted by electron-electron interactions and a uniform Dresselhaus interaction, opens a gap at two of the spin-orbit shifted Fermi points. While an implementation in a hybrid superconductor-semiconductor device requires improvements upon present-day capabilities, a variant of our scheme where spin-orbit-coupled cold fermions are effectively proximity coupled to a BEC reservoir of Feshbach molecules may provide a ready-to-use platform.
Majorana bound state in a coupled quantum-dot hybrid-nanowire system.
Deng, M T; Vaitiekėnas, S; Hansen, E B; Danon, J; Leijnse, M; Flensberg, K; Nygård, J; Krogstrup, P; Marcus, C M
2016-12-23
Hybrid nanowires combining semiconductor and superconductor materials appear well suited for the creation, detection, and control of Majorana bound states (MBSs). We demonstrate the emergence of MBSs from coalescing Andreev bound states (ABSs) in a hybrid InAs nanowire with epitaxial Al, using a quantum dot at the end of the nanowire as a spectrometer. Electrostatic gating tuned the nanowire density to a regime of one or a few ABSs. In an applied axial magnetic field, a topological phase emerges in which ABSs move to zero energy and remain there, forming MBSs. We observed hybridization of the MBS with the end-dot bound state, which is in agreement with a numerical model. The ABS/MBS spectra provide parameters that are useful for understanding topological superconductivity in this system.
Resonant Raman scattering theory for Kitaev models and their Majorana fermion boundary modes
NASA Astrophysics Data System (ADS)
Perreault, Brent; Knolle, Johannes; Perkins, Natalia B.; Burnell, F. J.
2016-09-01
We study the inelastic light scattering response in two- (2D) and three-dimensional (3D) Kitaev spin-liquid models with Majorana spinon band structures in the symmetry classes BDI and D leading to protected gapless surface modes. We present a detailed calculation of the resonant Raman/Brillouin scattering vertex relevant to iridate and ruthenate compounds whose low-energy physics is believed to be proximate to these spin-liquid phases. In the symmetry class BDI, we find that while the resonant scattering on thin films can detect the gapless boundary modes of spin liquids, the nonresonant processes do not couple to them. For the symmetry class D, however, we find that the coupling between both types of light-scattering processes and the low-energy surface states is strongly suppressed. Additionally, we describe the effect of weak time-reversal symmetry breaking perturbations on the bulk Raman response of these systems.
NASA Astrophysics Data System (ADS)
Wakatsuki, Ryohei; Ezawa, Motohiko; Nagaosa, Naoto
2014-05-01
Motivated by the InSb nanowire superconductor system, we investigate a system where one-dimensional topological superconductors are placed in parallel. It would be simulated well by a ladder of the Kitaev chains. The system undergoes multiple topological phase transitions, where the number of Majorana fermions changes as a function of the interchain superconducting pairings. We analytically determine the topological phase diagram by explicitly calculating the topological number and the band structure. They show even-odd effects with respect to the number of legs of the ladder. When the relative phase between the inter- and intrachain superconducting pairings is 0 or π, the system belongs to the class BDI characterized by the Z index, and otherwise it belongs to the class D characterized by the Z2 index. This topological class change would be caused by applying the Josephson current or an external magnetic field, and could be observed by measuring the zero-bias differential conductance.
Yu, Li-Wei; Ge, Mo-Lin
2015-01-01
A new realization of doubling degeneracy based on emergent Majorana operator Γ presented by Lee-Wilczek has been made. The Hamiltonian can be obtained through the new type of solution of Yang-Baxter equation, i.e. -matrix. For 2-body interaction, gives the “superconducting” chain that is the same as 1D Kitaev chain model. The 3-body Hamiltonian commuting with Γ is derived by 3-body -matrix, we thus show that the essence of the doubling degeneracy is due to . We also show that the extended Γ′-operator is an invariant of braid group BN for odd N. Moreover, with the extended Γ′-operator, we construct the high dimensional matrix representation of solution to Yang-Baxter equation and find its application in constructing 2N-qubit Greenberger-Horne-Zeilinger state for odd N. PMID:25631987
The MAJORANA DEMONSTRATOR for 0νββ: Current Status and Future Plans
Green, M. P.; Abgrall, N.; Aguayo, Estanislao; Avignone, Frank T.; Barabash, Alexander; Bertrand, F.; Boswell, M.; Brudanin, V.; Busch, Matthew; Byram, D.; Caldwell, A. S.; Chan, Yuen-Dat; Christofferson, Cabot-Ann; Combs, Dustin C.; Cuesta, C.; Detwiler, Jason A.; Doe, P. J.; Efremenko, Yuri; Egorov, Viatcheslav; Ejiri, H.; Elliott, S. R.; Fast, James E.; Finnerty, P.; Fraenkle, Florian; Galindo-Uribarri, A.; Giovanetti, G. K.; Goett, J.; Gruszko, J.; Guiseppe, Vincente; Gusev, K.; Hallin, A. L.; Hazama, R.; Hegai, A.; Henning, Reyco; Hoppe, Eric W.; Howard, Stanley; Howe, M. A.; Keeter, K.; Kidd, M. F.; Kochetov, Oleg; Konovalov, S.; Kouzes, Richard T.; Laferriere, Brian D.; Leon, Jonathan D.; Leviner, L.; Loach, J. C.; MacMullin, J.; MacMullin, S.; Martin, R. D.; Meijer, S. J.; Mertens, S.; Nomachi, Masaharu; Orrell, John L.; O'Shaughnessy, Mark D.; Overman, Nicole R.; Phillips, David; Poon, Alan; Pushkin, K.; Radford, D. C.; Rager, J.; Rielage, Keith; Robertson, R. G. H.; Romero-Romero, E.; Ronquest, M. C.; Schubert, Alexis G.; Shanks, B.; Shima, T.; Shirchenko, M.; Snavely, Kyle J.; Snyder, N.; Suriano, Anne-Marie; Thompson, J.; Timkin, V.; Tornow, Werner; Trimble, J. E.; Varner, R. L.; Vasilyev, Sergey; Vetter, Kai; Vorren, Kris R.; White, Brandon R.; Wilkerson, J. F.; Wiseman, C.; Xu, W.; Yakushev, E.; Young, A.; Yu, Chang-Hong; Yumatov, Vladimir
2015-03-24
The Majorana Demonstrator will search for neutrinoless-double-beta decay in 76Ge, while establishing the feasibility of a future tonne-scale germanium-based neutrinoless-double-beta decay experiment, and performing searches for new physics beyond the Standard Model. The experiment, currently under construction at the Sanford Underground Research Facility in Lead, SD, will consist of a pair of modular high-purity germanium detector arrays housed inside of a compact copper, lead, and polyethylene shield. Through a combination of strict materials qualifications and assay, low-background design, and powerful background rejection techniques, the Demonstrator aims to achieve a background rate in the neutrinoless-double-beta decay region of interest (ROI) of no more than 3cnts/(ROI-t-y). The current status of the Demonstrator is discussed, as are plans for its completion.
The MAJORANA DEMONSTRATOR for 0νββ: Current status and future plans
Green, M. P.; Abgrall, N.; Aguayo, E.; Avignone, III, F. T.; Barabash, A. S.; Bertrand, F. E.; Boswell, M.; Brudanin, V.; Busch, M.; Byram, D.; Caldwell, A. S.; Chan, Y. -D.; Christofferson, C. D.; Combs, D. C.; Cuesta, C.; Detwiler, J. A.; Doe, P. J.; Efremenko, Yu.; Egorov, V.; Ejiri, H.; Elliott, S. R.; Fast, J. E.; Finnerty, P.; Fraenkle, F. M.; Galindo-Uribarri, A.; Giovanetti, G. K.; Goett, J.; Gruszko, J.; Guiseppe, V. E.; Gusev, K.; Hallin, A. L.; Hazama, R.; Hegai, A.; Henning, R.; Hoppe, E. W.; Howard, S.; Howe, M. A.; Keeter, K. J.; Kidd, M. F.; Kochetov, O.; Konovalov, S. I.; Kouzes, R. T.; LaFerriere, B. D.; Leon, J.; Leviner, L. E.; Loach, J. C.; MacMullin, J.; MacMullin, S.; Martin, R. D.; Meijer, S.; Mertens, S.; Nomachi, M.; Orrell, J. L.; O'Shaughnessy, C.; Overman, N. R.; Phillips, II, D. G.; Poon, A. W.P.; Pushkin, K.; Radford, D. C.; Rager, J.; Rielage, K.; Robertson, R. G.H.; Romero-Romero, E.; Ronquest, M. C.; Schubert, A. G.; Shanks, B.; Shima, T.; Shirchenko, M.; Snavely, K. J.; Snyder, N.; Suriano, A. M.; Thompson, J.; Timkin, V.; Tornow, W.; Trimble, J. E.; Varner, R. L.; Vasilyev, S.; Vetter, K.; Vorren, K.; White, B. R.; Wilkerson, J. F.; Wiseman, C.; Xu, W.; Yakushev, E.; Young, A. R.; Yu, C. -H.; Yumatov, V.
2015-01-01
The Majorana Demonstrator will search for neutrinoless-double-beta decay (0νββ) in 76Ge, while establishing the feasibility of a future tonne-scale germanium-based 0νββ experiment, and performing searches for new physics beyond the Standard Model. The experiment, currently under construction at the Sanford Underground Research Facility in Lead, SD, will consist of a pair of modular high-purity germanium detector arrays housed inside of a compact copper, lead, and polyethylene shield. Through a combination of strict materials qualifications and assay, low-background design, and powerful background rejection techniques, the Demonstrator aims to achieve a background rate in the 0νββ region of interest (ROI) of no more than 3 counts in the 0νββ-decay ROI per tonne of target isotope per year (cnts/(ROI-t-y)). The current status of the Demonstrator is discussed, as are plans for its completion.
Search for Majorana Neutrinos Near the Inverted Mass Hierarchy Region with KamLAND-Zen
NASA Astrophysics Data System (ADS)
Gando, A.; Gando, Y.; Hachiya, T.; Hayashi, A.; Hayashida, S.; Ikeda, H.; Inoue, K.; Ishidoshiro, K.; Karino, Y.; Koga, M.; Matsuda, S.; Mitsui, T.; Nakamura, K.; Obara, S.; Oura, T.; Ozaki, H.; Shimizu, I.; Shirahata, Y.; Shirai, J.; Suzuki, A.; Takai, T.; Tamae, K.; Teraoka, Y.; Ueshima, K.; Watanabe, H.; Kozlov, A.; Takemoto, Y.; Yoshida, S.; Fushimi, K.; Banks, T. I.; Berger, B. E.; Fujikawa, B. K.; O'Donnell, T.; Winslow, L. A.; Efremenko, Y.; Karwowski, H. J.; Markoff, D. M.; Tornow, W.; Detwiler, J. A.; Enomoto, S.; Decowski, M. P.; KamLAND-Zen Collaboration
2016-08-01
We present an improved search for neutrinoless double-beta (0 ν β β ) decay of 136Xe in the KamLAND-Zen experiment. Owing to purification of the xenon-loaded liquid scintillator, we achieved a significant reduction of the Agm110 contaminant identified in previous searches. Combining the results from the first and second phase, we obtain a lower limit for the 0 ν β β decay half-life of T1/2 0 ν>1.07 ×1 026 yr at 90% C.L., an almost sixfold improvement over previous limits. Using commonly adopted nuclear matrix element calculations, the corresponding upper limits on the effective Majorana neutrino mass are in the range 61-165 meV. For the most optimistic nuclear matrix elements, this limit reaches the bottom of the quasidegenerate neutrino mass region.
Majorana bound state in a coupled quantum-dot hybrid-nanowire system
NASA Astrophysics Data System (ADS)
Deng, M. T.; Vaitiekėnas, S.; Hansen, E. B.; Danon, J.; Leijnse, M.; Flensberg, K.; Nygård, J.; Krogstrup, P.; Marcus, C. M.
2016-12-01
Hybrid nanowires combining semiconductor and superconductor materials appear well suited for the creation, detection, and control of Majorana bound states (MBSs). We demonstrate the emergence of MBSs from coalescing Andreev bound states (ABSs) in a hybrid InAs nanowire with epitaxial Al, using a quantum dot at the end of the nanowire as a spectrometer. Electrostatic gating tuned the nanowire density to a regime of one or a few ABSs. In an applied axial magnetic field, a topological phase emerges in which ABSs move to zero energy and remain there, forming MBSs. We observed hybridization of the MBS with the end-dot bound state, which is in agreement with a numerical model. The ABS/MBS spectra provide parameters that are useful for understanding topological superconductivity in this system.
NASA Astrophysics Data System (ADS)
Yu, Li-Wei; Ge, Mo-Lin
2015-01-01
A new realization of doubling degeneracy based on emergent Majorana operator Γ presented by Lee-Wilczek has been made. The Hamiltonian can be obtained through the new type of solution of Yang-Baxter equation, i.e. -matrix. For 2-body interaction, gives the ``superconducting'' chain that is the same as 1D Kitaev chain model. The 3-body Hamiltonian commuting with Γ is derived by 3-body -matrix, we thus show that the essence of the doubling degeneracy is due to . We also show that the extended Γ'-operator is an invariant of braid group BN for odd N. Moreover, with the extended Γ'-operator, we construct the high dimensional matrix representation of solution to Yang-Baxter equation and find its application in constructing 2N-qubit Greenberger-Horne-Zeilinger state for odd N.
Search for Majorana Neutrinos Near the Inverted Mass Hierarchy Region with KamLAND-Zen.
Gando, A; Gando, Y; Hachiya, T; Hayashi, A; Hayashida, S; Ikeda, H; Inoue, K; Ishidoshiro, K; Karino, Y; Koga, M; Matsuda, S; Mitsui, T; Nakamura, K; Obara, S; Oura, T; Ozaki, H; Shimizu, I; Shirahata, Y; Shirai, J; Suzuki, A; Takai, T; Tamae, K; Teraoka, Y; Ueshima, K; Watanabe, H; Kozlov, A; Takemoto, Y; Yoshida, S; Fushimi, K; Banks, T I; Berger, B E; Fujikawa, B K; O'Donnell, T; Winslow, L A; Efremenko, Y; Karwowski, H J; Markoff, D M; Tornow, W; Detwiler, J A; Enomoto, S; Decowski, M P
2016-08-19
We present an improved search for neutrinoless double-beta (0νββ) decay of ^{136}Xe in the KamLAND-Zen experiment. Owing to purification of the xenon-loaded liquid scintillator, we achieved a significant reduction of the ^{110m}Ag contaminant identified in previous searches. Combining the results from the first and second phase, we obtain a lower limit for the 0νββ decay half-life of T_{1/2}^{0ν}>1.07×10^{26} yr at 90% C.L., an almost sixfold improvement over previous limits. Using commonly adopted nuclear matrix element calculations, the corresponding upper limits on the effective Majorana neutrino mass are in the range 61-165 meV. For the most optimistic nuclear matrix elements, this limit reaches the bottom of the quasidegenerate neutrino mass region.
Search for Majorana neutrinos in B- → π+ μ- μ- decays.
