Anomalous aharonov-bohm gap oscillations in carbon nanotubes.
Sangalli, Davide; Marini, Andrea
2011-10-12
The gap oscillations caused by a magnetic flux penetrating a carbon nanotube represent one of the most spectacular observations of the Aharonov-Bohm effect at the nanoscale. Our understanding of this effect is, however, based on the assumption that the electrons are strictly confined on the tube surface, on trajectories that are not modified by curvature effects. Using an ab initio approach based on density functional theory, we show that this assumption fails at the nanoscale inducing important corrections to the physics of the Aharonov-Bohm effect. Curvature effects and electronic density that is spilled out of the nanotube surface are shown to break the periodicity of the gap oscillations. We predict the key phenomenological features of this anomalous Aharonov-Bohm effect in semiconductive and metallic tubes and the existence of a large metallic phase in the low flux regime of multiwalled nanotubes, also suggesting possible experiments to validate our results.
Quantum chaos in Aharonov-Bohm oscillations
Berman, G.P.; Campbell, D.K.; Bulgakov, E.N.; Krive, I.V.
1995-10-01
Aharonov-Bohm oscillations in a mesoscopic ballistic ring are considered under the influence of a resonant magnetic field with one and two frequencies. The authors investigate the oscillations of the time-averaged electron energy at zero temperature in the regime of an isolated quantum nonlinear resonance and at the transition to quantum chaos, when two quantum nonlinear resonances overlap. It is shown that the time-averaged energy exhibits resonant behavior as a function of the magnetic flux, and has a ``staircase`` dependence on the amplitude of the external field. The delocalization of the quasi-energy eigenfunctions is analyzed.
Patterns of the Aharonov-Bohm oscillations in graphene nanorings
NASA Astrophysics Data System (ADS)
Romanovsky, Igor; Yannouleas, Constantine; Landman, Uzi
2012-04-01
Using extensive tight-binding calculations, we investigate (including the spin) the Aharonov-Bohm (AB) effect in monolayer and bilayer trigonal and hexagonal graphene rings with zigzag boundary conditions. Unlike the previous literature, we demonstrate the universality of integer (hc/e) and half-integer (hc/2e) values for the period of the AB oscillations as a function of the magnetic flux, in consonance with the case of mesoscopic metal rings. Odd-even (in the number of Dirac electrons, N) sawtooth-type patterns relating to the halving of the period have also been found; they are more numerous for a monolayer hexagonal ring, compared to the cases of a trigonal and a bilayer hexagonal ring. Additional, more complicated patterns are also present, depending on the shape of the graphene ring. Overall, the AB patterns repeat themselves as a function of N, with periods proportional to the number of the sides of the rings.
Aharonov-Bohm oscillations in singly connected disordered conductors.
Aleiner, I L; Andreev, A V; Vinokur, V
2015-02-20
We show that the transport and thermodynamic properties of a singly connected disordered conductor exhibit quantum Aharonov-Bohm oscillations as a function of the total magnetic flux through the sample. The oscillations are associated with the interference contribution from a special class of electron trajectories confined to the surface of the sample.
Spin-selective Aharonov-Bohm oscillations in a lateral triple quantum dot.
Delgado, F; Shim, Y-P; Korkusinski, M; Gaudreau, L; Studenikin, S A; Sachrajda, A S; Hawrylak, P
2008-11-28
We present a theory of spin-selective Aharonov-Bohm oscillations in a lateral triple quantum dot. We show that to understand the Aharonov-Bohm (AB) effect in an interacting electron system within a triple quantum dot molecule (TQD) where the dots lie in a ring configuration requires one to not only consider electron charge but also spin. Using a Hubbard model supported by microscopic calculations we show that, by localizing a single electron spin in one of the dots, the current through the TQD molecule depends not only on the flux but also on the relative orientation of the spin of the incoming and localized electrons. AB oscillations are predicted only for the spin singlet electron complex resulting in a magnetic field tunable "spin valve."
Aharonov-Bohm oscillations in the presence of strong spin-orbit interactions.
Grbić, Boris; Leturcq, Renaud; Ihn, Thomas; Ensslin, Klaus; Reuter, Dirk; Wieck, Andreas D
2007-10-26
We have measured highly visible Aharonov-Bohm (AB) oscillations in a ring structure defined by local anodic oxidation on a p-type GaAs heterostructure with strong spin-orbit interactions. Clear beating patterns observed in the raw data can be interpreted in terms of a spin geometric phase. Besides h/e oscillations, we resolve the contributions from the second harmonic of AB oscillations and also find a beating in these h/2e oscillations. A resistance minimum at B=0 T, present in all gate configurations, is the signature of destructive interference of the spins propagating along time-reversed paths.
Polarization and Aharonov-Bohm oscillations in quantum-ring magnetoexcitons
Dias da Silva, Luis G.G.V.; Ulloa, Sergio E.; Shahbazyan, Tigran V.
2005-09-15
We study interaction and radial polarization effects on the absorption spectrum of neutral bound magnetoexcitons confined in quantum-ring structures. We show that the size and orientation of the exciton's dipole moment, as well as the interaction screening, play important roles in the Aharonov-Bohm (AB) oscillations. In particular, the excitonic absorption peaks display AB oscillations both in position and amplitude for weak electron-hole interaction and large radial polarization. The presence of impurity scattering induces anticrossings in the exciton spectrum, leading to a modulation in the absorption strength. These properties could be used in experimental investigations of the effect in semiconductor quantum-ring structures.
h/2 e Oscillations and negative magneto-resistance in ballistic chaotic Aharonov-Bohm billiards
NASA Astrophysics Data System (ADS)
Kawabata, Shiro; Nakamura, Katsuhiro
1998-07-01
We study the quantum-interference effect for the single ballistic Aharonov-Bohm (AB) billiard. The reflection coefficient δRD is calculated by use of semi-classical scattering theory. We find: (i) h/2 e Altshuler-Aronov-Spivak (AAS) oscillation is experimentally observable in both ballistic and diffusive systems; (ii) a magnetic field in the conducting region leads to "negative magneto-resistance" and "dampening of the AAS oscillation amplitude". Chaotic and regular AB billiards have turned out to lead to qualitatively different semi-classical formulas for conductance with their behavior determined only by knowledge regarding the underlying classical scattering.
Aharonov-Bohm oscillations in disordered topological insulator nanowires.
Bardarson, J H; Brouwer, P W; Moore, J E
2010-10-08
A direct signature of electron transport at the metallic surface of a topological insulator is the Aharonov-Bohm oscillation observed in a recent study of Bi2Se3 nanowires [Peng, Nature Mater. 9, 225 (2010)] where conductance was found to oscillate as a function of magnetic flux ϕ through the wire, with a period of one flux quantum ϕ0=h/e and maximum conductance at zero flux. This seemingly agrees neither with diffusive theory, which would predict a period of half a flux quantum, nor with ballistic theory, which in the simplest form predicts a period of ϕ0 but a minimum at zero flux due to a nontrivial Berry phase in topological insulators. We show how h/e and h/2e flux oscillations of the conductance depend on doping and disorder strength, provide a possible explanation for the experiments, and discuss further experiments that could verify the theory.
Anomalous Aharonov-Bohm conductance oscillations from topological insulator surface states.
Zhang, Yi; Vishwanath, Ashvin
2010-11-12
We study Aharonov-Bohm (AB) conductance oscillations arising from the surface states of a topological insulator nanowire, when a magnetic field is applied along its length. With strong surface disorder, these oscillations are predicted to have a component with anomalous period Φ(0)=hc/e, twice the conventional period. The conductance maxima are achieved at odd multiples of 1/2Φ(0), implying that a π AB phase for electrons strengthens the metallic nature of surface states. This effect is special to topological insulators, and serves as a defining transport property. A key ingredient, the surface curvature induced Berry phase, is emphasized here. We discuss similarities and differences from recent experiments on Bi2Se3 nanoribbons, and optimal conditions for observing this effect.
Dephasing by extremely dilute magnetic impurities revealed by Aharonov-Bohm oscillations.
Pierre, F; Birge, Norman O
2002-11-11
We have probed the magnetic field dependence of the electron phase coherence time tau(phi) by measuring the Aharonov-Bohm conductance oscillations of mesoscopic Cu rings. Whereas tau(phi) determined from the low-field magnetoresistance saturates below 1 K, the amplitude of Aharonov-Bohm h/e oscillations increases strongly on a magnetic field scale proportional to the temperature. This provides strong evidence that a likely explanation for the frequently observed saturation of tau(phi) at low temperature in weakly disordered metallic thin films is the presence of extremely dilute magnetic impurities.
Hatano, T; Kubo, T; Tokura, Y; Amaha, S; Teraoka, S; Tarucha, S
2011-02-18
Aharonov-Bohm (AB) oscillations are studied for a parallel-coupled vertical double quantum dot with a common source and drain electrode. We observe AB oscillations of current via a one-electron bonding state as the ground state and an antibonding state as the excited state. As the center gate voltage becomes more negative, the oscillation period is clearly halved for both the bonding and antibonding states, and the phase changes by half a period for the antibonding state. This result can be explained by a calculation that takes account of the indirect interdot coupling via the two electrodes.
Recovery of the Aharonov-Bohm oscillations in asymmetrical quantum rings
NASA Astrophysics Data System (ADS)
Voskoboynikov, O.
2016-07-01
We theoretically investigate suppression and recovery of the Aharonov-Bohm oscillations of the diamagnetic response of electrons (holes) confined in self-assembled IncGa1-cAs/GaAs semiconductor reflection asymmetrical quantum rings. Based on the mapping method and gauge-origin-independent definition for the magnetic vector potential we simulate the energies and wave functions of the electron (hole) under external magnetic and electric fields. We examine the transformation of the ground state wave function of the electron (hole) in reflection asymmetrical rings from localized in one of the potential valleys (dotlike shape of the wave function) to distributed over all volume of the ring (ringlike shape) under an appropriate lateral electric field. This transformation greatly recovers the electron (hole) diamagnetic coefficient and Aharonov-Bohm oscillations of the diamagnetic response of the ring. However, the recovering electric field for the first Aharonov-Bohm diamagnetic oscillation of the electron is a suppressing one for the hole (and vice versa). This can block the recovery of the optical Aharonow-Bohm effect in IncGa1-cAs/GaAs asymmetrically wobbled rings. However, the recovery of the Aharonov-Bohm oscillations for the independent electron (hole) by the external electric field remains interesting and feasible objective for the asymmetric rings.