Aaij, R; Adeva, B; Adinolfi, M; Affolder, A; Ajaltouni, Z; Albrecht, J; Alessio, F; Alexander, M; Ali, S; Alkhazov, G; Alvarez Cartelle, P; Alves, A A; Amato, S; Amerio, S; Amhis, Y; Anderlini, L; Anderson, J; Andreassen, R; Andreotti, M; Andrews, J E; Appleby, R B; Aquines Gutierrez, O; Archilli, F; Artamonov, A; Artuso, M; Aslanides, E; Auriemma, G; Baalouch, M; Bachmann, S; Back, J J; Badalov, A; Balagura, V; Baldini, W; Barlow, R J; Barschel, C; Barsuk, S; Barter, W; Batozskaya, V; Bauer, T; Bay, A; Beddow, J; Bedeschi, F; Bediaga, I; Belogurov, S; Belous, K; Belyaev, I; Ben-Haim, E; Bencivenni, G; Benson, S; Benton, J; Berezhnoy, A; Bernet, R; Bettler, M-O; van Beuzekom, M; Bien, A; Bifani, S; Bird, T; Bizzeti, A; Bjørnstad, P M; Blake, T; Blanc, F; Blouw, J; Blusk, S; Bocci, V; Bondar, A; Bondar, N; Bonivento, W; Borghi, S; Borgia, A; Borsato, M; Bowcock, T J V; Bowen, E; Bozzi, C; Brambach, T; van den Brand, J; Bressieux, J; Brett, D; Britsch, M; Britton, T; Brook, N H; Brown, H; Bursche, A; Busetto, G; Buytaert, J; Cadeddu, S; Calabrese, R; Callot, O; Calvi, M; Calvo Gomez, M; Camboni, A; Campana, P; Campora Perez, D; Carbone, A; Carboni, G; Cardinale, R; Cardini, A; Carranza-Mejia, H; Carson, L; Carvalho Akiba, K; Casse, G; Castillo Garcia, L; Cattaneo, M; Cauet, C; Cenci, R; Charles, M; Charpentier, P; Cheung, S-F; Chiapolini, N; Chrzaszcz, M; Ciba, K; Cid Vidal, X; Ciezarek, G; Clarke, P E L; Clemencic, M; Cliff, H V; Closier, J; Coca, C; Coco, V; Cogan, J; Cogneras, E; Collins, P; Comerma-Montells, A; Contu, A; Cook, A; Coombes, M; Coquereau, S; Corti, G; Counts, I; Couturier, B; Cowan, G A; Craik, D C; Cruz Torres, M; Cunliffe, S; Currie, R; D'Ambrosio, C; Dalseno, J; David, P; David, P N Y; Davis, A; De Bonis, I; De Bruyn, K; De Capua, S; De Cian, M; De Miranda, J M; De Paula, L; De Silva, W; De Simone, P; Decamp, D; Deckenhoff, M; Del Buono, L; Déléage, N; Derkach, D; Deschamps, O; Dettori, F; Di Canto, A; Dijkstra, H; Donleavy, S; Dordei, F; Dorigo, M; Dorosz, P; Dosil Suárez, A; Dossett, D; Dovbnya, A; Dupertuis, F; Durante, P; Dzhelyadin, R; Dziurda, A; Dzyuba, A; Easo, S; Egede, U; Egorychev, V; Eidelman, S; Eisenhardt, S; Eitschberger, U; Ekelhof, R; Eklund, L; El Rifai, I; Elsasser, C; Falabella, A; Färber, C; Farinelli, C; Farry, S; Ferguson, D; Fernandez Albor, V; Ferreira Rodrigues, F; Ferro-Luzzi, M; Filippov, S; Fiore, M; Fiorini, M; Fitzpatrick, C; Fontana, M; Fontanelli, F; Forty, R; Francisco, O; Frank, M; Frei, C; Frosini, M; Furfaro, E; Gallas Torreira, A; Galli, D; Gandelman, M; Gandini, P; Gao, Y; Garofoli, J; Garra Tico, J; Garrido, L; Gaspar, C; Gauld, R; Gersabeck, E; Gersabeck, M; Gershon, T; Ghez, P; Gianelle, A; Gibson, V; Giubega, L; Gligorov, V V; Göbel, C; Golubkov, D; Golutvin, A; Gomes, A; Gordon, H; Grabalosa Gándara, M; Graciani Diaz, R; Granado Cardoso, L A; Graugés, E; Graziani, G; Grecu, A; Greening, E; Gregson, S; Griffith, P; Grillo, L; Grünberg, O; Gui, B; Gushchin, E; Guz, Y; Gys, T; Hadjivasiliou, C; Haefeli, G; Haen, C; Hafkenscheid, T W; Haines, S C; Hall, S; Hamilton, B; Hampson, T; Hansmann-Menzemer, S; Harnew, N; Harnew, S T; Harrison, J; Hartmann, T; He, J; Head, T; Heijne, V; Hennessy, K; Henrard, P; Hernando Morata, J A; van Herwijnen, E; Heß, M; Hicheur, A; Hill, D; Hoballah, M; Hombach, C; Hulsbergen, W; Hunt, P; Huse, T; Hussain, N; Hutchcroft, D; Hynds, D; Iakovenko, V; Idzik, M; Ilten, P; Jacobsson, R; Jaeger, A; Jans, E; Jaton, P; Jawahery, A; Jing, F; John, M; Johnson, D; Jones, C R; Joram, C; Jost, B; Jurik, N; Kaballo, M; Kandybei, S; Kanso, W; Karacson, M; Karbach, T M; Kenyon, I R; Ketel, T; Khanji, B; Khurewathanakul, C; Klaver, S; Kochebina, O; Komarov, I; Koopman, R F; Koppenburg, P; Korolev, M; Kozlinskiy, A; Kravchuk, L; Kreplin, K; Kreps, M; Krocker, G; Krokovny, P; Kruse, F; Kucharczyk, M; Kudryavtsev, V; Kurek, K; Kvaratskheliya, T; La Thi, V N; Lacarrere, D; Lafferty, G; Lai, A; Lambert, D; Lambert, R W; Lanciotti, E; Lanfranchi, G; Langenbruch, C; Latham, T; Lazzeroni, C; Le Gac, R; van Leerdam, J; Lees, J-P; Lefèvre, R; Leflat, A; Lefrançois, J; Leo, S; Leroy, O; Lesiak, T; Leverington, B; Li, Y; Liles, M; Lindner, R; Linn, C; Lionetto, F; Liu, B; Liu, G; Lohn, S; Longstaff, I; Lopes, J H; Lopez-March, N; Lowdon, P; Lu, H; Lucchesi, D; Luisier, J; Luo, H; Luppi, E; Lupton, O; Machefert, F; Machikhiliyan, I V; Maciuc, F; Maev, O; Malde, S; Manca, G; Mancinelli, G; Manzali, M; Maratas, J; Marconi, U; Marino, P; Märki, R; Marks, J; Martellotti, G; Martens, A; Martín Sánchez, A; Martinelli, M; Martinez Santos, D; Martins Tostes, D; Massafferri, A; Matev, R; Mathe, Z; Matteuzzi, C; Mazurov, A; McCann, M; McCarthy, J; McNab, A; McNulty, R; McSkelly, B; Meadows, B; Meier, F; Meissner, M; Merk, M; Milanes, D A; Minard, M-N; Molina Rodriguez, J; Monteil, S; Moran, D; Morandin, M; Morawski, P; Mordà, A; Morello, M J; Mountain, R; Mous, I; Muheim, F; Müller, K; Muresan, R; Muryn, B; Muster, B; Naik, P; Nakada, T; Nandakumar, R; Nasteva, I; Needham, M; Neubert, S; Neufeld, N; Nguyen, A D; Nguyen, T D; Nguyen-Mau, C; Nicol, M; Niess, V; Niet, R; Nikitin, N; Nikodem, T; Novoselov, A; Oblakowska-Mucha, A; Obraztsov, V; Oggero, S; Ogilvy, S; Okhrimenko, O; Oldeman, R; Onderwater, G; Orlandea, M; Otalora Goicochea, J M; Owen, P; Oyanguren, A; Pal, B K; Palano, A; Palutan, M; Panman, J; Papanestis, A; Pappagallo, M; Pappalardo, L; Parkes, C; Parkinson, C J; Passaleva, G; Patel, G D; Patel, M; Patrignani, C; Pavel-Nicorescu, C; Pazos Alvarez, A; Pearce, A; Pellegrino, A; Penso, G; Pepe Altarelli, M; Perazzini, S; Perez Trigo, E; Perret, P; Perrin-Terrin, M; Pescatore, L; Pesen, E; Pessina, G; Petridis, K; Petrolini, A; Picatoste Olloqui, E; Pietrzyk, B; Pilař, T; Pinci, D; Pistone, A; Playfer, S; Plo Casasus, M; Polci, F; Polok, G; Poluektov, A; Polycarpo, E; Popov, A; Popov, D; Popovici, B; Potterat, C; Powell, A; Prisciandaro, J; Pritchard, A; Prouve, C; Pugatch, V; Puig Navarro, A; Punzi, G; Qian, W; Rachwal, B; Rademacker, J H; Rakotomiaramanana, B; Rama, M; Rangel, M S; Raniuk, I; Rauschmayr, N; Raven, G; Redford, S; Reichert, S; Reid, M M; dos Reis, A C; Ricciardi, S; Richards, A; Rinnert, K; Rives Molina, V; Roa Romero, D A; Robbe, P; Roberts, D A; Rodrigues, A B; Rodrigues, E; Rodriguez Perez, P; Roiser, S; Romanovsky, V; Romero Vidal, A; Rotondo, M; Rouvinet, J; Ruf, T; Ruffini, F; Ruiz, H; Ruiz Valls, P; Sabatino, G; Saborido Silva, J J; Sagidova, N; Sail, P; Saitta, B; Salustino Guimaraes, V; Sanmartin Sedes, B; Santacesaria, R; Santamarina Rios, C; Santovetti, E; Sapunov, M; Sarti, A; Satriano, C; Satta, A; Savrie, M; Savrina, D; Schiller, M; Schindler, H; Schlupp, M; Schmelling, M; Schmidt, B; Schneider, O; Schopper, A; Schune, M-H; Schwemmer, R; Sciascia, B; Sciubba, A; Seco, M; Semennikov, A; Senderowska, K; Sepp, I; Serra, N; Serrano, J; Seyfert, P; Shapkin, M; Shapoval, I; Shcheglov, Y; Shears, T; Shekhtman, L; Shevchenko, O; Shevchenko, V; Shires, A; Silva Coutinho, R; Simi, G; Sirendi, M; Skidmore, N; Skwarnicki, T; Smith, N A; Smith, E; Smith, E; Smith, J; Smith, M; Snoek, H; Sokoloff, M D; Soler, F J P; Soomro, F; Souza, D; Souza De Paula, B; Spaan, B; Sparkes, A; Spinella, F; Spradlin, P; Stagni, F; Stahl, S; Steinkamp, O; Stevenson, S; Stoica, S; Stone, S; Storaci, B; Stracka, S; Straticiuc, M; Straumann, U; Stroili, R; Subbiah, V K; Sun, L; Sutcliffe, W; Swientek, S; Syropoulos, V; Szczekowski, M; Szczypka, P; Szilard, D; Szumlak, T; T'Jampens, S; Teklishyn, M; Tellarini, G; Teodorescu, E; Teubert, F; Thomas, C; Thomas, E; van Tilburg, J; Tisserand, V; Tobin, M; Tolk, S; Tomassetti, L; Tonelli, D; Topp-Joergensen, S; Torr, N; Tournefier, E; Tourneur, S; Tran, M T; Tresch, M; Tsaregorodtsev, A; Tsopelas, P; Tuning, N; Ubeda Garcia, M; Ukleja, A; Ustyuzhanin, A; Uwer, U; Vagnoni, V; Valenti, G; Vallier, A; Vazquez Gomez, R; Vazquez Regueiro, P; Vázquez Sierra, C; Vecchi, S; Velthuis, J J; Veltri, M; Veneziano, G; Vesterinen, M; Viaud, B; Vieira, D; Vilasis-Cardona, X; Vollhardt, A; Volyanskyy, D; Voong, D; Vorobyev, A; Vorobyev, V; Voß, C; Voss, H; de Vries, J A; Waldi, R; Wallace, C; Wallace, R; Wandernoth, S; Wang, J; Ward, D R; Watson, N K; Webber, A D; Websdale, D; Whitehead, M; Wicht, J; Wiechczynski, J; Wiedner, D; Wiggers, L; Wilkinson, G; Williams, M P; Williams, M; Wilson, F F; Wimberley, J; Wishahi, J; Wislicki, W; Witek, M; Wormser, G; Wotton, S A; Wright, S; Wu, S; Wyllie, K; Xie, Y; Xing, Z; Yang, Z; Yuan, X; Yushchenko, O; Zangoli, M; Zavertyaev, M; Zhang, F; Zhang, L; Zhang, W C; Zhang, Y; Zhelezov, A; Zhokhov, A; Zhong, L; Zvyagin, A
2014-04-04
A search for heavy Majorana neutrinos produced in the B- → π+ μ- μ- decay mode is performed using 3 fb(-1) of integrated luminosity collected with the LHCb detector in pp collisions at center-of-mass energies of 7 and 8 TeV at the LHC. Neutrinos with masses in the range 250 to 5000 MeV and lifetimes from zero to 1000 ps are probed. In the absence of a signal, upper limits are set on the branching fraction B(B- → π+ μ- μ-) as functions of neutrino mass and lifetime. These limits are on the order of 10(-9) for short neutrino lifetimes of 1 ps or less. Limits are also set on the coupling between the muon and a possible fourth-generation neutrino.
NASA Astrophysics Data System (ADS)
Hwang, Myung-Joong; Choi, Mahn-Soo
2013-03-01
We study the effect of ultrastrong cavity-qubit coupling on the low-lying excitations of a chain of coupled circuit quantum electrodynamic (QED) systems. We show that, in the presence of the onsite ultrastrong coupling, the photon hopping between cavities can be mapped to the Ising interaction between the lowest two levels of individual circuit QED of the chain. Based on our mapping, we predict two nearly degenerate ground states whose wave functions involve maximal entanglement between the macroscopic quantum states of the cavities and the states of qubits and identify that they are mathematically equivalent to Majorana bound states. Further, we devise a scheme for the dispersive measurement of the ground states using an additional resonator attached to one end of the circuit QED chain. Finally, we discuss the effects of disorders and local noises on the coherence of the ground states.
Exact classification of Landau-Majorana-Stückelberg-Zener resonances by floquet determinants.
Ganeshan, Sriram; Barnes, Edwin; Das Sarma, S
2013-09-27
Recent experiments have shown that Landau-Majorana-Stückelberg-Zener (LMSZ) interferometry is a powerful tool for demonstrating and exploiting quantum coherence not only in atomic systems but also in a variety of solid state quantum systems such as spins in quantum dots, superconducting qubits, and nitrogen vacancy centers in diamond. In this Letter, we propose and develop a general (and, in principle, exact) theoretical formalism to identify and characterize the interference resonances that are the hallmark of LMSZ interferometry. Unlike earlier approaches, our scheme does not require any approximations, allowing us to uncover important and previously unknown features of the resonance structure. We also discuss the experimental observability of our results.
Coherent Dynamics of Open Quantum System in the Presence of Majorana Fermions
NASA Astrophysics Data System (ADS)
Assuncao, Maryzaura O.; Diniz, Ginetom S.; Vernek, Edson; Souza, Fabricio M.
In recent years the research on quantum coherent dynamics of open systems has attracted great attention due to its relevance for future implementation of quantum computers. In the present study we apply the Kadanoff-Baym formalism to simulate the population dynamics of a double-dot molecular system attached to both a superconductor and fermionic reservoirs. We solve both analytically and numerically a set of coupled differential equations that account for crossed Andreev reflection (CAR), intramolecular hopping and tunneling. We pay particular attention on how Majorana bound states can affect the population dynamics of the molecule. We investigate on how initial state configuration affects the dynamics. For instance, if one dot is occupied and the other one is empty, the dynamics is dictated by the inter dot tunneling. On the other hand, for initially empty dots, the CAR dominates. We also investigate how the source and drain currents evolve in time. This work was supporte by FAPEMIG, CNPq and CAPES.
Localized Majorana-Like Modes in a Number-Conserving Setting: An Exactly Solvable Model.
Iemini, Fernando; Mazza, Leonardo; Rossini, Davide; Fazio, Rosario; Diehl, Sebastian
2015-10-09
In this Letter we present, in a number conserving framework, a model of interacting fermions in a two-wire geometry supporting nonlocal zero-energy Majorana-like edge excitations. The model has an exactly solvable line, on varying the density of fermions, described by a topologically nontrivial ground state wave function. Away from the exactly solvable line we study the system by means of the numerical density matrix renormalization group. We characterize its topological properties through the explicit calculation of a degenerate entanglement spectrum and of the braiding operators which are exponentially localized at the edges. Furthermore, we establish the presence of a gap in its single particle spectrum while the Hamiltonian is gapless, and compute the correlations between the edge modes as well as the superfluid correlations. The topological phase covers a sizable portion of the phase diagram, the solvable line being one of its boundaries.
Cytotoxicity and anti-Sporothrix brasiliensis activity of the Origanum majorana Linn. oil.
Waller, Stefanie Bressan; Madrid, Isabel Martins; Ferraz, Vanny; Picoli, Tony; Cleff, Marlete Brum; de Faria, Renata Osório; Meireles, Mário Carlos Araújo; de Mello, João Roberto Braga
The study aimed to evaluate the anti-Sporothrix sp. activity of the essential oil of Origanum majorana Linn. (marjoram), its chemical analysis, and its cytotoxic activity. A total of 18 fungal isolates of Sporothrix brasiliensis (n: 17) from humans, dogs and cats, and a standard strain of Sporothrix schenckii (n: 1) were tested using the broth microdilution technique (Clinical and Laboratory Standard Institute - CLSI M27-A3) and the results were expressed in minimal inhibitory concentration (MIC) and minimal fungicidal concentration (MFC). The MIC50 and MIC90 of itraconazole against S. brasiliensis were 2μg/mL and 8μg/mL, respectively, and the MFC50 and MFC90 were 2μg/mL and >16μg/mL, respectively, with three S. brasiliensis isolates resistant to antifungal. S. schenckii was sensitive at MIC of 1μg/mL and MFC of 8μg/mL. For the oil of O. majorana L., all isolates were susceptible to MIC of ≤2.25-9mg/mL and MFC of ≤2.25-18mg/mL. The MIC50 and MIC90 were ≤2.25mg/mL and 4.5mg/mL, respectively, and the MFC50/90 values were twice more than the MIC. Twenty-two compounds were identified by gas chromatography with a flame ionization detector (CG-FID) and 1,8-cineole and 4-terpineol were the majority. Through the colorimetric (MTT) assay, the toxicity was observed in 70-80% of VERO cells between 0.078 and 5mg/mL. For the first time, the study demonstrated the satisfactory in vitro anti-Sporothrix sp. activity of marjoram oil and further studies are needed to ensure its safe and effective use.
Search for Majorana neutrinos with the first two years of EXO-200 data
NASA Astrophysics Data System (ADS)
The Exo-200 Collaboration; Albert, J. B.; Auty, D. J.; Barbeau, P. S.; Beauchamp, E.; Beck, D.; Belov, V.; Benitez-Medina, C.; Bonatt, J.; Breidenbach, M.; Brunner, T.; Burenkov, A.; Cao, G. F.; Chambers, C.; Chaves, J.; Cleveland, B.; Coon, M.; Craycraft, A.; Daniels, T.; Danilov, M.; Daugherty, S. J.; Davis, C. G.; Davis, J.; Devoe, R.; Delaquis, S.; Didberidze, T.; Dolgolenko, A.; Dolinski, M. J.; Dunford, M.; Fairbank, W., Jr.; Farine, J.; Feldmeier, W.; Fierlinger, P.; Fudenberg, D.; Giroux, G.; Gornea, R.; Graham, K.; Gratta, G.; Hall, C.; Herrin, S.; Hughes, M.; Jewell, M. J.; Jiang, X. S.; Johnson, A.; Johnson, T. N.; Johnston, S.; Karelin, A.; Kaufman, L. J.; Killick, R.; Koffas, T.; Kravitz, S.; Kuchenkov, A.; Kumar, K. S.; Leonard, D. S.; Leonard, F.; Licciardi, C.; Lin, Y. H.; MacLellan, R.; Marino, M. G.; Mong, B.; Moore, D.; Nelson, R.; Odian, A.; Ostrovskiy, I.; Ouellet, C.; Piepke, A.; Pocar, A.; Prescott, C. Y.; Rivas, A.; Rowson, P. C.; Rozo, M. P.; Russell, J. J.; Schubert, A.; Sinclair, D.; Slutsky, S.; Smith, E.; Stekhanov, V.; Tarka, M.; Tolba, T.; Tosi, D.; Twelker, K.; Vogel, P.; Vuilleumier, J.-L.; Waite, A.; Walton, J.; Walton, T.; Weber, M.; Wen, L. J.; Wichoski, U.; Wright, J. D.; Yang, L.; Yen, Y.-R.; Ya. Zeldovich, O.; Zhao, Y. B.
2014-06-01
Many extensions of the standard model of particle physics suggest that neutrinos should be Majorana-type fermions--that is, that neutrinos are their own anti-particles--but this assumption is difficult to confirm. Observation of neutrinoless double-β decay (0νββ), a spontaneous transition that may occur in several candidate nuclei, would verify the Majorana nature of the neutrino and constrain the absolute scale of the neutrino mass spectrum. Recent searches carried out with 76Ge (the GERDA experiment) and 136Xe (the KamLAND-Zen and EXO (Enriched Xenon Observatory)-200 experiments) have established the lifetime of this decay to be longer than 1025 years, corresponding to a limit on the neutrino mass of 0.2-0.4 electronvolts. Here we report new results from EXO-200 based on a large 136Xe exposure that represents an almost fourfold increase from our earlier published data sets. We have improved the detector resolution and revised the data analysis. The half-life sensitivity we obtain is 1.9 × 1025 years, an improvement by a factor of 2.7 on previous EXO-200 results. We find no statistically significant evidence for 0νββ decay and set a half-life limit of 1.1 × 1025 years at the 90 per cent confidence level. The high sensitivity holds promise for further running of the EXO-200 detector and future 0νββ decay searches with an improved Xe-based experiment, nEXO.
Search for Majorana neutrinos with the first two years of EXO-200 data.
2014-06-12
Many extensions of the standard model of particle physics suggest that neutrinos should be Majorana-type fermions-that is, that neutrinos are their own anti-particles-but this assumption is difficult to confirm. Observation of neutrinoless double-β decay (0νββ), a spontaneous transition that may occur in several candidate nuclei, would verify the Majorana nature of the neutrino and constrain the absolute scale of the neutrino mass spectrum. Recent searches carried out with (76)Ge (the GERDA experiment) and (136)Xe (the KamLAND-Zen and EXO (Enriched Xenon Observatory)-200 experiments) have established the lifetime of this decay to be longer than 10(25) years, corresponding to a limit on the neutrino mass of 0.2-0.4 electronvolts. Here we report new results from EXO-200 based on a large (136)Xe exposure that represents an almost fourfold increase from our earlier published data sets. We have improved the detector resolution and revised the data analysis. The half-life sensitivity we obtain is 1.9 × 10(25) years, an improvement by a factor of 2.7 on previous EXO-200 results. We find no statistically significant evidence for 0νββ decay and set a half-life limit of 1.1 × 10(25) years at the 90 per cent confidence level. The high sensitivity holds promise for further running of the EXO-200 detector and future 0νββ decay searches with an improved Xe-based experiment, nEXO.
Person-centred reflective practice.
Devenny, Bob; Duffy, Kathleen
Person-centred health and person-centred care have gained prominence across the UK following the publication of reports on public inquiries exploring failings in care. Self-awareness and participation in reflective practice are recognised as vital to supporting the person-centred agenda. This article presents an education framework for reflective practice, developed and used in one NHS board in Scotland, and based on the tenets of the clinical pastoral education movement. Providing an insight into the usefulness of a spiritual component in the reflective process, the framework provides an opportunity for nurses and other healthcare professionals to examine the spiritual dimensions of patient encounters, their own values and beliefs, and the effect these may have on their practice.
Li, Ying
2016-09-16
Fault-tolerant quantum computing in systems composed of both Majorana fermions and topologically unprotected quantum systems, e.g., superconducting circuits or quantum dots, is studied in this Letter. Errors caused by topologically unprotected quantum systems need to be corrected with error-correction schemes, for instance, the surface code. We find that the error-correction performance of such a hybrid topological quantum computer is not superior to a normal quantum computer unless the topological charge of Majorana fermions is insusceptible to noise. If errors changing the topological charge are rare, the fault-tolerance threshold is much higher than the threshold of a normal quantum computer and a surface-code logical qubit could be encoded in only tens of topological qubits instead of about 1,000 normal qubits.
NASA Astrophysics Data System (ADS)
Venderbos, Jörn W. F.; Kozii, Vladyslav; Fu, Liang
2016-11-01
Motivated by the recent experiment indicating that superconductivity in the doped topological insulator CuxBi2Se3 has an odd-parity pairing symmetry with rotational symmetry breaking, we study the general class of odd-parity superconductors with two-component order parameters in trigonal and hexagonal crystal systems. In the presence of strong spin-orbit interaction, we find two possible superconducting phases below Tc, a time-reversal-breaking (i.e., chiral) phase and an anisotropic (i.e., nematic) phase, and determine their relative energetics from the gap function in momentum space. The nematic superconductor generally has a full quasiparticle gap, whereas the chiral superconductor with a three-dimensional (3D) Fermi surface has point nodes with lifted spin degeneracy, resulting in itinerant Majorana fermions in the bulk and topological Majorana arcs on the surface.
InSb Nanowires with Built-In GaxIn1-xSb Tunnel Barriers for Majorana Devices.
Car, Diana; Conesa-Boj, Sonia; Zhang, Hao; Op Het Veld, Roy L M; de Moor, Michiel W A; Fadaly, Elham M T; Gül, Önder; Kölling, Sebastian; Plissard, Sebastien R; Toresen, Vigdis; Wimmer, Michael T; Watanabe, Kenji; Taniguchi, Takashi; Kouwenhoven, Leo P; Bakkers, Erik P A M
2017-02-08
Majorana zero modes (MZMs), prime candidates for topological quantum bits, are detected as zero bias conductance peaks (ZBPs) in tunneling spectroscopy measurements. Implementation of a narrow and high tunnel barrier in the next generation of Majorana devices can help to achieve the theoretically predicted quantized height of the ZBP. We propose a material-oriented approach to engineer a sharp and narrow tunnel barrier by synthesizing a thin axial segment of GaxIn1-xSb within an InSb nanowire. By varying the precursor molar fraction and the growth time, we accurately control the composition and the length of the barriers. The height and the width of the GaxIn1-xSb tunnel barrier are extracted from the Wentzel-Kramers-Brillouin (WKB) fits to the experimental I-V traces.
Hsieh, Timothy H; Fu, Liang
2012-03-09
The recently discovered superconductor Cu(x)Bi2Se3 is a candidate for three-dimensional time-reversal-invariant topological superconductors, which are predicted to have robust surface Andreev bound states hosting massless Majorana fermions. In this work, we analytically and numerically find the linearly dispersing Majorana fermions at k=0, which smoothly evolve into a new branch of gapless surface Andreev bound states near the Fermi momentum. The latter is a new type of Andreev bound states resulting from both the nontrivial band structure and the odd-parity pairing symmetry. The tunneling spectra of these surface Andreev bound states agree well with a recent point-contact spectroscopy experiment [S. Sasaki et al., Phys. Rev. Lett. 107, 217001 (2011)] and yield additional predictions for low temperature tunneling and photoemission experiments.
Aalseth, Craig E; Amman, M; Amsbaugh, John F; Avignone, F. T.; Back, Henning O; Barabash, A; Barbeau, Phil; Beene, Jim; Bergevin, M; Bertrand, F; Boswell, M; Brudanin, V; Bugg, William; Burritt, Tom H; Chan, Yuen-Dat; Collar, J I; Cooper, R J; Creswick, R; Detwiler, Jason A; Doe, P J; Efremenko, Yuri; Egorov, Viatcheslav; Ejiri, H; Elliott, Steven R; Ely, James H; Esterline, James H; Farach, H A; Fast, James E; Fields, N; Finnerty, P; Fujikawa, Brian; Fuller, Erin S; Gehman, Victor; Giovanetti, G K; Guiseppe, Vincente; Gusey, K; Hallin, A L; Hazama, R; Henning, Reyco; Hime, Andrew; Hoppe, Eric W; Hossbach, Todd W; Howe, M A; Johnson, R A; Keeter, K; Keillor, Martin E; Keller, C; Kephart, Jeremy D; Kidd, Mary; Kochetov, Oleg; Konovalov, S; Kouzes, Richard T; Lesko, Kevin; Leviner, L; Loach, J C; Luke, P; MacMullin, S; Marino, Michael G; Mei, Dong-Ming; Miley, Harry S; Miller, M; Mizouni, Leila K; Montoya, A; Myers, A W; Nomachi, Masaharu; Odom, Brian; Orrell, John L; Phillips, D; Poon, Alan; Prior, Gersende; Qian, J; Radford, D C; Rielage, Keith; Robertson, R G. H.; Rodriguez, Larry; Rykaczewski, Krzysztof P; Schubert, Alexis G; Shima, T; Shirchenko, M; Strain, J; Thomas, K; Thompson, Robert C; Timkin, V; Tornow, W; Van Wechel, T D; Vanyushin, I; Vetter, Kai; Warner, Ray A; Wilkerson, J; Wouters, Jan; Yakushev, E; Young, A; Yu, Chang-Hong; Yumatov, Vladimir; Zhang, C L; Zimmerman, S
2009-12-17
The MAJORANA collaboration is pursuing the development of the so-called MAJORANA DEMONSTRATOR. The DEMONSTRATOR is intended to perform research and development towards a tonne-scale germanium-based experiment to search for the neutrinoless double-beta decay of 76Ge. The DEMONSTRATOR can also perform a competitive direct dark matter search for light WIMPs in the 1-10GeV/c2 mass range. It will consist of approximately 60 kg. of germanium detectors in an ultra-low background shield located deep underground at the Sanford Underground Laboratory in Lead, SD. The DEMONSTRATOR will also perform background and technology studies, and half of the detector mass will be enriched germanium. This talk will review the motivation, design, technology and status of the Demonstrator.
Aalseth, C. E.; Ely, J.; Fast, J. E.; Fuller, E.; Hoppe, E. W.; Keillor, M.; Kouzes, R. T.; Miley, H. S.; Orrell, J. L.; Thompson, R.; Warner, R.; Amman, M.; Bergevin, M.; Chan, Y.-D.; Detwiler, J. A.; Fujikawa, B.; Loach, J. C.; Luke, P. N.; Poon, A. W. P; Prior, G.
2009-12-17
The MAJORANA collaboration is pursuing the development of the so-called MAJORANA DEMONSTRATOR. The DEMONSTRATOR is intended to perform research and development towards a tonne-scale germanium-based experiment to search for the neutrinoless double-beta decay of {sup 76}Ge. The DEMONSTRATOR can also perform a competitive direct dark matter search for light WIMPs in the 1-10 GeV/c{sup 2} mass range. It will consist of approximately 60 kg of germanium detectors in an ultra-low background shield located deep underground at the Sanford Underground Laboratory in Lead, SD. The DEMONSTRATOR will also perform background and technology studies, and half of the detector mass will be enriched germanium. This talk will review the motivation, design, technology and status of the Demonstrator.
Crossover from Majorana edge- to end-states in quasi-one-dimensional p-wave superconductors
NASA Astrophysics Data System (ADS)
Zhou, Bin; Shen, Shun-Qing
2011-08-01
In a recent work [Potter and Lee, Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.105.227003 105, 227003 (2010)], it was demonstrated by means of numerical diagonalization that the Majorana end states can be localized at opposite ends of a sample of an ideal spinless p-wave superconductor with the strip geometry beyond the strict one-dimensional limit. Here, we reexamine this issue and study the topological quantum phase transition in the same system. We give the phase diagrams of the presence of Majorana end modes by using of Z2 topological index. It is found that the topological property of a strip geometry will change in an oscillatory way with respect of the sample width.
NASA Astrophysics Data System (ADS)
Li, Ying
2016-09-01
Fault-tolerant quantum computing in systems composed of both Majorana fermions and topologically unprotected quantum systems, e.g., superconducting circuits or quantum dots, is studied in this Letter. Errors caused by topologically unprotected quantum systems need to be corrected with error-correction schemes, for instance, the surface code. We find that the error-correction performance of such a hybrid topological quantum computer is not superior to a normal quantum computer unless the topological charge of Majorana fermions is insusceptible to noise. If errors changing the topological charge are rare, the fault-tolerance threshold is much higher than the threshold of a normal quantum computer and a surface-code logical qubit could be encoded in only tens of topological qubits instead of about 1,000 normal qubits.
NASA Astrophysics Data System (ADS)
Zhao, Hong-Kang; Zhang, Jian; Wang, Jian
2016-11-01
The dynamic properties of a quantum dot (QD) coupled with Majorana fermions under the perturbation of microwave fields (MWFs) have been investigated through the nonequilibrium Green's function (NGF) technique. The photon-assisted differential conductance, current, shot noise, and Fano factor have been evaluated in the Nambu representation. The normal electron tunneling and Andreev reflections contribute to the transport effectively, and novel conductance peaks appear around each photon-induced side channel. The shot noise is enhanced by increasing the interaction strength of Majorana fermions evidently, while it is suppressed accompanying with peak-valley structures by the MWFs. For the symmetric transmission where the QD energy Ed = 0, terminal current disappears when the source-drain bias eV is removed. For the asymmetric transmission where Ed ≠ 0, there exists nonzero pumping current induced by the applied MWF. The saturate pumping current increases with increasing Ed as eV = 0 and Ed ≠ 0, but the shot noise increases with decreasing Ed. As the coupling energy between the Majorana fermions becomes zero, the Fano factor reaches the robust value F ≈ 0.38 as eV → 0.
NASA Astrophysics Data System (ADS)
Nori, Franco
2012-02-01
This talk will present an overview of some of our recent results on atomic physics and quantum optics using superconducting circuits. Particular emphasis will be given to photons interacting with qubits, interferometry, the Dynamical Casimir effect, and also studying Majorana fermions using superconducting circuits.[4pt] References available online at our web site:[0pt] J.Q. You, Z.D. Wang, W. Zhang, F. Nori, Manipulating and probing Majorana fermions using superconducting circuits, (2011). Arxiv. J.R. Johansson, G. Johansson, C.M. Wilson, F. Nori, Dynamical Casimir effect in a superconducting coplanar waveguide, Phys. Rev. Lett. 103, 147003 (2009). [0pt] J.R. Johansson, G. Johansson, C.M. Wilson, F. Nori, Dynamical Casimir effect in superconducting microwave circuits, Phys. Rev. A 82, 052509 (2010). [0pt] C.M. Wilson, G. Johansson, A. Pourkabirian, J.R. Johansson, T. Duty, F. Nori, P. Delsing, Observation of the Dynamical Casimir Effect in a superconducting circuit. Nature, in press (Nov. 2011). P.D. Nation, J.R. Johansson, M.P. Blencowe, F. Nori, Stimulating uncertainty: Amplifying the quantum vacuum with superconducting circuits, Rev. Mod. Phys., in press (2011). [0pt] J.Q. You, F. Nori, Atomic physics and quantum optics using superconducting circuits, Nature 474, 589 (2011). [0pt] S.N. Shevchenko, S. Ashhab, F. Nori, Landau-Zener-Stuckelberg interferometry, Phys. Reports 492, 1 (2010). [0pt] I. Buluta, S. Ashhab, F. Nori. Natural and artificial atoms for quantum computation, Reports on Progress in Physics 74, 104401 (2011). [0pt] I.Buluta, F. Nori, Quantum Simulators, Science 326, 108 (2009). [0pt] L.F. Wei, K. Maruyama, X.B. Wang, J.Q. You, F. Nori, Testing quantum contextuality with macroscopic superconducting circuits, Phys. Rev. B 81, 174513 (2010). [0pt] J.Q. You, X.-F. Shi, X. Hu, F. Nori, Quantum emulation of a spin system with topologically protected ground states using superconducting quantum circuit, Phys. Rev. A 81, 063823 (2010).
Rapid Service/Prediction Centre
2009-01-01
respect to the 05 C04 system of the IERS Earth Orientation Centre (EOC) at the Paris Observatory by way of a robust linear estimator. Statistical...of each individual data point. The software computes the spline coefficients for every data point, which are then used to interpolate the Earth ...between daily rapid solutions at each daily solution epoch for 2008 and the Earth orientation parameters available in 05 C04 series produced in March 2009
National Centre for Radio Astrophysics
NASA Astrophysics Data System (ADS)
Murdin, P.
2000-11-01
India's National Centre for Radio Astrophysics (NCRA), located on the Pune University Campus, is part of the TATA INSTITUTE OF FUNDAMENTAL RESEARCH. At Khodad, 80 km from Pune, NCRA has set up the Giant Metrewave Radio Telescope (GMRT), the world's largest telescope operating at meter wavelengths. GMRT consists of 30 fully steerable dishes of 45 m diameter, spread over a 25 km area. Another meter...
European Centre for Disease Prevention and Control.
Evans, Roger
2014-11-04
The European Centre for Disease Prevention and Control was set up in 2005 to strengthen Europe's defences against infectious diseases. The centre is an independent agency of the European Union and is based in Stockholm, Sweden.
NASA Astrophysics Data System (ADS)
Huang, Guang-Yao; Leijnse, Martin; Flensberg, Karsten; Xu, H. Q.
2014-12-01
We theoretically investigate electronic transport through a junction where a quantum dot (QD) is tunnel coupled on both sides to semiconductor nanowires with strong spin-orbit interaction and proximity-induced superconductivity. The results are presented as stability diagrams, i.e., the differential conductance as a function of the bias voltage applied across the junction and the gate voltage used to control the electrostatic potential on the QD. A small applied magnetic field splits and modifies the resonances due to the Zeeman splitting of the QD level. Above a critical field strength, Majorana bound states (MBS) appear at the interfaces between the two superconducting nanowires and the QD, resulting in a qualitative change of the entire stability diagram, suggesting this setup as a promising platform to identify MBS. Our calculations are based on a nonequilibrium Green's function description and is exact when Coulomb interactions on the QD can be neglected. In addition, we develop a simple pictorial view of the involved transport processes, which is equivalent to a description in terms of multiple Andreev reflections, but provides an alternative way to understand the role of the QD level in enhancing transport for certain gate and bias voltages. We believe that this description will be useful in future studies of interacting QDs coupled to superconducting leads (with or without MBS), where it can be used to develop a perturbation expansion in the tunnel coupling.
Josephson current in finite-lenght nanowire SNS junctions with Majorana fermions
NASA Astrophysics Data System (ADS)
Aguado, Ramon; Prada, Elsa; San Jose, Pablo
2012-02-01
The dc Josephson effect (JE) through infinite-lenght junctions of one-dimensional topological superconductors exhibits an anomalous 4π periodic phase (φ) dependence which originates from a parity-protected level crossing of zero-energy Majorana bound states (MBS) at φ=π. This ``fractional'' JE provides an important experimental detection tool for MBS. In this talk, I will discuss the JE in more realistic SNS junctions of arbitrary transparency and when both the normal and the nanowire regions are of finite length, namely beyond the short-junction and infinite topological superconductor limits. In general, the spectrum of Andreev bound states can become rather intricate and dense as opposed to the infinite-lenght case. Moreover, the low-energy spectrum around φ=π shows always anticrossings, originated from hybridization of four MBS, which may preclude the experimental observation of the fractional JE. At finite bias voltages, Landau-Zener dynamics involving the MBS and quasi-continuum Andreev levels gives rise to a nontrivial ac Josephson current. Interestingly, the ac current phase diagram as a function of the Josephson frequency/normal transmission shows fractional JE regions which are tunable through bias/gate voltages.
Fermionic and Majorana bound states in hybrid nanowires with non-uniform spin-orbit interaction
NASA Astrophysics Data System (ADS)
Klinovaja, Jelena; Loss, Daniel
2015-03-01
We study intragap bound states in the topological phase of a Rashba nanowire in the presence of a magnetic field and with non-uniform spin orbit interaction (SOI) and proximity-induced superconductivity gap. We show that fermionic bound states (FBS) can emerge inside the proximity gap. They are localized at the junction between two wire sections characterized by different directions of the SOI vectors, and they coexist with Majorana bound states (MBS) localized at the nanowire ends. The energy of the FBS is determined by the angle between the SOI vectors and the lengthscale over which the SOI changes compared to the Fermi wavelength and the localization length. We also consider double-junctions and show that the two emerging FBSs can hybridize and form a double quantum dot-like structure inside the gap. We find explicit analytical solutions of the bound states and their energies for certain parameter regimes such as weak and strong SOI. The analytical results are confirmed and complemented by an independent numerical tight-binding model approach. Such FBS can act as quasiparticle traps and thus can have implications for topological quantum computing schemes based on braiding MBSs.
Probing Majorana bound states via counting statistics of a single electron transistor
NASA Astrophysics Data System (ADS)
Li, Zeng-Zhao; Lam, Chi-Hang; You, J. Q.
2015-06-01
We propose an approach for probing Majorana bound states (MBSs) in a nanowire via counting statistics of a nearby charge detector in the form of a single-electron transistor (SET). We consider the impacts on the counting statistics by both the local coupling between the detector and an adjacent MBS at one end of a nanowire and the nonlocal coupling to the MBS at the other end. We show that the Fano factor and the skewness of the SET current are minimized for a symmetric SET configuration in the absence of the MBSs or when coupled to a fermionic state. However, the minimum points of operation are shifted appreciably in the presence of the MBSs to asymmetric SET configurations with a higher tunnel rate at the drain than at the source. This feature persists even when varying the nonlocal coupling and the pairing energy between the two MBSs. We expect that these MBS-induced shifts can be measured experimentally with available technologies and can serve as important signatures of the MBSs.
The MAJORANA DEMONSTRATOR for 0νββ: Current status and future plans
Green, M. P.; Abgrall, N.; Aguayo, E.; ...
2015-01-01
The Majorana Demonstrator will search for neutrinoless-double-beta decay (0νββ) in 76Ge, while establishing the feasibility of a future tonne-scale germanium-based 0νββ experiment, and performing searches for new physics beyond the Standard Model. The experiment, currently under construction at the Sanford Underground Research Facility in Lead, SD, will consist of a pair of modular high-purity germanium detector arrays housed inside of a compact copper, lead, and polyethylene shield. Through a combination of strict materials qualifications and assay, low-background design, and powerful background rejection techniques, the Demonstrator aims to achieve a background rate in the 0νββ region of interest (ROI) of nomore » more than 3 counts in the 0νββ-decay ROI per tonne of target isotope per year (cnts/(ROI-t-y)). The current status of the Demonstrator is discussed, as are plans for its completion.« less
Clues on the Majorana scale from scalar resonances at the LHC
NASA Astrophysics Data System (ADS)
Fischer, Oliver
2017-02-01
In order to address the observation of the neutrino oscillations and the metastability of the Standard Model (SM), we extend the fermion sector with two right-handed (i.e. sterile) neutrinos, and the scalar sector of the SM with a real scalar, the Hill field. The latter takes the role of a Majoron and generates the Majorana masses for the neutrino sector, such that the particle spectrum features two CP-even scalars h1 and h2, and also two heavy, mass degenerate neutrinos. When the h1 is identified with the scalar resonance at ˜ 125 GeV and the condition is imposed that the h1 self-coupling and its running vanish at the Planck scale, the scalar mixing and the vacuum expectation value of the Hill field are fixed by the h2 mass. The h2 can be searched for at the LHC, and it has prospects of being discovered for the target integrated luminosities of the HL-LHC and the Future Circular hadron Collider (FCC-hh) when its mass is on the weak scale. The knowledge of the h2 mass and its decay properties can yield an insight into its coupling to the heavy neutrinos, and thus also on the heavy neutrino mass scale. This yields an interesting connection between potentially detectable heavy scalars in high-energy proton collisions and the mass scale of the heavy neutrinos that is testable at the LHC and at future colliders.
Noise Performance Evaluation of the Candidate Digitizers for the MAJORANA DEMONSTRATOR
Aguayo Navarrete, Estanislao
2011-03-16
The noise performance evaluation of the two digitizer cards being considered for the MAJORANA DEMONSTRATOR (MJD) is presented in this document. The procurement of the data acquisition electronics for the MJD is scheduled to happen this year. At the time of writing this document, there are two candidate digitizer electronic boards. One aspect that is being considered by the collaboration is the feasibility of using the MJD for dark matter searches. The feasibility of using the MJD for this application is going to be dictated by the ability of the demonstrator to reach sub-keV energy resolution. One of the potential sources of noise in the MJD is the data acquisition system. This document will is concluded with a recommendation for the final digitizer board by comparing the noise performance of the two electronics systems. Noise parameters such as the effective number of bits, input range linearity and signal to noise ratio are experimentally determined. The two digitizer cards feature different on-board digital signal processing and these features are compared. The experimental set-up was also used to identify sources of noise. This paper describes these sources of noise in the data acquisition system, along with mitigation strategies. Issues such as grounding and wiring scheme have an impact in the overall data acquisition system performance and are discussed in detail. As a conclusion, the suitability of each one of the cards to become the back bone of the data acquisition system of the MJD is discussed.