Aharonov-Bohm oscillations in (311)A GaAs 2D holes
NASA Astrophysics Data System (ADS)
Yau, Jeng-Bang; de Poortere, E. P.; Shayegan, M.
2001-03-01
We report the observation of Aharonov-Bohm (A-B) oscillations in high mobility (311)A GaAs two-dimensional (2D) holes. The 2D holes in GaAs have been demonstrated to exhibit a significant spin-orbit induced spin-splitting which can be tuned by changing the front/back gate voltages.(Papadakis et al.), Science 283, 2056 (1999). In addition to the A-B phase, a spin wave function acquires a geometrical phase, the Berry's phase,(M. V. Berry, Proc. R. Soc. Lond. A 392, 45 (1984).) when it travels adiabatically in a magnetic field. A-B rings made of this 2D material are therefore good candidates for the measurement of Berry's phase as proposed by Aronov et al..(A. G. Aronov et al.), Phys. Rev. Lett. 70, 343 (1993). We defined the A-B ring with a 2000 Åwide channel by electron beam lithography and deposited Ti/Au as the front gate. At T ~= 30 mK, we observe A-B oscillations with periods matching the geometry of the ring, providing evidence for the phase-coherent transport of 2D holes. By changing the front gate voltage, we observe changes in the magnitude and period of the oscillations. Furthermore, the Fourier spectra of some of the traces reveal a splitting of the peak, which may be a manifestation of the Berry's phase.
Beating of Aharonov-Bohm oscillations in a closed-loop interferometer
Jo, Sanghyun; Chang, Dong-In; Lee, Hu-Jong; Khym, Gyong Luck; Kang, Kicheon; Chung, Yunchul; Mahalu, Diana; Umansky, Vladimir
2007-07-15
One of the points at issue with closed-loop-type interferometers is beating in the Aharonov-Bohm (AB) oscillations. Recent observations suggest the possibility that the beating results from the Berry-phase pickup by the conducting electrons in materials with the strong spin-orbit interaction (SOI). In this study, we also observed beats in the AB oscillations in a gate-defined closed-loop interferometer fabricated on a GaAs/Al{sub 0.3}Ga{sub 0.7}As two-dimensional electron-gas heterostructure. Since this heterostructure has very small SOI, the picture of the Berry-phase pickup is ruled out. The observation of beats in this study, with the controllability of forming a single transverse subband mode in both arms of our gate-defined interferometer, also rules out the often-claimed multiple transverse subband effect. It is observed that nodes of the beats with an h/2e period exhibit a parabolic distribution for varying the side gate. These results are shown to be well interpreted, without resorting to the SOI effect, by the existence of two-dimensional multiple longitudinal modes in a single transverse subband. The Fourier spectrum of measured conductance, despite showing multiple h/e peaks with the magnetic-field dependence that are very similar to that from strong-SOI materials, can also be interpreted as the two-dimensional multiple-longitudinal-modes effect.
Aharonov-Bohm oscillations caused by non-topological surface states in Dirac nanowires
NASA Astrophysics Data System (ADS)
Enaldiev, V. V.; Volkov, V. A.
2016-12-01
One intriguing fingerprint of surface states in topological insulators is the Aharonov-Bohm effect in magnetoconductivity of nanowires. We show that surface states in nanowires of Dirac materials (bismuth, bismuth antimony, and lead tin chalcogenides) being in non-topological phase, exhibit the same effect as amendment to magnetoconductivity of the bulk states. We consider a simple model of a cylindrical nanowire, which is described by the 3D Dirac equation with a general T-invariant boundary condition. The boundary condition is determined by a single phenomenological parameter whose sign defines topological-like and non-topological surface states. The non-topological surface states emerge outside the gap. In a longitudinal magnetic field B, they lead to Aharonov-Bohm amendment for the density of states and correspondingly for the conductivity of the nanowire. The phase of these magnetic oscillations increases with B from π to 2π.
Quantum interference and Aharonov-Bohm oscillations in topological insulators
NASA Astrophysics Data System (ADS)
Bardarson, Jens H.; Moore, Joel E.
2013-05-01
Topological insulators (TIs) have an insulating bulk but a metallic surface. In the simplest case, the surface electronic structure of a three-dimensional (3D) TI is described by a single two-dimensional (2D) Dirac cone. A single 2D Dirac fermion cannot be realized in an isolated 2D system with time-reversal symmetry, but rather owes its existence to the topological properties of the 3D bulk wavefunctions. The transport properties of such a surface state are of considerable current interest; they have some similarities with graphene, which also realizes Dirac fermions, but have several unique features in their response to magnetic fields. In this review we give an overview of some of the main quantum transport properties of TI surfaces. We focus on the efforts to use quantum interference phenomena, such as weak anti-localization and the Aharonov-Bohm effect, to verify in a transport experiment the Dirac nature of the surface state and its defining properties. In addition to explaining the basic ideas and predictions of the theory, we provide a survey of recent experimental work.