Index theorem and Majorana zero modes along a non-Abelian vortex in a color superconductor
Fujiwara, Takanori; Fukui, Takahiro; Nitta, Muneto; Yasui, Shigehiro
2011-10-01
Color superconductivity in high-density QCD exhibits the color-flavor-locked phase. To explore zero modes in the color-flavor-locked phase in the presence of a non-Abelian vortex with an SU(2) symmetry in the vortex core, we apply the index theorem to the Bogoliubov-de Gennes (BdG) Hamiltonian. From the calculation of the topological index, we find that triplet, doublet and singlet sectors of SU(2) have certain number of chiral Majorana zero modes in the limit of vanishing chemical potential. We also solve the BdG equation by the use of the series expansion to show that the number of zero modes and their chirality match the result of the index theorem. From particle-hole symmetry of the BdG Hamiltonian, we conclude that if and only if the index of a given sector is odd, one zero mode survives generically for a finite chemical potential. We argue that this result should hold nonperturbatively even in the high-density limit.
The contribution of light Majorana neutrinos to neutrinoless double beta decay and cosmology
Dell’Oro, S.; Marcocci, S.; Viel, M.; Vissani, F.
2015-12-11
Cosmology is making impressive progress and it is producing stringent bounds on the sum of the neutrino masses Σ, a parameter of great importance for the current laboratory experiments. In this letter, we exploit the potential relevance of the analysis of Palanque-Delabrouille et al. to the neutrinoless double beta decay (0νββ) search. This analysis indicates small values for the lightest neutrino mass, since the authors find Σ<84 meV at 1σ C.L., and provides a 1σ preference for the normal hierarchy. The allowed values for the Majorana effective mass, probed by 0νββ, turn out to be <75 meV at 3σ C.L. and lower down to less than 20 meV at 1σ C.L. . If this indication is confirmed, the impact on the 0νββ experiments will be tremendous since the possibility of detecting a signal will be out of the reach of the next generation of experiments.
The
NASA Astrophysics Data System (ADS)
Massarczyk, Ralph; Majorana Collaboration
2016-03-01
Neutrinoless double beta decay searches play a major role in determining neutrino properties. The
Reprint of : Majorana fermion fingerprints in spin-polarised scanning tunnelling microscopy
NASA Astrophysics Data System (ADS)
Kotetes, Panagiotis; Mendler, Daniel; Heimes, Andreas; Schön, Gerd
2016-08-01
We calculate the spatially resolved tunnelling conductance of topological superconductors (TSCs) based on ferromagnetic chains, measured by means of spin-polarised scanning tunnelling microscopy (SPSTM). Our analysis reveals novel signatures of MFs arising from the interplay of their strongly anisotropic spin-polarisation and the magnetisation content of the tip. We focus on the deep Yu-Shiba-Rusinov (YSR) limit where only YSR bound states localised in the vicinity of the adatoms govern the low-energy as also the topological properties of the system. Under these conditions, we investigate the occurrence of zero/finite bias peaks (ZBPs/FBPs) for a single or two coupled TSC chains forming a Josephson junction. Each TSC can host up to two Majorana fermions (MFs) per edge if chiral symmetry is preserved. Here we retrieve the conductance for all the accessible configurations of the MF number of each chain. Our results illustrate innovative spin-polarisation-sensitive experimental routes for arresting the MFs by either restoring or splitting the ZBP in a predictable fashion via: (i) weakly breaking chiral symmetry, e.g. by the SPSTM tip itself or by an external Zeeman field and (ii) tuning the superconducting phase difference of the TSCs, which is encoded in the 4π-Josephson coupling of neighbouring MFs.
Soliman, Amel M.; Desouky, Shreen; Marzouk, Mohamed; Sayed, Amany A.
2016-01-01
Despite the fact that cisplatin is an important anticancer drug, its clinical utilization is limited by nephrotoxicity during long term medication. Combined cisplatin chemotherapy with plant extracts can diminish toxicity and enhance the antitumor efficacy of the drug. This study evaluated the effect of Originum majorana ethanolic extract (OMEE) on cisplatin-induced nephrotoxicity. Eighteen male rats were divided into three groups as follows: a control group, a group treated with cisplatin (3 mg/kg body weight), and a group that received both cisplatin and OMEE (500 mg/kg body weight) for 14 days. Cisplatin induced a significant increase in creatinine, urea, uric acid, blood urea nitrogen, malondialdehyde, and nitric oxide levels. However, glutathione, superoxide dismutase, and catalase levels were significantly diminished. Conversely, OMEE significantly modulated the renal and oxidative markers negatively impacted by cisplatin. OMEE significantly reduced the effects of cisplatin-induced changes in renal and oxidative markers, possibly through its free radical scavenging activity. Thus, OMEE may be combined with cisplatin to alleviate nephrotoxicity in cancer chemotherapy. PMID:27164131
NASA Astrophysics Data System (ADS)
Sau, Jay; Barkeshli, Maissam
The idea of topological quantum computation (TQC) is to encode and manipulate quantum information in an intrinsically fault-tolerant manner by utilizing the physics of topologically ordered phases of matter. Currently, the most promising platforms for a topological qubit are either in terms of Majorana fermion zero modes (MZMs) in spin-orbit coupled superconducting nanowires or in terms of the Kitaev Z2 surface code. However, the topologically robust operations that are possible in these systems are not sufficient for realizing a universal gate set for topological quantum computation. Here, we show that an array of coupled semiconductor/superconductor nanowires with MZM edge states can be used to realize a more sophisticated type of non-Abelian defect, a genon in an Ising X Ising topological state. This leads to a possible implementation of the missing topologically protected pi/8 phase gate and thus paves a path for universal topological quantum computation based on semiconductor-superconductor nanowire technology. We provide detailed numerical estimates of the relevant energy scales, which we show to lie within accessible ranges. J. S. was supported by Microsoft Station Q, startup funds from the University of Maryland and NSF-JQI-PFC.
Soliman, Amel M; Desouky, Shreen; Marzouk, Mohamed; Sayed, Amany A
2016-05-05
Despite the fact that cisplatin is an important anticancer drug, its clinical utilization is limited by nephrotoxicity during long term medication. Combined cisplatin chemotherapy with plant extracts can diminish toxicity and enhance the antitumor efficacy of the drug. This study evaluated the effect of Originum majorana ethanolic extract (OMEE) on cisplatin-induced nephrotoxicity. Eighteen male rats were divided into three groups as follows: a control group, a group treated with cisplatin (3 mg/kg body weight), and a group that received both cisplatin and OMEE (500 mg/kg body weight) for 14 days. Cisplatin induced a significant increase in creatinine, urea, uric acid, blood urea nitrogen, malondialdehyde, and nitric oxide levels. However, glutathione, superoxide dismutase, and catalase levels were significantly diminished. Conversely, OMEE significantly modulated the renal and oxidative markers negatively impacted by cisplatin. OMEE significantly reduced the effects of cisplatin-induced changes in renal and oxidative markers, possibly through its free radical scavenging activity. Thus, OMEE may be combined with cisplatin to alleviate nephrotoxicity in cancer chemotherapy.
Majorana Fermion Induced Non-local Current Correlations in Spin-orbit Coupled Superconducting Wires
NASA Astrophysics Data System (ADS)
Liu, Jie; Zhang, Fu-Chun; Law, K. T.
2014-03-01
The observation of zero bias conductance peaks in semiconductor wire-superconductor heterostructures has generated great interest, and there is a hot debate on whether the observation is associated with Majorana Fermions (MFs) or other effects which enhance local Andreev reflections. In this work, we study the transport of a normal lead/semiconductor wire-superconductor heterostructure /normal lead junction. We show that when MF end states from the two ends of the wire are strongly coupled, the MF end states can suppress local Andreev reflections and strongly enhance crossed Andreev reflections (CARs), in which an electron from one lead is reflected as a hole in a different lead. In the CAR dominated regime, the current-current correlations between the two leads are strongly enhanced. Moreover, the Fano factor of a normal lead, which is the ratio of the shot noise to the average current, is reduced from 2e to e. Since the CAR associated effects are non-local effects and they cannot be induced by processes which enhance local Andreev reflections, therefore, the measurement of Fano factors and current-current correlations of the normal leads can be used to identify MFs.
Characterization of PPC Detectors for the MAJORANA DEMONSTRATOR Using a Scanning Collimated Source
NASA Astrophysics Data System (ADS)
Rager, Jamin; MAJORANA Collaboration
2017-01-01
The MAJORANA DEMONSTRATOR is a 76Ge double-beta decay experiment located at Sanford Underground Research Facility (SURF) that boasts cutting edge sensitivity and low backgrounds. I report on recent work measuring how charge drift-times vary with respect to the vertical and azimuthal position of physics events within a single-crystal HPGe detector used in the DEMONSTRATOR. Understanding these variations will allow for position reconstruction of physics events and identification of the detector's crystal axis, the latter of which will increase the detector's sensitivity to coherently-scattered Primakoff solar axions. Drift-time data was collected with an automated scanning station located at SURF, which used a 133Ba source to create a beam of collimated 81keV gamma-rays. Maximum likelihood analysis was used to fit the data to a set of models for comparison to ongoing work in pulse-shape simulations. This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics, the Particle Astrophysics and Nuclear Physics Programs of the National Science Foundation, and the Sanford Underground Research Facility.
A Waveform Library Technique for Multi-Site Identification with the MAJORANA DEMONSTRATOR
NASA Astrophysics Data System (ADS)
Buuck, Micah; MAJORANA Collaboration
2017-01-01
The MAJORANA DEMONSTRATOR is a low-background array of 44.8 kg of germanium detectors searching for neutrinoless double-beta (0 νββ) decay in germanium-76, deployed 4,850 feet underground at the Sanford Underground Research Facility in Lead, South Dakota, USA. We aim to demonstrate background levels low enough to justify construction of a ton-scale experiment which will be able to fully probe the inverted-hierarchy region of the 0 νββ decay phase-space. In addition to reducing background through materials selection and experimental design, we are developing a range of analysis-based background-suppression techniques. One example is a waveform-library-based technique to reject background multi-site interactions. Here we present an overview of the technique and its current status. This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics, the Particle Astrophysics and Nuclear Physics Programs of the National Science Foundation, and the Sanford Underground Research Facility.
Majorana Neutrino Masses by Spectroscopic Studies of Double Beta Decays and Moon
NASA Astrophysics Data System (ADS)
Ejiri, Hiroyasu
This is a brief review of spectroscopic studies of neutrino-less double beta decays (0νββ) and the MOON (Mo Observatory Of Neutrinos) project. It aims at studying the Majorana nature of neutrinos and the mass spectrum by spectroscopic studies of 0νββ with ν-mass sensitivity of
The DEMETER Science Mission Centre
NASA Astrophysics Data System (ADS)
Lagoutte, D.; Brochot, J. Y.; de Carvalho, D.; Elie, F.; Harivelo, F.; Hobara, Y.; Madrias, L.; Parrot, M.; Pinçon, J. L.; Berthelier, J. J.; Peschard, D.; Seran, E.; Gangloff, M.; Sauvaud, J. A.; Lebreton, J. P.; Stverak, S.; Travnicek, P.; Grygorczuk, J.; Slominski, J.; Wronowski, R.; Barbier, S.; Bernard, P.; Gaboriaud, A.; Wallut, J. M.
2006-04-01
The DEMETER Scientific Mission Centre (SMC) has been developed and is operated by the Laboratoire de Physique et Chimie de l'Environnement (LPCE). The SMC commands the instruments of the scientific payload, collects and distributes DEMETER data and associated products to the DEMETER international community. The SMC has been designed to maximize scientific return and to reduce development and exploitation costs for the DEMETER project. This paper describes the SMC's data processing system, data server and methods of payload operation, and presents associated hardware and software architectures.
Perceptual centres in speech - an acoustic analysis
NASA Astrophysics Data System (ADS)
Scott, Sophie Kerttu
Perceptual centres, or P-centres, represent the perceptual moments of occurrence of acoustic signals - the 'beat' of a sound. P-centres underlie the perception and production of rhythm in perceptually regular speech sequences. P-centres have been modelled both in speech and non speech (music) domains. The three aims of this thesis were toatest out current P-centre models to determine which best accounted for the experimental data bto identify a candidate parameter to map P-centres onto (a local approach) as opposed to the previous global models which rely upon the whole signal to determine the P-centre the final aim was to develop a model of P-centre location which could be applied to speech and non speech signals. The first aim was investigated by a series of experiments in which a) speech from different speakers was investigated to determine whether different models could account for variation between speakers b) whether rendering the amplitude time plot of a speech signal affects the P-centre of the signal c) whether increasing the amplitude at the offset of a speech signal alters P-centres in the production and perception of speech. The second aim was carried out by a) manipulating the rise time of different speech signals to determine whether the P-centre was affected, and whether the type of speech sound ramped affected the P-centre shift b) manipulating the rise time and decay time of a synthetic vowel to determine whether the onset alteration was had more affect on P-centre than the offset manipulation c) and whether the duration of a vowel affected the P-centre, if other attributes (amplitude, spectral contents) were held constant. The third aim - modelling P-centres - was based on these results. The Frequency dependent Amplitude Increase Model of P-centre location (FAIM) was developed using a modelling protocol, the APU GammaTone Filterbank and the speech from different speakers. The P-centres of the stimuli corpus were highly predicted by attributes of
NASA Astrophysics Data System (ADS)
Hutasoit, Jimmy A.; Balram, Ajit C.
2013-08-01
Potter and Lee have demonstrated the presence of Majorana zero modes at the ends of quasi-one-dimensional (1D) p+ip superconductors [Potter and Lee, Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.105.227003 105, 227003 (2010)]. Here, we use conformal field theory methods to show that interedge tunneling of the vortex excitations along the length of the channel is crucial for such localization. We then show that localization of Majorana modes occurs also in quasi-1D channels of the 5/2 fractional quantum Hall systems when modeled, following Moore and Read, as the p+ip paired state of composite fermions. Finally, we propose a tunnel-interferometry experiment to detect these modes, which should show a π phase shift of oscillations depending on whether or not a localized Majorana zero mode is present, which, in turn, can be controlled by varying the tunneling strength.
Quantum Transport through a Triple Quantum Dot System in the Presence of Majorana Bound States
NASA Astrophysics Data System (ADS)
Jiang, Zhao-Tan; Cao, Zhi-Yuan; Zhong, Cheng-Cheng
2016-05-01
We study the electron transport through a special quantum-dot (QD) structure composed of three QDs and two Majorana bound states (MBSs) using the nonequilibrium Green's function technique. This QD-MBS ring structure includes two channels with the two coupled MBSs being Channel 1 and one QD being Channel 2, and three types of transport processes such as the electron transmission (ET), the Andreev reflection (AR), and the crossed Andreev reflection (CAR). By comparing the ET, AR, and CAR processes through Channels 1 and 2, we make a systematic study on the transport properties of the QD-MBS ring. It is shown that there appear two kinds of characteristic transport patterns for Channels 1 and 2, as well as the interplay between the two patterns. Of particular interest is that there exists an AR-assisted ET process in Channel 2, which is different from that in Channel 1. Thus a clear “X” pattern due to the ET and AR processes appears in the ET, AR, and CAR transmission coefficients. Moreover, we study how Channel 2 affects the three transport processes when Channel 1 is tuned in the ET and CAR regimes. It is shown that the transport properties of the ET, AR and CAR processes can be adjusted by tuning the energy level of the QD embedded in Channel 2. We believe this research should be a helpful reference for understanding the transport properties in the QD-MBS coupled systems. Supported by National Natural Science Foundation of China under Grant No. 11274040, and by the Program for New Century Excellent Talents in University under Grant No. NCET-08-0044
NASA Astrophysics Data System (ADS)
Matsumoto, Shigeki; Mukhopadhyay, Satyanarayan; Tsai, Yue-Lin Sming
2016-09-01
We enumerate the set of simplified models which match onto the complete set of gauge invariant effective operators up to dimension six describing interactions of a singlet-like Majorana fermion dark matter with the standard model. Tree-level matching conditions for each case are worked out in the large mediator mass limit, defining a one-to-one correspondence between the effective operator coefficients and the simplified model parameters for weakly interacting models. Utilizing such a mapping, we compute the dark matter annihilation rate in the early universe, as well as other low-energy observables like nuclear recoil rates using the effective operators, while the simplified models are used to compute the dark matter production rates at high-energy colliders like LEP, LHC and future lepton colliders. Combining all relevant constraints with a profile-likelihood analysis, we then discuss the currently allowed parameter regions and prospects for future searches in terms of the effective operator parameters, reducing the model dependence to a minimal level. In the parameter region where such a model-independent analysis is applicable, and leaving aside the special dark matter mass regions where the annihilation proceeds through an s -channel Z or Higgs boson pole, the current constraints allow effective operator suppression scales (Λ ) of the order of a few hundred GeV for dark matter masses mχ>20 GeV at 95% C.L., while the maximum allowed scale is around 3 TeV for mχ˜O (1 TeV ) . An estimate of the future reach of ton-scale direct detection experiments and planned electron-positron colliders show that most of the remaining regions can be probed, apart from dark matter masses near half of the Z -boson mass (with 500 GeV <Λ <2 TeV ) and those beyond the kinematic reach of the future lepton colliders.
NASA Astrophysics Data System (ADS)
Klimenko, A. A.; Rumyantseva, N. S.
2017-01-01
We present effective Majorana neutrino mass limits < m ββ> obtained from the joint analysis of the recently published results of 76Ge and 136Xe neutrinoless double beta decay (0νββ) experiments, which was carried out by using the Bayesian calculations. Nuclear matrix elements (NMEs) used for the analysis are taken from the works, in which NMEs of 76Ge and 136Xe were simultaneously calculated. This reduced systematic errors connected with NME calculation techniques. The new effective Majorana neutrino mass limits < m ββ> less than [85.4-197.0] meV are much closer to the inverse neutrino mass hierarchy region.
Nuclear Science Centre, New Delhi
Mehta, G.; Potukuchi, P.; Roy, A.
1995-08-01
Argonne is collaborating with the Nuclear Science Centre (NSC), New Delhi, to develop a new type of superconducting accelerating structure for low-velocity heavy ions. A copper model has been evaluated and tests on the niobium prototype are currently in progress. Some technical details of this project are described in the Superconducting Linac Development section of this report. All funding for the prototype has come from the NSC, and they have also stationed two staff members at ATLAS for the past two years to gain experience and work on this project. Additional NSC personnel visited ATLAS for extended periods during 1994 for electronics and cryogenics experience and training. Two NSC staff members are scheduled to spend several months at ANL during 1995 to continue tests and developments of the prototype resonators and to initiate fabrication of the production models for their linac project.
The International Centre for Theoretical Physics
NASA Astrophysics Data System (ADS)
Hussain, Faheem
2008-07-01
This talk traces in brief the genesis of the Abdus Salam International Centre for Theoretical Physics, Trieste, as one of Prof. Abdus Salam's major achievements. It outlines why Salam felt the necessity for establishing such a centre to help physicists in the developing world. It situates the founding of the Centre within Salam's broader vision of the causes of underdevelopment and of science as an engine for scientific, technological, economic and social development. The talk reviews the successes and failures of the ICTP and gives a brief overall view of the current status of the Centre.
NASA Astrophysics Data System (ADS)
Cirilo-Lombardo, Diego Julio
2015-06-01
The two-dimensional charge transport with parallel (in plane) magnetic field is considered from the physical and mathematical point of view. To this end, we start with the magnetic field parallel to the plane of charge transport, in sharp contrast to the configuration described by the theorems of Aharonov and Casher where the magnetic field is perpendicular. We explicitly show that the specific form of the arising equation enforces the respective field solution to fulfill the Majorana condition. Consequently, as soon any physical system is represented by this equation, the rise of fields with Majorana type behavior is immediately explained and predicted. In addition, there exists a quantized particular phase that removes the action of the vector potential producing interesting effects. Such new effects are able to explain due to the geometrical framework introduced, several phenomenological results recently obtained in the area of spintronics and quantum electronic devices. The quantum ring as spin filter is worked out in this framework and also the case of the quantum Hall effect.
García-Risco, Mónica R; Mouhid, Lamia; Salas-Pérez, Lilia; López-Padilla, Alexis; Santoyo, Susana; Jaime, Laura; Ramírez de Molina, Ana; Reglero, Guillermo; Fornari, Tiziana
2017-03-01
Asteraceae (Achillea millefolium and Calendula officinalis) and Lamiaceae (Melissa officinalis and Origanum majorana) extracts were obtained by applying two sequential extraction processes: supercritical fluid extraction with carbon dioxide, followed by ultrasonic assisted extraction using green solvents (ethanol and ethanol:water 50:50). The extracts were analyzed in terms of the total content of phenolic compounds and the content of flavonoids; the volatile oil composition of supercritical extracts was analyzed by gas chromatography and the antioxidant capacity and cell toxicity was determined. Lamiaceae plant extracts presented higher content of phenolics (and flavonoids) than Asteraceae extracts. Regardless of the species studied, the supercritical extracts presented the lowest antioxidant activity and the ethanol:water extracts offered the largest, following the order Origanum majorana > Melissa officinalis ≈ Achillea millefolium > Calendula officinalis. However, concerning the effect on cell toxicity, Asteraceae (especially Achillea millefolium) supercritical extracts were significantly more efficient despite being the less active as an antioxidant agent. These results indicate that the effect on cell viability is not related to the antioxidant activity of the extracts.
NASA Astrophysics Data System (ADS)
Chen, HuaJun; Zhu, KaDi
2015-05-01
Majorana fermions (MFs) are exotic particles that are their own anti-particles. Currently, the search for MFs occurring as quasiparticle excitations in condensed matter systems has attracted widespread interest, because of their importance in fundamental physics and potential applications in topological quantum computation based on solid-state devices. Motivated by recent experimental progress towards the detection and manipulation of MFs in hybrid semiconductor/superconductor heterostructures, in this review, we present a novel proposal to probe MFs in all-optical domain. We introduce a single quantum dot (QD), a hybrid quantum dot-nanomechanical resonators (QD-NR) system, and a carbon nanotube (CNT) resonator implanted in a single electron spin system with optical pump-probe technology to detect MFs, respectively. With this scheme, a possible Majorana signature is investigated via the probe absorption spectrum and nonlinear optical Kerr effect, and the coupling strength between MFs and the QD or the single electron spin is also determined. In the hybrid QD-NR system, vibration of the NR will enhance the nonlinear optical effect, which makes the MFs more sensitive for detection. In the CNT resonator with a single electron, the single electron spin can be considered as a sensitive probe, and the CNT resonator behaved as a phonon cavity is robust for detecting of MFs. This optical scheme will provide another method for the detection MFs and will open the door for new applications ranging from robust manipulation of MFs to quantum information processing based on MFs.
NASA Astrophysics Data System (ADS)
Vernek, Edson; Penteado, Poliana; Seridonio, Antonio; Egues, José C.
2014-03-01
The search for Majorana bound state (MBS) is topological superconductor nanowires is currently a topic of great interest. Despite the various theoretical proposals and the experimental results, the question of whether the possible signatures of MBS can be distinguished from those arising from other phenomena such as the Kondo effect is still under debate. A recent proposal for detecting MBS using a quantum dot coupled to normal two leads and to a topological quantum wire has proven to be very appropriate structure to investigate this problem. In this system, the presence of MBS in the wire is marked as a e2 / 2 h conductance through the dot. In this work we find, that the e2 / 2 h conductance peak is not per se an distinct signature of a MBS in the wire. We show instead that it results from a leaking of the Majorana state into the dot. Moreover, by gating the dot level (ɛd) far away below and above the Fermi level of the leads (ɛF), the conductance remains at e2 / 2 h . The surviving of the conductance plateau for ɛd >ɛF contrasts with Kondo effect plateau known to emerge only for ɛd <ɛF . This work is supported by FAPESP, CNPq, CAPES and FAPEMIG.
NASA Astrophysics Data System (ADS)
Huo, Dong-Ming
2016-07-01
Using the Green's function technique, we respectively investigate the electron transport properties of two spin components through the system of a T-shaped double quantum dot structure coupled to a Majorana bound state, in which only one quantum dot is connected with two metallic leads. We explore the interplay between the Fano effect and the MBSs for different dot-MBS coupling strength λ, dot-dot coupling strength t, and MBS-MBS coupling strength ɛM in the noninteracting case. Then the Coulomb interaction and magnetic field effect on the conductance spectra are investigated. Our results indicate that G↓(ω) is not affected by the Majorana bound states, but a "0.5" conductance signature occurs in the vicinities of Fermi level of G↑(ω). This robust property persists for a wide range of dot-dot coupling strength and dot-MBS coupling strength, but it can be destroyed by Coulomb interaction in quantum dots. By adjusting the size and direction of magnetic field around the quantum dots, the "0.5" conductance signature damaged by U can be restored. At last, the spin magnetic moments of two dots by applying external magnetic field are also predicted.
NASA Astrophysics Data System (ADS)
Gehman, Victor
2010-02-01
The Majo-ra-na collaboration will search for neutrinoless double-beta decay (0νββ) by fielding an array of high-purity germanium (HPGe) detectors in ultra-clean electroformed-copper cryostats deep underground. Recent advances in HPGe detector technology, in particular P-type Point-Contact (PPC) detectors, present exciting new techniques for identifying and reducing backgrounds to the 0νββ signal. This should result in greatly improved sensitivity over previous generation experiments. The very low energy threshold attainable with PPC detectors also provides for a broader physics program including searches for dark matter and axions. The Majo-ra-na De-mon-strat-or is an R&D program that will field three ˜20 kg modules of PPC detectors at Sanford Underground Laboratory. Half of the detectors will be enriched to 86% in ^76Ge. Here, we will cover the motivation, design, recent progress and current status of this effort, with special attention to its physics reach. )
NASA Astrophysics Data System (ADS)
Ejiri, H.; Doe, P.; Elliott, S. R.; Engel, J.; Finger, M., Jr.; Finger, M.; Fushimi, K.; Gehman, V.; Greenfield, M.; Hazama, R.; Kavitov, P.; Kekelidze, V.; Nakamura, H.; Nomachi, M.; Robertson, R. G. H.; Shima, T.; Slunecka, M.; Shirkov, G.; Sissakian, A.; Titov, A.; Umehara, S.; Vaturin, V.; Voronov, V.; Wilkerson, J. F.; Will, D. I.; Yoshida, S.; Vrba, V.
2008-08-01
The MOON (Majorana/Mo Observatory Of Neutrinos) project aims at studies of the Majorana nature of the neutrino ( ν) and the ν-mass spectrum by spectroscopic experiments of neutrino-less double beta decays (0 νββ) with the ν-mass sensitivity of < m {/ν m }> = 100-30 meV. The solid scintillator option of the MOON detector is a super ensemble of multi-layer modules, each being composed by PL scintillator plates and position-sensitive detector planes with good overall energy resolution of σ ≈ 2% at the Q ββ ≈ 3 MeV. Thin ββ source films are interleaved between the detector planes. High localization of the two β tracks enables one to select true signals and reject BG ones. The multi-layer structure of the detector makes it realistic to build a compact ton-scale detector. MOON with detector ≠ ββ source is used for studying 0 νββ decays from 100Mo, 82Se and other ββ isotopes with large Q ββ . Real-time exclusive measurements of low energy solar neutrinos can be made by observing inverse β rays from solar- ν captures of 100Mo in delayed coincidence with the subsequent β decay of 100Tc.
The Press Research Centre, 1956-1976.
ERIC Educational Resources Information Center
Press Research Centre, Krakow (Poland).
In 1956, the Press Research Centre was established in Cracow, Poland by a group of journalists and publishers, for the purpose of instituting press research that would have practical applications. The aims of the Centre were to conduct studies on the history of the Polish press, the contemporary press, press readership, and editorial techniques.…
The Irish Centre for Talented Youth
ERIC Educational Resources Information Center
Gilheany, Sheila
2005-01-01
Conducting potency tests on penicillin, discussing rocket technology with a NASA astronaut, analysing animal bone fragments from medieval times, these are just some of the activities which occupy the time of students at The Irish Centre for Talented Youth. The Centre identifies young students with exceptional academic ability and then provides…
The European standards of Haemophilia Centres
Giangrande, Paul; Calizzani, Gabriele; Menichini, Ivana; Candura, Fabio; Mannucci, Pier Mannuccio; Makris, Michael
2014-01-01
Introduction The European haemophilia community of professionals and patients has agreed on the principles of haemophilia care to address comprehensive optimal delivery of care which is nowadays scattered throughout Europe. Many of the health facilities call themselves Haemophilia Centres despite their variation in size, expertise and services provided. Only a small number of countries have Haemophilia Centre accreditation systems in place. Methods In the framework of the European Haemophilia Network project, following an inclusive process of stakeholder involvement, the European Guidelines for the certification of haemophilia centres have been developed in order to set quality standards for European Haemophilia Centres and criteria for their certification. Results The Guidelines define the standards and criteria for the designation of two levels of care delivery: European Haemophilia Treatment Centres, providing local routine care, and European Haemophilia Comprehensive Care Centres, providing specialised and multi-disciplinary care and functioning as tertiary referral centres. Additionally, they define standards about general requirements, patient care, provision of an advisory service and establishment of network of clinical and specialised services. Conclusions The implementation of the European Guidelines for the certification of Haemophilia Centres will contribute to the reduction of health inequalities through the standardisation of quality of care in European Union Member States and could represent a model to be taken into consideration for other rare disease groups. PMID:24922293
Promotion in Call Centres: Opportunities and Determinants
ERIC Educational Resources Information Center
Gorjup, Maria Tatiana; Valverde, Mireia; Ryan, Gerard
2008-01-01
Purpose: The purpose of this paper is to examine the quality of jobs in call centres by focusing on the opportunities for promotion in this sector. More specifically, the research questions focus on discovering whether promotion is common practise in the call centre sector and on identifying the factors that affect this.…
The Canadian Astronomy Data Centre
NASA Astrophysics Data System (ADS)
Ball, Nicholas M.; Schade, D.; Astronomy Data Centre, Canadian
2011-01-01
The Canadian Astronomy Data Centre (CADC) is the world's largest astronomical data center, holding over 0.5 Petabytes of information, and serving nearly 3000 astronomers worldwide. Its current data collections include BLAST, CFHT, CGPS, FUSE, Gemini, HST, JCMT, MACHO, MOST, and numerous other archives and services. It provides extensive data archiving, curation, and processing expertise, via projects such as MegaPipe, and enables substantial day-to-day collaboration between resident astronomers and computer specialists. It is a stable, powerful, persistent, and properly supported environment for the storage and processing of large volumes of data, a condition that is now absolutely vital for their science potential to be exploited by the community. Through initiatives such as the Common Archive Observation Model (CAOM), the Canadian Virtual Observatory (CVO), and the Canadian Advanced Network for Astronomical Research (CANFAR), the CADC is at the global forefront of advancing astronomical research through improved data services. The CAOM aims to provide homogeneous data access, and hence viable interoperability between a potentially unlimited number of different data collections, at many wavelengths. It is active in the definition of numerous emerging standards within the International Virtual Observatory, and several datasets are already available. The CANFAR project is an initiative to make cloud computing for storage and data-intensive processing available to the community. It does this via a Virtual Machine environment that is equivalent to managing a local desktop. Several groups are already processing science data. CADC is also at the forefront of advanced astronomical data analysis, driven by the science requirements of astronomers both locally and further afield. The emergence of 'Astroinformatics' promises to provide not only utility items like object classifications, but to directly enable new science by accessing previously undiscovered or intractable
NASA Astrophysics Data System (ADS)
Schade, D.
2016-06-01
Well-designed astronomical surveys are powerful and have consistently been keystones of scientific progress. The Byurakan Surveys using a Schmidt telescope with an objective prism produced a list of about 3000 UV-excess Markarian galaxies but these objects have stimulated an enormous amount of further study and appear in over 16,000 publications. The CFHT Legacy Surveys used a wide-field imager to cover thousands of square degrees and those surveys are mentioned in over 1100 publications since 2002. Both ground and space-based astronomy have been increasing their investments in survey work. Survey instrumentation strives toward fair samples and large sky coverage and therefore strives to produce massive datasets. Thus we are faced with the "big data" problem in astronomy. Survey datasets require specialized approaches to data management. Big data places additional challenging requirements for data management. If the term "big data" is defined as data collections that are too large to move then there are profound implications for the infrastructure that supports big data science. The current model of data centres is obsolete. In the era of big data the central problem is how to create architectures that effectively manage the relationship between data collections, networks, processing capabilities, and software, given the science requirements of the projects that need to be executed. A stand alone data silo cannot support big data science. I'll describe the current efforts of the Canadian community to deal with this situation and our successes and failures. I'll talk about how we are planning in the next decade to try to create a workable and adaptable solution to support big data science.
Review of CERN Data Centre Infrastructure
NASA Astrophysics Data System (ADS)
Andrade, P.; Bell, T.; van Eldik, J.; McCance, G.; Panzer-Steindel, B.; Coelho dos Santos, M.; Traylen and, S.; Schwickerath, U.
2012-12-01
The CERN Data Centre is reviewing strategies for optimizing the use of the existing infrastructure and expanding to a new data centre by studying how other large sites are being operated. Over the past six months, CERN has been investigating modern and widely-used tools and procedures used for virtualisation, clouds and fabric management in order to reduce operational effort, increase agility and support unattended remote data centres. This paper gives the details on the project's motivations, current status and areas for future investigation.
Planetary Radars Operating Centre PROC
NASA Astrophysics Data System (ADS)
Catallo, C.; Flamini, E.; Seu, R.; Alberti, G.
2007-12-01
Planetary exploration by means of radar systems, mainly using Ground Penetrating Radars (GPR) plays an important role in Italy. Numerous scientific international space programs are currently carried out jointly with ESA and NASA by Italian Space Agency, the scientific community and the industry. Three important experiments under Italian leadership ( designed and manufactured by the Italian industry), provided by ASI either as contribution to ESA programs either within a NASA/ASI joint venture framework, are now operating: MARSIS on-board Mars Express, SHARAD on-board Mars Reconnaissance Orbiter and CASSINI Radar on-board Cassini spacecraft. In order to support all the scientific communities, institutional customers and experiment teams operation three Italian dedicated operational centers have been realized, namely SHOC, (Sharad Operating Centre), MOC (Marsis Operating Center) and CASSINI PAD ( Processing Altimetry Data). Each center is dedicated to a single instrument management and control, data processing and distribution. Although they had been conceived to operate autonomously and independently one from each other, synergies and overlaps have been envisaged leading to the suggestion of a unified center, the Planetary Radar Processing Center (PROC). PROC is conceived in order to include the three operational centers, namely SHOC, MOC and CASSINI PAD, either from logistics point of view and from HW/SW capabilities point of view. The Planetary Radar Processing Center shall be conceived as the Italian support facility to the scientific community for on-going and future Italian planetary exploration programs. Therefore, scalability, easy use and management shall be the design drivers. The paper describes how PROC is designed and developed, to allow SHOC, MOC and CASSINI PAD to operate as before, and to offer improved functionalities to increase capabilities, mainly in terms of data exchange, comparison, interpretation and exploitation. Furthermore, in the frame of
NASA Astrophysics Data System (ADS)
Bannon, Liam J.
The field of HCI has evolved and expanded dramatically since its origin in the early 1980’s. The HCI community embraces a large community of researchers and practitioners around the world, from a variety of disciplinary backgrounds in the human and social sciences, engineering and informatics, and more recently, the arts and design disciplines. This kaleidoscope of cultures and disciplines as seen at INTERACT Conferences provides a rich pool of resources for examining our field. Applications are increasingly exploring our full range of sensory modalities, and merging the digital and physical worlds. WiFi has opened up a huge design space for mobile applications. A focus on usability of products and services has been complemented by an emphasis on engagement, enjoyment and experience. With the advent of ubiquitous computing, and the emergence of “The Internet of Things”, new kinds of more open infrastructures make possible radically new kinds of applications. The sources of innovation have also broadened, to include human and social actors outside of the computing and design organizations. The question is to what extent is our mainstream thinking in the HCI field ready for the challenges of this Brave New World? Do the technological and social innovations that we see emerging require us to re-shape, or even, re-create, our field, or is it a case of a more gradual evolution and development of that which we already know? In this closing Keynote, I will provide a perspective on the evolution and development of the HCI field, looking backwards as well as forwards, in order to determine what are some of the changes of significance in the field. This “broad-brush” approach to what I term “ human-centred design” will be complemented by the examination of specific projects and applications, to help anchor some of the discussion. Areas such as user-centred design, participatory design, computer-supported cooperative work and learning, and interaction design, in
Snake states and Majorana's in graphene quantum dots in the presence of a p-n junction
NASA Astrophysics Data System (ADS)
Peeters, Francois; Zarenia, M.; Pereira, J. M., Jr.; Farias, G. A.
2013-03-01
We investigate the magnetic interface states of graphene quantum dots that contain p-n junctions. Within a tight-binding approach, we consider rectangular quantum dots in the presence of a perpendicular magnetic field containing p-n, as well as p-n-p and n-p-n junctions. The results show the interplay between the edge states associated with the zigzag terminations of the sample and the snake states that arise at the p-n junction, due to the overlap between electron and hole states at the potential interface. Remarkable localized states are found at the crossing of the p-n junction with the zigzag edge having a dumb-bell shaped electron distribution. These states are localized Majorana states. The results are presented as function of the junction parameters and the applied magnetic flux.
Fano effect in the Andreev reflection of the Aharonov-Bohm-Fano ring with Majorana bound states
NASA Astrophysics Data System (ADS)
Jiang, Cui; Zheng, Yi-Song
2015-06-01
The Andreev reflection in an Aharonov-Bohm-Fano ring induced by Majorana bound states (MBSs) is theoretically investigated. We find that compared with the Fano effect in the normal electron tunneling process, the Fano effect here is more determined by the structural parameters, i.e., the quantum dot level, the dot-MBS coupling, and the dot-MBS and MBS-lead couplings. By transforming the ring into its Nambu representation, we present a comprehensive analysis about the quantum interference in the Andreev reflection, and then explain the reason for the occurrence of the Fano effect. These results will be helpful for understanding the quantum interference in the MBS-assisted Andreev reflection.
NASA Astrophysics Data System (ADS)
Gilliss, Thomas; MAJORANA DEMONSTRATOR Collaboration
2017-01-01
The MAJORANA DEMONSTRATOR advances toward measurements of the neutrinoless double-beta decay of 76Ge. Detectors employed in the DEMONSTRATOR are subject to cosmogenic spallation during production and processing, resulting in activation of certain long-lived radioisotopes. Activation of these cosmogenic isotopes is mitigated by shielded storage of detectors and through underground operation of the DEMONSTRATOR at the 4850 ft level of the Sanford Underground Research Facility. In this work, we explore the appearance and reduction of cosmogenic contributions to the DEMONSTRATOR background spectrum. This work is supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics, the Particle Astrophysics and Nuclear Physics Programs of the National Science Foundation, and the Sanford Underground Research Facility.
Potter, Andrew C; Lee, Patrick A
2014-03-21
In mean-field descriptions of nodal d-wave superconductors, generic edges exhibit dispersionless Majorana fermion bands at zero energy. These states give rise to an extensive ground-state degeneracy, and are protected by time-reversal symmetry. We argue that the infinite density of states of these flat bands make them inherently unstable to interactions, and show that repulsive interactions lead to edge ferromagnetism which splits the flat bands. This edge ferromagnetism offers an explanation for the observation of the splitting of zero-bias peaks in edge tunneling in high-Tc cuprate superconductors. We argue that this mechanism for splitting is more likely than previously proposed scenarios and describe its experimental consequences.
Ueno, Yuji; Yamakage, Ai; Tanaka, Yukio; Sato, Masatoshi
2013-08-23
Crystal point group symmetry is shown to protect Majorana fermions (MFs) in spinfull superconductors (SCs). We elucidate the condition necessary to obtain MFs protected by the point group symmetry. We argue that superconductivity in Sr2RuO4 hosts a topological phase transition to a topological crystalline SC, which accompanies a d-vector rotation under a magnetic field along the c axis. Taking all three bands and spin-orbit interactions into account, symmetry-protected MFs in the topological crystalline SC are identified. Detection of such MFs provides evidence of the d-vector rotation in Sr2RuO4 expected from Knight shift measurements but not yet verified.