Quantum interference and Aharonov-Bohm oscillations in topological insulators.
Bardarson, Jens H; Moore, Joel E
2013-05-01
Topological insulators (TIs) have an insulating bulk but a metallic surface. In the simplest case, the surface electronic structure of a three-dimensional (3D) TI is described by a single two-dimensional (2D) Dirac cone. A single 2D Dirac fermion cannot be realized in an isolated 2D system with time-reversal symmetry, but rather owes its existence to the topological properties of the 3D bulk wavefunctions. The transport properties of such a surface state are of considerable current interest; they have some similarities with graphene, which also realizes Dirac fermions, but have several unique features in their response to magnetic fields. In this review we give an overview of some of the main quantum transport properties of TI surfaces. We focus on the efforts to use quantum interference phenomena, such as weak anti-localization and the Aharonov-Bohm effect, to verify in a transport experiment the Dirac nature of the surface state and its defining properties. In addition to explaining the basic ideas and predictions of the theory, we provide a survey of recent experimental work.
NASA Astrophysics Data System (ADS)
Roy, Bidisha; Ji, Haojie; Dhomkar, Siddharth; Cadieu, Fred J.; Peng, Le; Moug, Richard; Tamargo, Maria C.; Kuskovsky, Igor L.
2013-02-01
A spectral analysis of the Aharonov-Bohm (AB) oscillations in photoluminescence intensity was performed for stacked type-II ZnTe/ZnSe quantum dots (QDs) fabricated within multilayered Zn-Se-Te system with sub-monolayer insertions of Te. Robust AB oscillations allowed for fine probing of distinguishable QDs stacks within the ensemble of QDs. The AB transition magnetic field, B AB , changed from the lower energy side to the higher energy side of the PL spectra revealing the presence of different sets of QDs stacks. The change occurs within the spectral range, where the contributing green and blue bands of the spectra overlapped. "Bundling" in lifetime measurements is seen at transition spectral regions confirming the results.
Jones-Smith, Katherine; Mathur, Harsh; Vachaspati, Tanmay
2010-02-15
A solenoid oscillating in vacuum will pair produce charged particles due to the Aharonov-Bohm (AB) interaction. We calculate the radiation pattern and power emitted for charged scalar particles. We extend the solenoid analysis to cosmic strings and find enhanced radiation from cusps and kinks on loops. We argue by analogy with the electromagnetic AB interaction that cosmic strings should emit photons due to the gravitational AB interaction of fields in the conical spacetime of a cosmic string. We calculate the emission from a kink and find that it is of similar order as emission from a cusp, but kinks are vastly more numerous than cusps and may provide a more interesting observational signature.
Kim, Hee Dae; Okuyama, Rin; Kyhm, Kwangseuk; Eto, Mikio; Taylor, Robert A; Nicolet, Aurelien L; Potemski, Marek; Nogues, Gilles; Dang, Le Si; Je, Ku-Chul; Kim, Jongsu; Kyhm, Ji-Hoon; Yoen, Kyu Hyoek; Lee, Eun Hye; Kim, Jun Young; Han, Il Ki; Choi, Wonjun; Song, Jindong
2016-01-13
The Aharonov-Bohm effect in ring structures in the presence of electronic correlation and disorder is an open issue. We report novel oscillations of a strongly correlated exciton pair, similar to a Wigner molecule, in a single nanoquantum ring, where the emission energy changes abruptly at the transition magnetic field with a fractional oscillation period compared to that of the exciton, a so-called fractional optical Aharonov-Bohm oscillation. We have also observed modulated optical Aharonov-Bohm oscillations of an electron-hole pair and an anticrossing of the photoluminescence spectrum at the transition magnetic field, which are associated with disorder effects such as localization, built-in electric field, and impurities.
Joshi, Sandeep K.; Sahoo, Debendranath; Jayannavar, A. M.
2001-08-15
We present a detailed analysis of Aharonov-Bohm (AB) interference oscillations manifested through transmission of an electron in a mesoscopic ring with a magnetic impurity atom inserted in one of its arms. Spin-polarized transport is also studied. The electron interacts with the impurity through exchange interaction, leading to spin-flip scattering. Transmission in the spin-flipped and -unflipped channels are explicitly calculated. We show that entanglement between electron and spin-flipper states leads to reduction of AB oscillations in spite of the absence of any inelastic scattering. The spin conductance (related to spin-polarized transmission coefficient) is asymmetric under flux reversal, as opposed to the two-probe conductance, which is symmetric. We point out certain limitations of this model in regard to the general notion of dephasing in quantum mechanics.