Yoshitake, Junki; Nasu, Joji; Motome, Yukitoshi
2016-10-07
Experimental identification of quantum spin liquids remains a challenge, as the pristine nature is to be seen in asymptotically low temperatures. We here theoretically show that the precursor of quantum spin liquids appears in the spin dynamics in the paramagnetic state over a wide temperature range. Using the cluster dynamical mean-field theory and the continuous-time quantum Monte Carlo method, which are newly developed in the Majorana fermion representation, we calculate the dynamical spin structure factor, relaxation rate in nuclear magnetic resonance, and magnetic susceptibility for the honeycomb Kitaev model whose ground state is a canonical example of the quantum spin liquid. We find that dynamical spin correlations show peculiar temperature and frequency dependence even below the temperature where static correlations saturate. The results provide the experimentally accessible symptoms of the fluctuating fractionalized spins evincing the quantum spin liquids.
Landau-Zener-Stückelberg-Majorana interference in a 3D transmon driven by a chirped microwave
NASA Astrophysics Data System (ADS)
Gong, Ming; Zhou, Yu; Lan, Dong; Fan, Yunyi; Pan, Jiazheng; Yu, Haifeng; Chen, Jian; Sun, Guozhu; Yu, Yang; Han, Siyuan; Wu, Peiheng
2016-03-01
By driving a 3D transmon with microwave fields, we generate an effective avoided energy-level crossing. Then we chirp microwave frequency, which is equivalent to driving the system through the avoided energy-level crossing by sweeping the avoided crossing. A double-passage chirp produces Landau-Zener-Stückelberg-Majorana (LZSM) interference that agree well with the numerical results, especially with the initial state being an eigen-energy state in the center of an avoided level crossing. A time-resolved state tomography measurement is performed in the evolution of LZSM interference, showing an experimental evidence for the dynamical evolution of quantum state. Our method is fully applicable to other quantum systems that contain no intrinsic avoided level crossing, providing an alternative approach for quantum control and quantum simulation.
NASA Astrophysics Data System (ADS)
Rodionov, Ya. I.; Kugel, K. I.; Nori, Franco
2016-11-01
Using the Landau-Zener-Stückelberg-Majorana-type (LZSM) semiclassical approach, we study both graphene and a thin film of a Weyl semimetal subjected to a strong ac electromagnetic field. The spectrum of quasienergies in the Weyl semimetal turns out to be similar to that of a graphene sheet. It has been predicted qualitatively that the transport properties of strongly irradiated graphene oscillate as a function of the radiation intensity [S. V. Syzranov et al., Phys. Rev. B 88, 241112 (2013)], 10.1103/PhysRevB.88.241112. Here we obtain rigorous quantitative results for a driven linear conductance of graphene and a thin film of a Weyl semimetal. The exact quantitative structure of oscillations exhibits two contributions. The first one is a manifestation of the Ramsauer-Townsend effect, while the second contribution is a consequence of the LZSM interference defining the spectrum of quasienergies.
NASA Astrophysics Data System (ADS)
Yoshitake, Junki; Nasu, Joji; Motome, Yukitoshi
2016-10-01
Experimental identification of quantum spin liquids remains a challenge, as the pristine nature is to be seen in asymptotically low temperatures. We here theoretically show that the precursor of quantum spin liquids appears in the spin dynamics in the paramagnetic state over a wide temperature range. Using the cluster dynamical mean-field theory and the continuous-time quantum Monte Carlo method, which are newly developed in the Majorana fermion representation, we calculate the dynamical spin structure factor, relaxation rate in nuclear magnetic resonance, and magnetic susceptibility for the honeycomb Kitaev model whose ground state is a canonical example of the quantum spin liquid. We find that dynamical spin correlations show peculiar temperature and frequency dependence even below the temperature where static correlations saturate. The results provide the experimentally accessible symptoms of the fluctuating fractionalized spins evincing the quantum spin liquids.
Fano effect in an AB interferometer with a quantum dot side-coupled to a single Majorana bound state
NASA Astrophysics Data System (ADS)
Zeng, Qi-Bo; Chen, Shu; Lü, Rong
2016-02-01
We study the conductance and interference effects through an AB interferometer with an embedded quantum dot (QD) side-coupled to a single Majorana bound state (MBS) by using non-equilibrium Green's function method. The energy levels appearing in the QD are calculated by diagonalizing the Hamiltonian of the embedded QD-MBS system. When the single QD energy level ɛ0 is set to 0, there are three discrete energy levels in the QD appearing at around ω = 0, ±√{ɛM2 + 2λ2 } due to the coupling with MBS where ɛM is the coupling strength between the two MBSs at the two ends of the nanowire and λ is the coupling strength between the MBS and the QD. Asymmetric Fano lineshapes are found around these levels in the conductance due to the interference between electrons traversing through different paths. The phase shift of electrons through the QD changes from π / 2 to - π / 2 at each of these three energy values. However, the phase does not vary smoothly between these three energy levels but shows severe changes from - π / 2 to π / 2 at ω = ±√{ɛM2 +λ2 }. As a comparison, we also study the similar AB interferometer in which the QD-MBS system is replaced by a normal QD-QD system or a simple single QD system, which shows only two or one Fano peak and the phase shifts from π / 2 to - π / 2 only at the Fano peaks. These differences reflect the distinct influences of Majorana bound state on the transport properties of AB interferometer.
Identity Theft: A Study in Contact Centres
NASA Astrophysics Data System (ADS)
Moir, Iain; Weir, George R. S.
This paper explores the recent phenomenon of identity theft. In particular, it examines the contact centre environment as a mechanism for this to occur. Through a survey that was conducted amongst forty-five contact centre workers in the Glasgow area we determined that contact centres can and do provide a mechanism for identity theft. Specifically, we found a particularly high incidence of agents who had previously dealt with phone calls that they considered suspicious. Furthermore, there are agents within such environments who have previously been offered money in exchange for customers' details, or who know of fellow workers who received such offers. Lastly, we identify specific practices within contact centres that may contribute to the likelihood of identity theft.
Perspectives on recycling centres and future developments.
Engkvist, I-L; Eklund, J; Krook, J; Björkman, M; Sundin, E
2016-11-01
The overall aim of this paper is to draw combined, all-embracing conclusions based on a long-term multidisciplinary research programme on recycling centres in Sweden, focussing on working conditions, environment and system performance. A second aim is to give recommendations for their development of new and existing recycling centres and to discuss implications for the future design and organisation. Several opportunities for improvement of recycling centres were identified, such as design, layout, ease with which users could sort their waste, the work environment, conflicting needs and goals within the industry, and industrialisation. Combining all results from the research, which consisted of different disciplinary aspects, made it possible to analyse and elucidate their interrelations. Waste sorting quality was recognized as the most prominent improvement field in the recycling centre system. The research identified the importance of involving stakeholders with different perspectives when planning a recycling centre in order to get functionality and high performance. Practical proposals of how to plan and build recycling centres are given in a detailed checklist.
The Imperial College Thermophysical Properties Data Centre
NASA Astrophysics Data System (ADS)
Angus, S.; Cole, W. A.; Craven, R.; de Reuck, K. M.; Trengove, R. D.; Wakeham, W. A.
1986-07-01
The IUPAC Thermodynamic Tables Project Centre in London has at its disposal considerable expertise on the production and utilization of high-accuracy equations of state which represent the thermodynamic properties of substances. For some years they have been content to propagate this information by the traditional method of book production, but the increasing use of the computer in industry for process design has shown that an additional method was needed. The setting up of the IUPAC Transport Properties Project Centre, also at Imperial College, whose products would also be in demand by industry, afforded the occasion for a new look at the problem. The solution has been to set up the Imperial College Thermophysical Properties Data Centre, which embraces the two IUPAC Project Centres, and for it to establish a link with the existing Physical Properties Data Service of the Institution of Chemical Engineers, thus providing for the dissemination of the available information without involving the Centres in problems such as those of marketing and advertising. This paper outlines the activities of the Centres and discusses the problems in bringing their products to the attention of industry in suitable form.
NASA Astrophysics Data System (ADS)
Gnezdilov, N. V.; Diez, M.; Pacholski, M. J.; Beenakker, C. W. J.
2016-09-01
We compare the thermal conductance Gthermal (at temperature T ) and the electrical shot-noise power Pshot (at bias voltage V ≫kBT /e ) of Majorana fermions on the two-dimensional surface of a three-dimensional topological superconductor. We present analytical and numerical calculations to demonstrate that, for a local coupling between the superconductor and metal contacts, Gthermal/Pshot=L T /e V (with L the Lorenz number). This relation is ensured by the combination of electron-hole and time-reversal symmetries, irrespective of the microscopics of the surface Hamiltonian, and provides for a purely electrical way to detect the charge-neutral Majorana surface states. A surface of aspect ratio W /L ≫1 has the universal shot-noise power Pshot=(W /L ) ×(e2/h ) ×(e V /2 π ) .
NASA Astrophysics Data System (ADS)
Asano, Yasuhiro; Tanaka, Yukio
2013-03-01
We discuss a strong relationship between Majorana fermions and odd-frequency Cooper pairs which appear at a disordered normal (N) nanowire attached to a topologically nontrivial superconducting (S) one. The transport properties in superconducting nanowire junctions show universal behaviors irrespective of the degree of disorder: the quantized zero-bias differential conductance at 2e2/h in NS junction and the fractional current-phase (J-φ) relationship of the Josephson effect in SNS junction J∝sin(φ/2). Such behaviors are exactly the same as those found in the anomalous proximity effect of odd-parity spin-triplet superconductors. We show that the odd-frequency pairs exist wherever the Majorana fermions stay.
CMS centres worldwide: A new collaborative infrastructure
Taylor, Lucas; Gottschalk, Erik; /Fermilab
2010-01-01
The CMS Experiment at the LHC is establishing a global network of inter-connected 'CMS Centres' for controls, operations and monitoring. These support: (1) CMS data quality monitoring, detector calibrations, and analysis; and (2) computing operations for the processing, storage and distribution of CMS data. We describe the infrastructure, computing, software, and communications systems required to create an effective and affordable CMS Centre. We present our highly successful operations experiences with the major CMS Centres at CERN, Fermilab, and DESY during the LHC first beam data-taking and cosmic ray commissioning work. The status of the various centres already operating or under construction in Asia, Europe, Russia, South America, and the USA is also described. We emphasise the collaborative communications aspects. For example, virtual co-location of experts in CMS Centres Worldwide is achieved using high-quality permanently-running 'telepresence' video links. Generic Web-based tools have been developed and deployed for monitoring, control, display management and outreach.
Guerra-Boone, Laura; Alvarez-Román, Rocío; Alvarez-Román, Rocío; Salazar-Aranda, Ricardo; Torres-Cirio, Anabel; Rivas-Galindo, Verónica Mayela; de-Torres, Noemí Waksman; González, Gloria; Pérez-López, Luis Alejandro
2015-01-01
There have been no reports of antifungal activity and composition of extracts from Thymus vulgaris, Rosmarinus officinalis or Origanum majorana from northeastern México. Antifungal activity of these oils against Trichophyton rubrum, Trichophyton tonsurans, Trichophyton mentagrophytes, Microsporum gypseum, Microsporum canis and Epidermophyton floccosum was measured by diffusion assay. Additionally, antibacterial and antioxidant activities were evaluated. Antibacterial activity against Staphylococcus aureus and Streptococcus pyogenes was examined by microdilution. Antioxidant activity was assessed by 2,2-difenil-1-picrilhidracil reduction test. The plant oils were characterized by both GC/MS and GC/FID. Oils of T. vulgaris and O. majorana showed growth inhibition activity against dermatophytes, especially T. vulgaris oil, which completely inhibited growth of all tested dermatophytes. The oils also showed bioactivity against bacteria, with minimum inhibitory concentration (MIC) values between 62.5 and 500 μg/mL. The antioxidant activity of the oils was low, with effective concentration (EC50) values <250μg/mL. The major components in the oils were as follows: T. vulgaris, o-cymene, μ-terpinene, thymol and carvacrol; R. officinalis, terpinen-4-ol and 1,8-cineole; O. majorana, terpinen-4-ol and thymol.
Optimizing Data Centre Energy and Environmental Costs
NASA Astrophysics Data System (ADS)
Aikema, David Hendrik
Data centres use an estimated 2% of US electrical power which accounts for much of their total cost of ownership. This consumption continues to grow, further straining power grids attempting to integrate more renewable energy. This dissertation focuses on assessing and reducing data centre environmental and financial costs. Emissions of projects undertaken to lower the data centre environmental footprints can be assessed and the emission reduction projects compared using an ISO-14064-2-compliant greenhouse gas reduction protocol outlined herein. I was closely involved with the development of the protocol. Full lifecycle analysis and verifying that projects exceed business-as-usual expectations are addressed, and a test project is described. Consuming power when it is low cost or when renewable energy is available can be used to reduce the financial and environmental costs of computing. Adaptation based on the power price showed 10--50% potential savings in typical cases, and local renewable energy use could be increased by 10--80%. Allowing a fraction of high-priority tasks to proceed unimpeded still allows significant savings. Power grid operators use mechanisms called ancillary services to address variation and system failures, paying organizations to alter power consumption on request. By bidding to offer these services, data centres may be able to lower their energy costs while reducing their environmental impact. If providing contingency reserves which require only infrequent action, savings of up to 12% were seen in simulations. Greater power cost savings are possible for those ceding more control to the power grid operator. Coordinating multiple data centres adds overhead, and altering at which data centre requests are processed based on changes in the financial or environmental costs of power is likely to increase this overhead. Tests of virtual machine migrations showed that in some cases there was no visible increase in power use while in others power use
Bureaucracy, professionalization and school centred innovation strategies
NASA Astrophysics Data System (ADS)
Morris, Paul
1990-03-01
This paper examines an attempt to promote a school centred innovation strategy within a highly centralized educational system. The School Based Curriculum Project Scheme, which was introduced into Hong Kong in 1988, is analysed in terms of a professional-bureaucratic dichotomy. It is argued that the operational details of the scheme are designed to satisfy a range of bureaucratic concerns and these are not conducive to promoting the professional work ethic which is required for school centred innovation. Finally the paper identifies the implications which arise for policies designed to promote curriculum innovation.
Byurakan Astrophysical Observatory as Cultural Centre
NASA Astrophysics Data System (ADS)
Mickaelian, A. M.; Farmanyan, S. V.
2016-12-01
NAS RA V. Ambartsumian Byurakan Astrophysical Observatory is presented as a cultural centre for Armenia and the Armenian nation in general. Besides being scientific and educational centre, the Observatory is famous for its unique architectural ensemble, rich botanical garden and world of birds, as well as it is one of the most frequently visited sightseeing of Armenia. In recent years, the Observatory has also taken the initiative of the coordination of the Cultural Astronomy in Armenia and in this field, unites the astronomers, historians, archaeologists, ethnographers, culturologists, literary critics, linguists, art historians and other experts.
NASA Astrophysics Data System (ADS)
Sau, Jay D.; Tewari, Sumanta; Lutchyn, Roman M.; Stanescu, Tudor D.; Das Sarma, S.
2010-12-01
We show that an ordinary semiconducting thin film with spin-orbit coupling can, under appropriate circumstances, be in a quantum topologically ordered state supporting exotic Majorana excitations which follow non-Abelian statistics. The key to the quantum topological order is the coexistence of spin-orbit coupling with proximity-induced s -wave superconductivity and an externally induced Zeeman coupling of the spins. For the Zeeman coupling below a critical value, the system is a nontopological (proximity-induced) s -wave superconductor. However, for a range of Zeeman coupling above the critical value, the lowest energy excited state inside a vortex is a zero-energy Majorana fermion state. The system, thus, has entered into a non-Abelian s -wave superconducting state via a topological quantum phase transition (TQPT) tuned by the Zeeman coupling. In the topological phase, since the time-reversal symmetry is explicitly broken by the Zeeman term in the Hamiltonian, the edge of the film constitutes a chiral Majorana wire. Just like the s -wave superconductivity, the Zeeman coupling can also be proximity induced in the film by an adjacent magnetic insulator. We show this by an explicit model tight-binding calculation for both types of proximity effects in the heterostructure geometry. Here we show that the same TQPT can be accessed by varying the interface transparency between the film and the superconductor. For the transparency below (above) a critical value, the system is a topological (regular) s -wave superconductor. In the one-dimensional version of the same structure and for the Zeeman coupling above the critical value, there are localized Majorana zero-energy modes at the two ends of a semiconducting quantum nanowire. In this case, the Zeeman coupling can be induced more easily by an external magnetic field parallel to the wire, obviating the need for a magnetic insulator. We show that, despite the fact that the superconducting pair potential in the nanowire is
Writing Centre Tutoring Sessions: Addressing Students' Concerns
ERIC Educational Resources Information Center
Winder, Roger; Kathpalia, Sujata S.; Koo, Swit Ling
2016-01-01
The guiding principle behind university writing centres is to focus on the process of writing rather than the finished product, prioritising higher order concerns related to organisation and argumentation of texts rather than lower order concerns of grammar and punctuation. Using survey-based data, this paper examines students' concerns regarding…
Person-Centred (Deictic) Expressions and Autism
ERIC Educational Resources Information Center
Hobson, R. Peter; Garcia-Perez, Rosa M.; Lee, Anthony
2010-01-01
We employed semi-structured tests to determine whether children with autism produce and comprehend deictic (person-centred) expressions such as "this"/"tilde" "here"/"there" and "come"/"go", and whether they understand atypical non-verbal gestural deixis in the form of directed head-nods to indicate location. In Study 1, most participants…
Centre National d'Etudes Spatiales
NASA Astrophysics Data System (ADS)
Murdin, P.
2000-11-01
The Centre National d'Etudes Spatiales (CNES) draws up, proposes and conducts France's space policy. Its role is to develop the uses of space, to meet the civilian and military needs of public bodies and of the scientific community, and to foster the development and dissemination of new applications, designed to create wealth and jobs....
Crystallographic Data Centre Services and Publications.
ERIC Educational Resources Information Center
Cambridge Univ. (England). Chemical Lab.
The Cambridge Crystallographic Data Centre is concerned with the retrieval, evaluation, synthesis, and dissemination of structural data based on diffraction methods. The source of input is almost entirely primary journals. Bibliographic information and numeric data on crystal and molecular structures are on magnetic tapes. The bibliographic file…
Examining Whiteness in a Children's Centre
ERIC Educational Resources Information Center
Clarke, Verity; Watson, Debbie
2014-01-01
This article utilises critical whiteness theory to explore the ethnic discourses observed in a children's centre in South London. Whilst critical whiteness has been used as a framework to understand race, racism and multiculturalism in a number of settings, including education, there are few studies that have sought to understand ethnicity in…
Visiting a science centre: what's on offer?
NASA Astrophysics Data System (ADS)
Russell, Ian
1990-09-01
Science centres are a valuable resource, used more frequently by family groups and primary school parties than by secondary schools. The importance of affective learning, involving attitude changes, is stressed. Provided the right approach is used, accompanying adults can help children get the most out of a visit.
Cactus: The Centres of a Triangle
ERIC Educational Resources Information Center
Hyde, Hartley
2009-01-01
This is the first of two articles which describe how to use "JavaSketchPad" to explore the centres of a triangle. This introductory exercise is suggested in the GSP "Workshop Guide". Students can use "JavaSketchPad Interactive Geometry" (JSP) at home at no cost. They are likely to impress their parents with their enthusiasm for geometry and all…
Oo-Za-We-Kwun Centre Incorporated
ERIC Educational Resources Information Center
Findlay, P. R.; And Others
1976-01-01
The Centre is described as being designed to help native people participate more effectively in a modern Canadian environment. The residential family program includes a five-week Life Skills course followed by a two-year transfer of learning period during which counseling, paid employment, and community activities are available. (Author/MS)
Industry Restructuring: Extracts from Centre Publications.
ERIC Educational Resources Information Center
Hall, William C., Ed.
This document contains excerpts from material previously published by Australia's TAFE (Technical and Further Education) National Centre for Research and Development on the subjects of industry restructuring, the reasons for restructuring, revising curricula, and providing a service to business and industry. Its contents are "Industry…
Self Assessment and Student-Centred Learning
ERIC Educational Resources Information Center
McDonald, Betty
2012-01-01
This paper seeks to show how self assessment facilitates student-centred learning (SCL) and fills a gap in the literature. Two groups of students were selected from a single class in a tertiary educational institution. The control group of 25 was selected randomly by the tossing of an unbiased coin (heads = control group). They were trained in the…
In the Field: The Canadian Ecology Centre.
ERIC Educational Resources Information Center
Magee, Clare
2000-01-01
The Canadian Ecology Centre (Ontario) offers year-round residential and day programs in outdoor and environmental education for secondary students, field placement and internship opportunities for college students, and ecotourism programs, while providing employment and tax revenues to the local community. Dubbed consensus environmentalism, the…
Centring the Subject in Order to Educate
ERIC Educational Resources Information Center
Webster, R. Scott
2007-01-01
It is important for educators to recognise that the various calls to decentre the subject--or self--should not be interpreted as necessarily requiring the removal of the subject altogether. Through the individualism of the Enlightenment the self was centred. This highly individualistic notion of the sovereign self has now been decentred especially…
Myanmar: The Community Learning Centre Experience.
ERIC Educational Resources Information Center
Middelborg, Jorn; Duvieusart, Baudouin, Ed.
A community learning centre (CLC) is a local educational institution outside the formal education system, usually set up and managed by local people. CLCs were first introduced in Myanmar in 1994, and by 2001 there were 71 CLCs in 11 townships. The townships are characterized by remoteness, landlessness, unemployment, dependency on one cash crop,…
Early Childhood Centre Administrator Certification. Project Report.
ERIC Educational Resources Information Center
Ferguson, E. Elaine
This document presents the process for obtaining certification for the position of early childhood centre administrator (ECCA) in Nova Scotia, Canada. Following an introduction describing the development of the process and its pilot testing, Chapter 1 of the document details the four-step process: (1) application, including training in the ECCA…
NASA Astrophysics Data System (ADS)
Chung, Chung-Hou; Sun, Shih-Jye; Chang, Yung-Yeh; Tsai, Wei-Feng; Zhang, Fuchun
Large Hubbard U limit of the Kane-Mele model on a zigzag ribbon of honeycomb lattice near half-filling is studied via a renormalized mean-field theory. The ground state exhibits time-reversal symmetry (TRS) breaking dx2 -y2 + idxy -wave superconductivity. At large spin-orbit coupling, the Z2 topological phase with non-trivial spin Chern number in the pure Kane-Mele model is persistent into the TRS broken state (called ``spin-Chern phase''), and has two pairs of counter-propagating helical Majorana modes at the edges. As the spin-orbit coupling is reduced, the system undergoes a topological quantum phase transition from the spin-Chern to chiral superconducting states. Possible relevance of our results to adatom-doped graphene and irridate compounds is discussed.Ref.:Shih-Jye Sun, Chung-Hou Chung, Yung-Yeh Chang, Wei-Feng Tsai, and Fu-Chun Zhang, arXiv:1506.02584. CHC acknowledges support from NSC Grant No. 98-2918-I-009-06, No. 98-2112-M-009-010-MY3, the NCTU-CTS, the MOE-ATU program, the NCTS of Taiwan, R.O.C.
NASA Astrophysics Data System (ADS)
Su-Xin, Wang; Yu-Xian, Li; Jian-Jun, Liu
2016-03-01
Andreev reflection (AR) in a normal-metal/quantum-dot/superconductor (N-QD-S) system with coupled Majorana bound states (MBSs) is investigated theoretically. We find that in the N-QD-S system, the AR can be enhanced when coupling to the MBSs is incorporated. Fano line-shapes can be observed in the AR conductance spectrum when there is an appropriate QD-MBS coupling or MBS-MBS coupling. The AR conductance is always e2/2h at the zero Fermi energy point when only QD-MBSs coupling is considered. In addition, the resonant AR occurs when the MBS-MBS coupling roughly equals to the QD energy level. We also find that an AR antiresonance appears when the QD energy level approximately equals to the sum of the QD-MBS coupling and the MBS-MBS coupling. These features may serve as characteristic signatures for the probe of MBSs. Project supported by the National Natural Science Foundation of China (Grant Nos. 61176089 and 10974043), the Natural Science Foundation of Hebei Province, China (Grant Nos. A2011205092 and 2014205005), and the Fund for Hebei Normal University for Nationalities, China (Grant No. 201109).
Odd-even effect of transport through a chain of Majorana bound states in a T-shaped junction
NASA Astrophysics Data System (ADS)
Gong, W. J.; Wu, B. H.; Zhang, S. F.; Zheng, Y. S.
2014-05-01
We investigate the transport characteristics of a chain of Majorana bound states (MBSs) in a T-shaped junction, where two normal leads are coupled to the same terminate MBS. We find the apparent odd-even effect in the transport process. Namely, when the MBS number is odd, the conductance spectrum exhibits a peak in the zero-bias limit. Besides, the shot noise Fano factor in the zero-bias limit (F_0) and the conductance maximum (G_{\\textit{max}}) are related by equation F_0=1-{1\\over2}T_{\\textit{max}} with G={e^2\\over h}T . Otherwise, in the case of even-numbered MBSs, at the zero-bias limit, the conductance encounters its zero value, and the relation between F0 and G_{\\textit{max}} changes as F_0=1+{1\\over2}T_{\\textit{max}} . Further investigation shows that these two kinds of relations are caused by the different interplay mechanisms between the crossed Andreev reflection and the local Andreev reflection. In addition, it is observed that the fluctuation of the inter-MBS couplings contributes little to the transport results. We ascertain that these results are helpful for understanding the MBS signature in transport spectra.
NASA Astrophysics Data System (ADS)
Kawakami, Takuto; Hu, Xiao
2015-10-01
In terms of the Bogoliubov-de Gennes approach, we investigate the Majorana bound state (MBS) in a vortex of proximity-induced superconductivity on the surface of a topological insulator. Mapping out the local density of states (LDOS) of quasiparticle excitations as a function of energy and distance from the vortex center, it is found that the spectral distribution evolves from a V shape to a Y shape with the emergence of a MBS upon variation of the chemical potential, consistent with the STM/STS measurement in a very recent experiment [Xu et al., Phys. Rev. Lett. 114, 017001 (2015)] on a Bi2Te3 thin layer on the top of NbSe2 . Moreover, we demonstrate that there is a checkerboard-type pattern in the relative LDOS between the spin-up and -down channels, where the quantum mechanical wave function of the MBS manifests itself clearly as a single quantum state. Therefore, a spin-resolved STM/STS technique is expected to be able to provide phase-sensitive evidence for a MBS in the vortex core of a topological superconductor.
NASA Astrophysics Data System (ADS)
Golub, Anatoly
2015-05-01
We calculate the current as a function of applied voltage in a nontopological s -wave superconductor-quantum dot-topological superconductor (TS) tunnel junction. We consider the type of TS which hosts two Majorana bound states (MBSs) at the ends of a semiconductor quantum wire or of a chain of magnetic atoms in the proximity with an s -wave superconductor. We find that the I -V characteristic of such a system in the regime of big voltages has a typical two-dot shape and is ornamented by peaks of multiple Andreev reflections. We also consider the other options when the zero-energy states are created by disorder (hereby Shiba states) or by Andreev zero-energy bound states at the surface of a quantum dot and a superconductor. The later are obtained by tuning the magnetic field to a specific value. Unlike the last two cases the MBS I -V curves are robust to change the magnetic field. Therefore, the magnetic-field dependence of the tunneling current can serve as a unique signature for the presence of a MBS.
Hui, Hoi-Yin; Brydon, P. M. R.; Sau, Jay D.; Tewari, S.; Sarma, S. Das
2015-01-01
Majorana fermion (MF) excitations in solid state system have non-Abelian statistics which is essential for topological quantum computation. Previous proposals to realize MF, however, generally requires fine-tuning of parameters. Here we explore a platform which avoids the fine-tuning problem, namely a ferromagnetic chain deposited on the surface of a spin-orbit coupled s-wave superconductor. We show that it generically supports zero-energy topological MF excitations near the two ends of the chain with minimal fine-tuning. Depending on the strength of the ferromagnetic moment in the chain, the number of MFs at each end, n, can be either one or two, and should be revealed by a robust zero-bias peak (ZBP) of height 2 ne2/h in scanning tunneling microscopy (STM) measurements which would show strong (weak) signals at the ends (middle) of the chain. The role of an approximate chiral symmetry which gives an integer topological invariant to the system is discussed. PMID:25743763
Few active mechanisms of the 0νββ decay and effective mass of Majorana neutrinos
NASA Astrophysics Data System (ADS)
Šimkovic, Fedor; Vergados, John; Faessler, Amand
2010-12-01
It is well known that there exist many mechanisms that may contribute to neutrinoless double beta decay. By exploiting the fact that the associated nuclear matrix elements are target dependent we show that, given definite experimental results on a sufficient number of targets, one can determine or sufficiently constrain all lepton violating parameters including the mass term. As a specific example we show that, assuming the observation of the 0νββ decay in three different nuclei, e.g., Ge76, Mo100, and Te130, and just three lepton number violating mechanisms (light- and heavy-neutrino mass mechanisms as well as the R-parity breaking supersymmetry mechanism) being active, there are only four different solutions for the lepton violating parameters, provided that they are relatively real. In particular, our analysis shows that the effective neutrino Majorana mass |mββ| can be almost uniquely extracted by utilizing other existing constraints (cosmological observations and tritium β-decay experiments). We also point out the possibility that the nonobservation of the 0νββ decay for some isotopes could be in agreement with a value of |mββ| in the sub-eV region. We thus suggest that it is important to have at least two different 0νββ-decay experiments for a given nucleus. We note that obtained results are sensitive to the accuracy of measured half-lives and to uncertainties in calculated nuclear matrix elements.
Finnerty, P.; Aguayo, Estanislao; Amman, M.; Avignone, Frank T.; Barabash, Alexander S.; Barton, P. J.; Beene, Jim; Bertrand, F.; Boswell, M.; Brudanin, V.; Busch, Matthew; Chan, Yuen-Dat; Christofferson, Cabot-Ann; Collar, J. I.; Combs, Dustin C.; Cooper, R. J.; Detwiler, Jason A.; Doe, P. J.; Efremenko, Yuri; Egorov, Viatcheslav; Ejiri, H.; Elliott, S. R.; Esterline, James H.; Fast, James E.; Fields, N.; Fraenkle, Florian; Galindo-Uribarri, A.; Gehman, Victor M.; Giovanetti, G. K.; Green, M.; Guiseppe, Vincente; Gusey, K.; Hallin, A. L.; Hazama, R.; Henning, Reyco; Hoppe, Eric W.; Horton, Mark; Howard, Stanley; Howe, M. A.; Johnson, R. A.; Keeter, K.; Kidd, M. F.; Knecht, A.; Kochetov, Oleg; Konovalov, S.; Kouzes, Richard T.; LaFerriere, Brian D.; Leon, Jonathan D.; Leviner, L.; Loach, J. C.; Looker, Q.; Luke, P.; MacMullin, S.; Marino, Michael G.; Martin, R. D.; Merriman, Jason H.; Miller, M. L.; Mizouni, Leila; Nomachi, Masaharu; Orrell, John L.; Overman, Nicole R.; Perumpilly, Gopakumar; Phillips, David; Poon, Alan; Radford, D. C.; Rielage, Keith; Robertson, R. G. H.; Ronquest, M. C.; Schubert, Alexis G.; Shima, T.; Shirchenko, M.; Snavely, Kyle J.; Steele, David; Strain, J.; Timkin, V.; Tornow, Werner; Varner, R. L.; Vetter, Kai; Vorren, Kris R.; Wilkerson, J. F.; Yakushev, E.; Yaver, Harold; Young, A.; Yu, Chang-Hong; Yumatov, Vladimir
2014-03-24
The Majorana Demonstrator will search for the neutrinoless double-beta decay (0*) of the 76Ge isotope with a mixed array of enriched and natural germanium detectors. The observation of this rare decay would indicate the neutrino is its own anti-particle, demonstrate that lepton number is not conserved, and provide information on the absolute mass-scale of the neutrino. The Demonstrator is being assembled at the 4850 foot level of the Sanford Underground Research Facility in Lead, South Dakota. The array will be contained in a lowbackground environment and surrounded by passive and active shielding. The goals for the Demonstrator are: demonstrating a background rate less than 3 counts tonne -1 year-1 in the 4 keV region of interest (ROI) surrounding the 2039 keV 76Ge endpoint energy; establishing the technology required to build a tonne-scale germanium based double-beta decay experiment; testing the recent claim of observation of 0; and performing a direct search for lightWIMPs (3-10 GeV/c2).
An MCMC-based waveform analysis with p-type point contact detectors in the MAJORANA DEMONSTRATOR
NASA Astrophysics Data System (ADS)
Shanks, Benjamin; MAJORANA Collaboration
2017-01-01
Statistical signal processing can be a powerful tool for extracting as much information as possible from raw data. By fitting data to a physical model of signal generation on an event-by-event basis, it can be used to perform precise event reconstruction and enable efficient background rejection. Searches for neutrinoless double-beta decay must achieve extremely low backgrounds to reach sensitivities required for discovery, and so can benefit greatly from this analysis technique. The MAJORANA DEMONSTRATOR has implemented a Markov Chain Monte Carlo (MCMC) signal processing algorithm to fit waveforms from p-type point contact (PPC) germanium detectors. After a machine learning step to tune detector fields and electronics response parameters, the MCMC algorithm is able to reconstruct the time, energy and position of interactions within the PPC detector. The parameters estimated with this method will find many applications within the DEMONSTRATOR physics program, including background identification and rejection. This will prove important as the DEMONSTRATOR aims to reach its background goal of < 3 counts/tonne/yr in the region of interest. This work is supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics, the Particle Astrophysics and Nuclear Physics Programs of the National Science Foundation, and the Sanford Underground Research Facility.
Collaborating at a distance: operations centres, tools, and trends
Gottschalk, Erik E.; /Fermilab
2009-05-01
Successful operation of the LHC and its experiments is crucial to the future of the worldwide high-energy physics program. Remote operations and monitoring centres have been established for the CMS experiment in several locations around the world. The development of remote centres began with the LHC{at}FNAL ROC and has evolved into a unified approach with distributed centres that are collectively referred to as 'CMS Centres Worldwide'. An overview of the development of remote centres for CMS will be presented, along with a synopsis of collaborative tools that are used in these centres today and trends in the development of remote operations capabilities for high-energy physics.
User-Centred Design Using Gamestorming.
Currie, Leanne
2016-01-01
User-centered design (UX) is becoming a standard in software engineering and has tremendous potential in healthcare. The purpose of this tutorial will be to demonstrate and provide participants with practice in user-centred design methods that involve 'Gamestorming', a form of brainstorming where 'the rules of life are temporarily suspended'. Participants will learn and apply gamestorming methods including persona development via empathy mapping and methods to translate artefacts derived from participatory design sessions into functional and design requirements.
Mossa, Abdel-Tawab H.; Refaie, Amel A.; Ramadan, Amal; Bouajila, Jalloul
2013-01-01
This study was carried out to evaluate the adverse effects of exposure to prallethrin on oxidant/antioxidant status and liver dysfunction biomarkers and the protective role of Origanum majorana essential oil (EO) in rat. Male rats were divided into 4 groups: (i) received only olive oil (ii) treated with 64.0 mg/kg body weight prallethrin (1/10 LD50) in olive oil via oral route daily for 28 days, (iii) treated with 64.0 mg/kg body weight prallethrin (1/10 LD50) and EO (160 μL/kg b.wt.) in olive oil and (iv) received EO (160 μL/kg b.wt.) in olive oil via oral route twice daily for 28 days. Prallethrin treatment caused decrease in body weight gain and increase in relative liver weight. There was a significant increase in the activity of serum marker enzymes, aspartate transaminase, alanine transaminase, and alkaline phosphatase. It caused increase in thiobarbituric acid reactive substances and reduction in the activities of superoxide dismutase, catalase, and glutathione-S-transferase in liver. Consistent histological changes were found in the liver of prallethrin treatment. EO showed significant protection with the depletion of serum marker enzymes and replenishment of antioxidant status and brought all the values to near normal, indicating the protective effect of EO. We can conclude that prallethrin caused oxidative damage and liver injury in male rat and co-administration of EO attenuated the toxic effect of prallethrin. These results demonstrate that administration of EO may be useful, easy, and economical to protect human against pyrethroids toxic effects. PMID:24381944
Canadian Educational Development Centre Websites: More Ebb than Flow?
ERIC Educational Resources Information Center
Simmons, Nicola
2010-01-01
This paper examines information portrayed on Canadian educational development (ED) centre websites and, in particular, whether information that corresponds to questions compiled from a literature search of ED centre practices is readily available from centre websites. This study phase is part of a larger national study of Canadian educational…
Centre of the Cell: Science Comes to Life
Balkwill, Frances; Chambers, Katie
2015-01-01
Centre of the Cell is a unique biomedical science education centre, a widening participation and outreach project in London’s East End. This article describes Centre of the Cell’s first five years of operation, the evolution of the project in response to audience demand, and the impact of siting a major public engagement project within a research laboratory. PMID:26340279
Centre-Based Child Care Quality in Urban Australia
ERIC Educational Resources Information Center
Ishimine, Karin; Wilson, Rachel
2009-01-01
This study investigates the quality of childcare centres in urban Australian communities designated according to different bands of Centre Location Demographics (CLD). Childcare centres were assessed using the Early Childhood Environment Rating Scale- Revised Edition (ECERS-R) and the Early Childhood Environment Rating Scale-Extension (ECERS-E).…
Assessment of functional incontinence in disabled living centres.
Chadwick, Viv
Disabled Living is part of the network of disabled living centres throughout Britain. These centres enable anyone to try out equipment that may help them with everyday activities of living. The centres are staffed by occupational therapists, physiotherapists, nurses, information providers, administration staff and volunteers.
ERIC Educational Resources Information Center
Koh, Aaron
2014-01-01
Why do more than three-quarters of Hong Kong's senior secondary students flock to tutorial centres like moths to light? What is the "magic" that is driving the popularity of the tutorial centre enterprise? Indeed, looking at the ongoing boom of tutorial centres in Hong Kong (there are almost 1,000 of them), it is difficult not to ask…
Human-centred approaches in slipperiness measurement
Grönqvist, Raoul; Abeysekera, John; Gard, Gunvor; Hsiang, Simon M.; Leamon, Tom B.; Newman, Dava J.; Gielo-Perczak, Krystyna; Lockhart, Thurmon E.; Pai, Clive Y.-C.
2010-01-01
A number of human-centred methodologies—subjective, objective, and combined—are used for slipperiness measurement. They comprise a variety of approaches from biomechanically-oriented experiments to psychophysical tests and subjective evaluations. The objective of this paper is to review some of the research done in the field, including such topics as awareness and perception of slipperiness, postural and balance control, rating scales for balance, adaptation to slippery conditions, measurement of unexpected movements, kinematics of slipping, and protective movements during falling. The role of human factors in slips and falls will be discussed. Strengths and weaknesses of human-centred approaches in relation to mechanical slip test methodologies are considered. Current friction-based criteria and thresholds for walking without slipping are reviewed for a number of work tasks. These include activities such as walking on a level or an inclined surface, running, stopping and jumping, as well as stair ascent and descent, manual exertion (pushing and pulling, load carrying, lifting) and particular concerns of the elderly and mobility disabled persons. Some future directions for slipperiness measurement and research in the field of slips and falls are outlined. Human-centred approaches for slipperiness measurement do have many applications. First, they are utilized to develop research hypotheses and models to predict workplace risks caused by slipping. Second, they are important alternatives to apparatus-based friction measurements and are used to validate such methodologies. Third, they are used as practical tools for evaluating and monitoring slip resistance properties of foot wear, anti-skid devices and floor surfaces. PMID:11794763
Hunting for hardware changes in data centres
NASA Astrophysics Data System (ADS)
Coelho dos Santos, M.; Steers, I.; Szebenyi, I.; Xafi, A.; Barring, O.; Bonfillou, E.