Li, Jin-Liang; Li, Yu-Xian
2008-11-19
Using nonequilibrium Green's function techniques, we investigate Andreev reflection and Aharonov-Bohm oscillations through a parallel-coupled double quantum dot connected with a ferromagnetic lead and a superconductor lead. The possibility of controlling Andreev reflection and Aharonov-Bohm oscillations of the system is explored by tuning the interdot coupling, the gate voltage, the magnetic flux, and the intradot spin-flip scattering. When the spin-flip scattering increases, Fano resonant peaks resulting from the asymmetrical levels of the two quantum dots begin to split, and Aharonov-Bohm oscillations are suppressed. Due to the interdot coupling, one strongly and one weakly coupled state of the system can be formed. The magnetic flux can exchange the function of the two states, which leads to a swap effect.
NASA Astrophysics Data System (ADS)
Barseghyan, M. G.; Manaselyan, A. Kh.; Laroze, D.; Kirakosyan, A. A.
2016-07-01
In this work we study the electronic states in quantum dot-ring complex nanostructures with an on-center hydrogenic impurity. The influence of the impurity on Aharonov-Bohm energy spectra oscillations and intraband optical absorption is investigated. It is shown that in the presence of a hydrogenic donor impurity the Aharonov-Bohm oscillations in quantum dot-ring structures become highly tunable. Furthermore, the presence of the impurity drastically changes the intraband absorption spectra due to the strong controllability of the electron localization type.
Aharonov-Bohm oscillations in a quasi-ballistic three-dimensional topological insulator nanowire
NASA Astrophysics Data System (ADS)
Cho, Sungjae; Dellabetta, Brian; Zhong, Ruidan; Schneeloch, John; Liu, Tiansheng; Gu, Genda; Gilbert, Matthew J.; Mason, Nadya
2015-07-01
Aharonov-Bohm oscillations effectively demonstrate coherent, ballistic transport in mesoscopic rings and tubes. In three-dimensional topological insulator nanowires, they can be used to not only characterize surface states but also to test predictions of unique topological behaviour. Here we report measurements of Aharonov-Bohm oscillations in (Bi1.33Sb0.67)Se3 that demonstrate salient features of topological nanowires. By fabricating quasi-ballistic three-dimensional topological insulator nanowire devices that are gate-tunable through the Dirac point, we are able to observe alternations of conductance maxima and minima with gate voltage. Near the Dirac point, we observe conductance minima for zero magnetic flux through the nanowire and corresponding maxima (having magnitudes of almost a conductance quantum) at magnetic flux equal to half a flux quantum; this is consistent with the presence of a low-energy topological mode. The observation of this mode is a necessary step towards utilizing topological properties at the nanoscale in post-CMOS applications.
Aharonov-Bohm oscillations in a quasi-ballistic three-dimensional topological insulator nanowire.
Cho, Sungjae; Dellabetta, Brian; Zhong, Ruidan; Schneeloch, John; Liu, Tiansheng; Gu, Genda; Gilbert, Matthew J; Mason, Nadya
2015-07-09
Aharonov-Bohm oscillations effectively demonstrate coherent, ballistic transport in mesoscopic rings and tubes. In three-dimensional topological insulator nanowires, they can be used to not only characterize surface states but also to test predictions of unique topological behaviour. Here we report measurements of Aharonov-Bohm oscillations in (Bi1.33Sb0.67)Se3 that demonstrate salient features of topological nanowires. By fabricating quasi-ballistic three-dimensional topological insulator nanowire devices that are gate-tunable through the Dirac point, we are able to observe alternations of conductance maxima and minima with gate voltage. Near the Dirac point, we observe conductance minima for zero magnetic flux through the nanowire and corresponding maxima (having magnitudes of almost a conductance quantum) at magnetic flux equal to half a flux quantum; this is consistent with the presence of a low-energy topological mode. The observation of this mode is a necessary step towards utilizing topological properties at the nanoscale in post-CMOS applications.
On a generalized Aharonov-Bohm plus oscillator system
NASA Astrophysics Data System (ADS)
Kibler, M.; Campigotto, C.
1993-09-01
Dynamical algebras, of the so(3,2) and so(3) types, are obtained for a generalized Aharanov-Bohm plus oscillator (ABO) system. Two types of coherent states are introduced for this generalized ABO system. A ( q,p)-analogue of this system is proposed that reduces to the generalized ABO system in the limiting case p= q-1=1. Finally, the classical motions for the generalized ABO system are briefly described.
Extracting fractional statistics from superperiodic Aharonov-Bohm oscillations
NASA Astrophysics Data System (ADS)
Kim, Eun-Ah; Kivelson, Steven
2006-03-01
We consider a quantum Hall interferometer in which the quasiparticles of a fractional quantum Hall (FQH) liquid with filling factor ν1=1/3 propagate around a large ring of radius r1, which is encircles an island with a smaller radius r2 occupied by FQH liquid with filling factor ν2=2/5. We study the conductance oscillations that result from the incompressibility of the FQH liquid occupying the island and the constructive interference condition for the quasiparticles encircling the outer ring. Since the constructive interference condition depends on both the magnetic flux enclosed by the encircling path and the statistical phase gained by the encircling quasiparticle due to the presence of quasiparticles in the island, such conductance oscillations can be used to detect signatures of fractional statistics. We find that oscillatory period depends on both radii, r1 and r2. We discuss the relation between our results and the recent experiments by F.E.Camino, W. Zhou and V.J. Goldman in the context of our model.
Aharonov-Bohm oscillations in Dirac semimetal Cd3As2 nanowires
NASA Astrophysics Data System (ADS)
Wang, Li-Xian; Li, Cai-Zhen; Yu, Da-Peng; Liao, Zhi-Min
2016-02-01
Three-dimensional Dirac semimetals, three-dimensional analogues of graphene, are unusual quantum materials with massless Dirac fermions, which can be further converted to Weyl fermions by breaking time reversal or inversion symmetry. Topological surface states with Fermi arcs are predicted on the surface and have been observed by angle-resolved photoemission spectroscopy experiments. Although the exotic transport properties of the bulk Dirac cones have been demonstrated, it is still a challenge to reveal the surface states via transport measurements due to the highly conductive bulk states. Here, we show Aharonov-Bohm oscillations in individual single-crystal Cd3As2 nanowires with low carrier concentration and large surface-to-volume ratio, providing transport evidence of the surface state in three-dimensional Dirac semimetals. Moreover, the quantum transport can be modulated by tuning the Fermi level using a gate voltage, enabling a deeper understanding of the rich physics residing in Dirac semimetals.
Aharonov-Bohm oscillations in Dirac semimetal Cd3As2 nanowires.
Wang, Li-Xian; Li, Cai-Zhen; Yu, Da-Peng; Liao, Zhi-Min
2016-02-23
Three-dimensional Dirac semimetals, three-dimensional analogues of graphene, are unusual quantum materials with massless Dirac fermions, which can be further converted to Weyl fermions by breaking time reversal or inversion symmetry. Topological surface states with Fermi arcs are predicted on the surface and have been observed by angle-resolved photoemission spectroscopy experiments. Although the exotic transport properties of the bulk Dirac cones have been demonstrated, it is still a challenge to reveal the surface states via transport measurements due to the highly conductive bulk states. Here, we show Aharonov-Bohm oscillations in individual single-crystal Cd3As2 nanowires with low carrier concentration and large surface-to-volume ratio, providing transport evidence of the surface state in three-dimensional Dirac semimetals. Moreover, the quantum transport can be modulated by tuning the Fermi level using a gate voltage, enabling a deeper understanding of the rich physics residing in Dirac semimetals.
Magneto-optical properties in inhomogeneous quantum dot: The Aharonov-Bohm oscillations effect
NASA Astrophysics Data System (ADS)
Nasri, Djillali; Bettahar, N.
2016-11-01
In this study, we investigated theoretically the effect of a magnetic field B on the linear, nonlinear, and total absorption coefficients (ACs) and the refractive index changes (RICs) associated with intersubband transitions in the HgS quantum shell. In the calculations, a diagonalization method was employed within the effective-mass approximation. We find that a three kinds of optical transitions (S-P, P-D and D-F) between the ground state and the first excited state appear, resulting from the oscillation of the ground state with B (Aharonov-Bohm effect). In the other hand, the magnetic field enhances and diminishes their related RICs and ACs intensities respectively for the three kinds of optical transitions, and shifts their peaks towards low energy (blue shift).
Aharonov-Bohm effect revisited
NASA Astrophysics Data System (ADS)
Eskin, Gregory
2015-04-01
Aharonov-Bohm effect is a quantum mechanical phenomenon that attracted the attention of many physicists and mathematicians since the publication of the seminal paper of Aharonov and Bohm [1] in 1959. We consider different types of Aharonov-Bohm effects such as the magnetic AB effect, electric AB effect, combined electromagnetic AB effect, AB effect for the Schrödinger equations with Yang-Mills potentials, and the gravitational analog of AB effect. We shall describe different approaches to prove the AB effect based on the inverse scattering problems, the inverse boundary value problems in the presence of obstacles, spectral asymptotics, and the direct proofs of the AB effect.
NASA Astrophysics Data System (ADS)
Chiao, Raymond Y.; Haun, Robert W.; Inan, Nader A.; Kang, Bong-Soo; Martinez, Luis A.; Minter, Stephen J.; Munoz, Gerardo A.; Singleton, Douglas A.