2012-12-01
With many servers and server parts the environment of warehouse sized data centres is increasingly complex. Server life-cycle management and hardware failures are responsible for frequent changes that need to be managed. To manage these changes better a project codenamed “hardware hound” focusing on hardware failure trending and hardware inventory has been started at CERN. By creating and using a hardware oriented data set - the inventory - with detailed information on servers and their parts as well as tracking changes to this inventory, the project aims at, for example, being able to discover trends in hardware failure rates.
WISB: Warwick Integrative Synthetic Biology Centre
McCarthy, John
2016-01-01
Synthetic biology promises to create high-impact solutions to challenges in the areas of biotechnology, human/animal health, the environment, energy, materials and food security. Equally, synthetic biologists create tools and strategies that have the potential to help us answer important fundamental questions in biology. Warwick Integrative Synthetic Biology (WISB) pursues both of these mutually complementary ‘build to apply’ and ‘build to understand’ approaches. This is reflected in our research structure, in which a core theme on predictive biosystems engineering develops underpinning understanding as well as next-generation experimental/theoretical tools, and these are then incorporated into three applied themes in which we engineer biosynthetic pathways, microbial communities and microbial effector systems in plants. WISB takes a comprehensive approach to training, education and outreach. For example, WISB is a partner in the EPSRC/BBSRC-funded U.K. Doctoral Training Centre in synthetic biology, we have developed a new undergraduate module in the subject, and we have established five WISB Research Career Development Fellowships to support young group leaders. Research in Ethical, Legal and Societal Aspects (ELSA) of synthetic biology is embedded in our centre activities. WISB has been highly proactive in building an international research and training network that includes partners in Barcelona, Boston, Copenhagen, Madrid, Marburg, São Paulo, Tartu and Valencia. PMID:27284024
KNMI Data Centre: Easy access for all
NASA Astrophysics Data System (ADS)
van de Vegte, John; Som de Cerff, Wim; Plieger, Maarten; de Vreede, Ernst; Sluiter, Raymond; Willem Noteboom, Jan; van der Neut, Ian; Verhoef, Hans; van Versendaal, Robert; van Binnendijk, Martin; Kalle, Henk; Knopper, Arthur; Spit, Jasper; Mastop, Joeri; Klos, Olaf; Calis, Gijs; Ha, Siu-Siu; van Moosel, Wim; Klein Ikkink, Henk-Jan; Tosun, Tuncay
2013-04-01
KNMI is the Dutch institute for weather, climate research and seismology. It disseminates weather information to the public at large, the government, aviation and the shipping industry in the interest of safety, the economy and a sustainable environment. To gain insight into long-term developments KNMI conducts research on climate change. Making the knowledge, data and information on hand at KNMI accessible is one core activity. A huge part of the KNMI information is from numerical models, insitu sensor networks and remote sensing satellites. This digital collection is mostly internal only available and is a collection of non searchable , non standardized file formats, lacking documentation and has no references to scientific publications. With the KNMI Data Centre (KDC) project these issues are tackled. In the project a user driven development approach with SCRUM was chosen to get maximum user involvement in a relative short development timeframe. Building on open standards and proven open source technology (which includes in-house developed software like ADAGUC WMS and Portal) resulted in a first release in December 2012 This presentation will focus on the aspects of KDC relating to its technical challenges, the development strategy and the initial usage results of the data centre.
Spherical tokamaks with plasma centre-post
NASA Astrophysics Data System (ADS)
Ribeiro, Celso
2013-10-01
The metal centre-post (MCP) in tokamaks is a structure which carries the total toroidal field current and also houses the Ohmic heating solenoid in conventional or low aspect ratio (Spherical)(ST) tokamaks. The MCP and solenoid are critical components for producing the toroidal field and for the limited Ohmic flux in STs. Constraints for a ST reactor related to these limitations lead to a minimum plasma aspect ratio of 1.4 which reduces the benefit of operation at higher betas in a more compact ST reactor. Replacing the MCP is of great interest for reactor-based ST studies since the device is simplified, compactness increased, and maintenance reduced. An experiment to show the feasibility of using a plasma centre-post (PCP) is being currently under construction and involves a high level of complexity. A preliminary study of a very simple PCP, which is ECR(Electron Cyclotron Resonance)-assisted and which includes an innovative fuelling system based on pellet injection, has recently been reported. This is highly suitable for an ultra-low aspect ratio tokamak (ULART) device. Advances on this PCP ECR-assisted concept within a ULART and the associated fuelling system are presented here, and will include the field topology for the PCP ECR-assisted scheme, pellet ablation modeling, and a possible global equilibrium simulation. VIE-ITCR, IAEA-CRP contr.17592, National Instruments-Costa Rica.
Sofia University GNSS Analysis Centre (SUGAC)
NASA Astrophysics Data System (ADS)
Simeonov, Tzvetan; Sidorov, Dmitry; Teferle, Norman; Guerova, Guergana; Egova, Evgenia; Vassileva, Keranka; Milev, Ivo; Milev, Georgi
2015-04-01
The Sofia University GNSS Analysis Centre (SUGAC, suada.phys.uni-sofia.bg) is a new analysis centre established via collaboration between the Department of Meteorology and Geophysics of Sofia University, the IPOS - BuliPOS GNSS network in Bulgaria and the University of Luxembourg. In April 2014, the first processing campaign took place. One year GNSS data from 7 stations of the BuliPOS network are processed in collaboration with the University of Luxembourg. Tropospheric products (Zenith Total Delay and gradients) with 5 min temporal resolution are obtained using the NAPEOS software, developed by ESA. The tropospheric products from this campaign will be used for validation of the Weather Research and Forecasting (WRF) model as well as for case studies during intense precipitation events and fog. In this work the WRF model validation for Bulgaria will be presented. Future work will be the establishment of autonomous near real-time processing of the regional ground-based GNSS network in Southeast Europe in support of the EUMETNET E-GVAP and COST ES1206 "Advanced Global Navigation Satellite Systems for Severe Weather Events and Climate" projects.
NASA Astrophysics Data System (ADS)
Hilderbrand, S.; Kwan, E.; Angell, C.; Fallin, B.; Howell, C. R.; Hutcheson, A.; Karwowski, H. J.; Kelley, J. H.; Tonchev, A. P.; Tornow, W.; Masters, D. B.; Pedroni, R. S.; Weisel, G. J.
2007-10-01
The goal of the Majorana Collaboration is to study 0νββ in order to verify that the neutrino is its own anti-particle; and if so, what is the mass ofthe electron neutrino. Observation of a sharp peak at the ββ endpoint energy will confirm 0νββ as a decay mode, and determination of the partial width will determine the matrix element which depends directly on the electron neutrino mass. In order to observe and verify the existence of 0νββ, it is important to reduce intrinsic, extrinsic,& cosmogenic backgrounds. The Majorana Project will operate with HPGe detectors deep underground to achieve a low-background environment. Recent advances in signal processing and detector design have also enabled scientists to further understand background sources. γ-ray spectra from the interaction of pulsed mono-energetic neutrons with ^76Ge were measured at TUNL using segmented HPGe clover detectors. The neutron-induced partial cross-sections for γ transitions in ^76Ge were measured at En = 8 and 12MeV.
Sun, Shih-Jye; Chung, Chung-Hou; Chang, Yung-Yeh; Tsai, Wei-Feng; Zhang, Fu-Chun
2016-04-11
There has been growing interest in searching for exotic self-conjugate, charge-neutral low-energy fermionic quasi-particles, known as Majorana fermions (MFs) in solid state systems. Their signatures have been proposed and potentially observed at edges of topological superconcuctors with non-trivial topological invariant in the bulk electronic band structure. Much effort have been focused on realizing MFs in odd-parity superconductors made of strong spin-orbit coupled materials in proximity to conventional superconductors. In this paper, we propose a novel mechanism for realizing MFs in 2D spin-singlet topological superconducting state induced by doping a correlated quantum spin Hall (Kane-Mele) insulator. Via a renormalized mean-field approach, the system is found to exhibits time-reversal symmetry (TRS) breaking d(x2-y2) + id(xy)-wave (chiral d-wave) superconductivity near half-filling in the limit of large on-site repulsion. Surprisingly, however, at large spin-orbit coupling, the system undergoes a topological phase transition and enter into a new topological phase protected by a pseudo-spin Chern number, which can be viewed as a persistent extension of the quantum spin Hall phase upon doping. From bulk-edge correspondence, this phase is featured by the presence of two pairs of counter-propagating helical Majorana modes per edge, instead of two chiral propagating edge modes in the d + id' superconductors.
ERIC Educational Resources Information Center
Wade, Catherine M.; Mildon, Robyn L.; Matthews, Jan M.
2007-01-01
Background: Studies support the use of family-centred practices in service delivery to families where a parent has an intellectual disability. This paper examines the importance of such practices to parents. Materials and Methods: Interview responses from 32 parents with intellectual disability were coded by two independent raters as reflecting…
The Curriculum Development Centre of Malaysia. Studies of Curriculum Development Centres in Asia 2.
ERIC Educational Resources Information Center
Oon-Chye, Yeoh; And Others
The Curriculum Development Centre (CDC) of Malaysia became an operating agency in January 1973 and became a division of the Malaysia Ministry of Education in May 1974. Its establishment was the culmination of over a decade of curriculum development efforts by the Ministry of Education. The CDC was an outgrowth of both the First and Second Malaysia…
ERIC Educational Resources Information Center
Forrest, Gregory
2015-01-01
Background: Game-centred approaches (GCA) have been promoted as a more meaningful way to teach games and sports due to their connections with constructivist learning principles. However, the implementation is dependant on the teacher implementing it rather than just the model. There has been little research into what it means to use a GCA well and…
NASA Astrophysics Data System (ADS)
Nefedjev, Yu. A.; Valeev, S. G.; Rizvanov, N. G.; Mikeev, R. R.; Varaksina, N. Yu.
2010-05-01
The relative position of lunar center masses relative to center of the figure in Kazan and Kiev selenocentric catalogues was customized. The expansions by spherical harmonics N=5 degree and order of the lunar function h(λ, β) with using the package ASNI USTU were executed. Module of the expansion of the local area to surfaces to full sphere was used. The parameters of cosmic missions are given for comparison (SAI; Bills, Ferrari). The normalized coefficients from expansions for eight sources hypsometric information are obtained: - Clementine (N=40), - Kazan (N=5), - Kiev (N=5), - SAI (N=10; Chuikova (1975)), - Bills, Ferrari, - Каguуа (Selena, Japan mission), - ULCN (The Uuified Lunaz Control Network 2005). The displacements of the lunar centre figure relative to lunar centre of the masses were defined from equations (Chuikova (1975)). The results of the obtaining relative position of the lunar centre masses and centre of the figure in Kazan selenocentric catalogue give good agreement with modern cosmic mission data.
Quantum transport through a multi-quantum-dot-pair chain side-coupled with Majorana bound states
NASA Astrophysics Data System (ADS)
Zhao-Tan, Jiang; Cheng-Cheng, Zhong
2016-06-01
We investigate the quantum transport properties through a special kind of quantum dot (QD) system composed of a serially coupled multi-QD-pair (multi-QDP) chain and side-coupled Majorana bound states (MBSs) by using the Green functions method, where the conductance can be classified into two kinds: the electron tunneling (ET) conductance and the Andreev reflection (AR) one. First we find that for the nonzero MBS-QDP coupling a sharp AR-induced zero-bias conductance peak with the height of e 2/h is present (or absent) when the MBS is coupled to the far left (or the other) QDP. Moreover, the MBS-QDP coupling can suppress the ET conductance and strengthen the AR one, and further split into two sub-peaks each of the total conductance peaks of the isolated multi-QDPs, indicating that the MBS will make obvious influences on the competition between the ET and AR processes. Then we find that the tunneling rate Γ L is able to affect the conductances of leads L and R in different ways, demonstrating that there exists a Γ L-related competition between the AR and ET processes. Finally we consider the effect of the inter-MBS coupling on the conductances of the multi-QDP chains and it is shown that the inter-MBS coupling will split the zero-bias conductance peak with the height of e 2/h into two sub-peaks. As the inter-MBS coupling becomes stronger, the two sub-peaks are pushed away from each other and simultaneously become lower, which is opposite to that of the single QDP chain where the two sub-peaks with the height of about e 2/2h become higher. Also, the decay of the conductance sub-peaks with the increase of the MBS-QDP coupling becomes slower as the number of the QDPs becomes larger. This research should be an important extension in studying the transport properties in the kind of QD systems coupled with the side MBSs, which is helpful for understanding the nature of the MBSs, as well as the MBS-related QD transport properties. Project supported by the National Natural
Children's Centre "3 in 1 - together"
NASA Astrophysics Data System (ADS)
Gancheva, Hristina
2013-04-01
"There are only two ways to life your live. One is as though nothing is a miracle. The other is as though everything is a miracle." Albert Einstein Children's Centre "3 in 1" is an extracurricular unit linked to the High School of Zlatartitsa, St. Cyril and St. Methodius, accomplished with the help of the municipality and many volunteers from the local community. With its activity it forms in children patriotic spirit, love for nature, active citizenship, and an impulse for a healthy life through communication with nature, saving the traditions and history, insurance of equality of the kids of the local five ethnicities and participation in activities in the sphere of science, art, sport and tourism. The educational work is mainly directed towards kids with difficulties with communication, hyperactivity, aggression, problems in their families, or those deprived of parental care. For a few years in the Children's Centre there have been clubs of interests: "Gardeners" - kids cultivate a garden. They plow, dig, plant, put in, irrigate and weed under the watch of Ms Stafka Nikolova, parents, and volunteers of the local community. The ecologically clean products - vegetables and fruits, kids use to cook delicious meals, sell, or give away. Weeds are also utilized; they are making herbarium out of them. "Cooks" - "What to have for lunch, when mom is out?". One can learn a lot of wonderful recipes from the club "Cooks". Products are own made, raised with love. In 2010, on the on the annual traditional holiday of the garden soup in Zlataritsa, the little cooks won third prize for making a delicious vegetable soup. On the same day, the 26 years old Nadezhda Savova, Cultural and Social Anthropology PhD in Princeton, founded the second community bakery in Bulgaria in Children's Centre "3 in1". Nadezhda Savova was declared traveler of 2012 by National Geographic. After the baking house in Gabrovo and Zlataritsa, Nadezhda also founded such projects in Sofia, Varna and Ruse
Initial experience with an Underwater Manifold Centre
Osborne, J.M.
1984-10-01
In July 1983 comingled production from the first two completed wells of the Shell/Esso Underwater Manifold Centre (the UMC), reached the Cormorant Alpha platform. This moment was the culmination of design and development effort which had begun as early as the spring of 1975. But being both the largest subsea system to become operational in the North Sea, and the first designed to the production of several subsea wells, whilst injecting into others, how would the UMC continue to perform. This paper details the operational experience gained to date with the UMC, tracing its brief history since it was first powered up in September 1982 to the present. This is discussed in the main body of the paper under the headings: Commissioning Experience; Operating Experience; Reliability and Maintenance.
PRICE: primitive centred schemes for hyperbolic systems
NASA Astrophysics Data System (ADS)
Toro, E. F.; Siviglia, A.
2003-08-01
We present first- and higher-order non-oscillatory primitive (PRI) centred (CE) numerical schemes for solving systems of hyperbolic partial differential equations written in primitive (or non-conservative) form. Non-conservative systems arise in a variety of fields of application and they are adopted in that form for numerical convenience, or more importantly, because they do not posses a known conservative form; in the latter case there is no option but to apply non-conservative methods. In addition we have chosen a centred, as distinct from upwind, philosophy. This is because the systems we are ultimately interested in (e.g. mud flows, multiphase flows) are exceedingly complicated and the eigenstructure is difficult, or very costly or simply impossible to obtain. We derive six new basic schemes and then we study two ways of extending the most successful of these to produce second-order non-oscillatory methods. We have used the MUSCL-Hancock and the ADER approaches. In the ADER approach we have used two ways of dealing with linear reconstructions so as to avoid spurious oscillations: the ADER TVD scheme and ADER with ENO reconstruction. Extensive numerical experiments suggest that all the schemes are very satisfactory, with the ADER/ENO scheme being perhaps the most promising, first for dealing with source terms and secondly, because higher-order extensions (greater than two) are possible. Work currently in progress includes the application of some of these ideas to solve the mud flow equations. The schemes presented are generic and can be applied to any hyperbolic system in non-conservative form and for which solutions include smooth parts, contact discontinuities and weak shocks. The advantage of the schemes presented over upwind-based methods is simplicity and efficiency, and will be fully realized for hyperbolic systems in which the provision of upwind information is very costly or is not available.
Distant Operational Care Centre: Design Project Report
NASA Technical Reports Server (NTRS)
1996-01-01
The goal of this project is to outline the design of the Distant Operational Care Centre (DOCC), a modular medical facility to maintain human health and performance in space, that is adaptable to a range of remote human habitats. The purpose of this project is to outline a design, not to go into a complete technical specification of a medical facility for space. This project involves a process to produce a concise set of requirements, addressing the fundamental problems and issues regarding all aspects of a space medical facility for the future. The ideas presented here are at a high level, based on existing, researched, and hypothetical technologies. Given the long development times for space exploration, the outlined concepts from this project embodies a collection of identified problems, and corresponding proposed solutions and ideas, ready to contribute to future space exploration efforts. In order to provide a solid extrapolation and speculation in the context of the future of space medicine, the extent of this project's vision is roughly within the next two decades. The Distant Operational Care Centre (DOCC) is a modular medical facility for space. That is, its function is to maintain human health and performance in space environments, through prevention, diagnosis, and treatment. Furthermore, the DOCC must be adaptable to meet the environmental requirements of different remote human habitats, and support a high quality of human performance. To meet a diverse range of remote human habitats, the DOCC concentrates on a core medical capability that can then be adapted. Adaptation would make use of the DOCC's functional modularity, providing the ability to replace, add, and modify core functions of the DOCC by updating hardware, operations, and procedures. Some of the challenges to be addressed by this project include what constitutes the core medical capability in terms of hardware, operations, and procedures, and how DOCC can be adapted to different remote
Common Myna Roosts Are Not Recruitment Centres
Sarangi, Manaswini; Arvind, Chiti; Lakshman, Abhilash; Vidya, T. N. C.
2014-01-01
We studied communal roosting in the Common Myna (Acridotheres tristis) in the light of the recruitment centre hypothesis and predation at the roost. The number and sizes of flocks departing from and arriving at focal roosts were recorded over a two year period. We also recorded the sizes and behaviour of foraging flocks. We found that flock sizes of birds departing from roosts at sunrise were larger than those at the feeding site, suggesting that there was no recruitment from the roosts. Flocks entering the roosts during sunset were larger on average than those leaving the following sunrise, suggesting no consolidation of flocks in the morning. Flocks entering the roosts at sunset were also larger on average than those that had left that sunrise, although there was no recruitment at the feeding site. There was no effect of group size on the proportion of time spent feeding. Contrary to expectation, single birds showed lower apparent vigilance than birds that foraged in pairs or groups, possibly due to scrounging tactics being used in the presence of feeding companions. Thus, the recruitment centre hypothesis did not hold in our study population of mynas. Predation at dawn and dusk were also not important to communal roosting: predators near the roosts did not result in larger flocks, and resulted in larger durations of arrival/departure contrary to expectation. Since flock sizes were smallest at the feeding site and larger in the evening than in the morning, but did not coincide with predator activity, information transfer unrelated to food (such as breeding opportunities) may possibly give rise to the evening aggregations. PMID:25122467
The Centre of Mass of a Triangular Plate
ERIC Educational Resources Information Center
Slusarenko, Viktor; Rojas, Roberto; Fuster, Gonzalo
2008-01-01
We present a derivation for the coordinates of the centre of mass--or centre of gravity--of a homogeneous triangular plate by using scaling and symmetry. We scale the triangular plate by a factor of 2 and divide its area into four plates identical to the original. By symmetry, we assert that the centre of mass of two identical masses lies at the…
Complex Modelling Scheme Of An Additive Manufacturing Centre
NASA Astrophysics Data System (ADS)
Popescu, Liliana Georgeta
2015-09-01
This paper presents a modelling scheme sustaining the development of an additive manufacturing research centre model and its processes. This modelling is performed using IDEF0, the resulting model process representing the basic processes required in developing such a centre in any university. While the activities presented in this study are those recommended in general, changes may occur in specific existing situations in a research centre.