A thought experiment is proposed to demonstrate the existence of a gravitational, vector Aharonov-Bohm effect. We begin the analysis starting from four Maxwell-like equations for weak gravitational fields interacting with slowly moving matter. A connection is made between the gravitational, vector Aharonov-Bohm effect and the principle of local gauge invariance for nonrelativistic quantum matter interacting with weak gravitational fields. The compensating vector fields that are necessitated by this local gauge principle are shown to be incorporated by the DeWitt minimal coupling rule. The nonrelativistic Hamiltonian for weak, time-independent fields interacting with quantum matter is then extended to time-dependent fields, and applied to the problem of the interaction of radiation with macroscopically coherent quantum systems, including the problem of gravitational radiation interacting with superconductors. But first we examine the interaction of EM radiation with superconductors in a parametric oscillator consisting of a superconducting wire placed at the center of a high Q superconducting cavity driven by pump microwaves. Some room-temperature data will be presented demonstrating the splitting of a single microwave cavity resonance into a spectral doublet due to the insertion of a central wire. This would represent an unseparated kind of parametric oscillator, in which the signal and idler waves would occupy the same volume of space. We then propose a separated parametric oscillator experiment, in which the signal and idler waves are generated in two disjoint regions of space, which are separated from each other by means of an impermeable superconducting membrane. We find that the threshold for parametric oscillation for EM microwave generation is much lower for the separated configuration than the unseparated one, which then leads to an observable dynamical Casimir effect. We speculate that a separated parametric oscillator for generating coherent GR microwaves
Berry's phase manifestation in Aharonov-Bohm oscillations in single Bi nanowires
NASA Astrophysics Data System (ADS)
Gitsu, D. V.; Huber, T. E.; Konopko, L. A.; Nikolaeva, A. A.
2009-02-01
Here we report on Aharonov-Bohm oscillations of magnetoresistance (MR) of the single Bi nanowires with diameter d<80 nm. The samples were prepared by Ulitovsky technique and represented cylindrical single crystals with the 1011 orientation along the wire axis. Due to semimetal-to-semiconductor transformation and big density of surface states with strong spin-orbit interactions Bi nanowire should effectively become a conducting tube. The equidistant oscillations of the MR have been observed in a wide range of magnetic fields up to 14 T at various temperatures (1.5 K< T< 4.2 K) and angles θ (0< θ < 90°) of the sample orientation relative to the magnetic field. We have obtained longitudinal MR oscillations with periods ΔB1=Φ0/S and ΔB2=Φ0/2S, where Φ0=h/e is the flux quantum and S is the wire cross section. From B approx 8 T down to B=0 the extremums of Φ0/2S oscillations are shifted up to 3π at B=0 which is the manifestation of Berry phase shift due to carriers moving in inhomogeneous magnetic field. An interpretation of the MR oscillations in terms of a subband structure in the surface state band caused by quantum interference is presented.
Berman, G.P.; Bulgakov, E.N.; Campbell, D.K.; Krive, I.V.
1997-10-01
We consider Aharonov-Bohm oscillations in a mesoscopic semiconductor ring threaded by both a constant magnetic flux and a time-dependent, resonant magnetic field with one or two frequencies. Working in the ballistic regime, we establish that the theory of {open_quotes}quantum nonlinear resonance{close_quotes} applies, and thus that this system represents a possible solid-state realization of {open_quotes}quantum nonlinear resonance{close_quotes} and {open_quotes}quantum chaos.{close_quotes} In particular, we investigate the behavior of the time-averaged electron energy at zero temperature in the regimes of (i) an isolated quantum nonlinear resonance and (ii) the transition to quantum chaos, when two quantum nonlinear resonances overlap. The time-averaged energy exhibits sharp resonant behavior as a function of the applied constant magnetic flux, and has a staircase dependence on the amplitude of the external time-dependent field. In the chaotic regime, the resonant behavior exhibits complex structure as a function of flux and frequency. We compare and contrast the quantum chaos expected in these mesoscopic {open_quotes}solid-state atoms{close_quotes} with that observed in Rydberg atoms in microwave fields, and discuss the prospects for experimental observation of the effects we predict. {copyright} {ital 1997} {ital The American Physical Society}
NASA Technical Reports Server (NTRS)
Trammel, G. T.
1964-01-01
Aharonov-bohm paradox involving charge particle interaction with stationary current distribution showing that vector potential term in canonical momenta expression represents electromagnetic field momentum
Aharonov-Bohm oscillations caused by non-topological surface states in Dirac nanowires
NASA Astrophysics Data System (ADS)
Enaldiev, V. V.; Volkov, V. A.
2016-12-01
One intriguing fingerprint of surface states in topological insulators is the Aharonov-Bohm effect in magnetoconductivity of nanowires. We show that surface states in nanowires of Dirac materials (bismuth, bismuth antimony, and lead tin chalcogenides) being in non-topological phase, exhibit the same effect as amendment to magnetoconductivity of the bulk states. We consider a simple model of a cylindrical nanowire, which is described by the 3D Dirac equation with a general T -invariant boundary condition. The boundary condition is determined by a single phenomenological parameter whose sign defines topological-like and nontopological surface states. The non-topological surface states emerge outside the gap. In longitudinal magnetic field B they lead to Aharonov-Bohm amendment for the density of states and correspondingly for conductivity of the nanowire. The phase of these magnetooscillations increases with B from π to 2π.
Ren, S L; Heremans, J J; Gaspe, C K; Vijeyaragunathan, S; Mishima, T D; Santos, M B
2013-10-30
Low-temperature Aharonov-Bohm oscillations in the magnetoresistance of mesoscopic interferometric rings patterned on an InGaAs/InAlAs heterostructure are investigated for their dependence on excitation current and temperature. The rings have an average radius of 650 nm, and a lithographic arm width of 300 nm, yielding pronounced interference oscillations over a wide range of magnetic fields. Apart from a current and temperature dependence, the oscillation amplitude also shows a quasi-periodic modulation with applied magnetic field. The phase coherence length is extracted by analysis of the fundamental and higher Fourier components of the oscillations, and by direct analysis of the amplitude and its dependence on parameters. It is concluded that the Thouless energy forms the measure of excitation energies for quantum decoherence. The amplitude modulation finds an explanation in the effect of the magnetic flux threading the finite width of the interferometer arms.
NASA Astrophysics Data System (ADS)
Mtsuko, Davie; Aslan, Tahir; Ncube, Siphephile; Coleman, Christopher; Wamwangi, Daniel; Bhattacharyya, Somnath
2016-02-01
Magnetoresistance (MR) oscillations of multiple periodicities are recorded in singly connected silicon nanowires of diameter ≈50 \\text{nm} . At 100 K we observe oscillations of periodicity ≈1.78 \\text{T} and 0.444 T corresponding to h/e and h/4e Aharonov-Bohm (AB) oscillations, whereas at 10 K we record periodicities of 0.98 T, 0.49 T and 0.25 T corresponding to h/e, h/2e (Al'tshuler-Aronov-Spivak (AAS)) and h/4e oscillations. At 2.5 K we find magnetoresistance oscillations with multiple periodicities of 1.3 T, 0.52 T, and 0.325 T corresponding to AB and AAS oscillations. The h/2e and h/4e peaks can be attributed to the interference of time-reversed paths originating from the core orbits that scatter coherently on the surface of the nanowires multiple times. We also observed 20 mT and 60 mT oscillations of small amplitude superimposed on a quasi-periodic background which we attribute to the quantum interference of special surface states associated with skipping orbits that propagate quasi-ballistically. The aperiodic fluctuations in the MR at all temperatures are universal conductance fluctuations (UCF) originating from randomly spaced impurity scattering in the core of the nanowire.
Bogachek, E.N.; Landman, U.
1995-11-15
The thermodynamic and spectral properties of a two-dimensional electron gas with an antidot in a strong magnetic field, {ital r}{sub {ital c}}{le}{ital r}{sub 0}, where {ital r}{sub {ital c}} is the cyclotron radius and {ital r}{sub 0} is the antidot effective radius, are studied via a solvable model with the antidot confinement potential {ital U}{similar_to}1/{ital r}{sup 2}. The edge states localized at the antidot boundary result in an Aharonov-Bohm-type oscillatory dependence of the magnetization as a function of the magnetic field flux through the antidot. These oscillations are superimposed on the de Haas--van Alphen oscillations. In the strong-field limit, {h_bar}{omega}{sub {ital c}}{similar_to}{epsilon}{sub {ital F}}, where {omega}{sub {ital c}} is the cyclotron frequency and {epsilon}{sub {ital F}} is the Fermi energy, the amplitude of the Aharonov-Bohm-type oscillations of the magnetization due to the contribution of the lowest edge state is {similar_to}{mu}{sub {ital B}}{ital k}{sub {ital F}}{ital r}{sub {ital c}} ({mu}{sub {ital B}} is the Bohr magneton and {ital k}{sub {ital F}} is the Fermi wave vector). When the magnetic field is decreased, higher edge states can contribute to the magnetization, leading to the appearance of a beating pattern in the Aharonov-Bohm oscillations. The role of temperature in suppressing the oscillatory contribution due to higher edge states is analyzed. Rapid oscillations of the magnetization as a function of the Aharonov-Bohm flux, occurring on a scale of a small fraction of the flux quantum {ital hc}/{ital e}, are demonstrated. The appearance of a manifold of non- equidistant frequencies in the magneto-optical-absorption spectrum, due to transitions between electronic edge states localized near the antidot boundary, is predicted.
Magnetic-field-tuned Aharonov-Bohm oscillations and evidence for non-Abelian anyons at ν = 5/2.
Willett, R L; Nayak, C; Shtengel, K; Pfeiffer, L N; West, K W
2013-11-01
We show that the resistance of the ν = 5/2 quantum Hall state, confined to an interferometer, oscillates with the magnetic field consistent with an Ising-type non-Abelian state. In three quantum Hall interferometers of different sizes, resistance oscillations at ν = 7/3 and integer filling factors have the magnetic field period expected if the number of quasiparticles contained within the interferometer changes so as to keep the area and the total charge within the interferometer constant. Under these conditions, an Abelian state such as the (3, 3, 1) state would show oscillations with the same period as at an integer quantum Hall state. However, in an Ising-type non-Abelian state there would be a rapid oscillation associated with the "even-odd effect" and a slower one associated with the accumulated Abelian phase due to both the Aharonov-Bohm effect and the Abelian part of the quasiparticle braiding statistics. Our measurements at ν = 5/2 are consistent with the latter.
Oscillating dipole with fractional quantum source in Aharonov-Bohm electrodynamics
NASA Astrophysics Data System (ADS)
Modanese, Giovanni
We show, in the case of a special dipolar source, that electromagnetic fields in fractional quantum mechanics have an unexpected space dependence: propagating fields may have non-transverse components, and the distinction between near-field zone and wave zone is blurred. We employ an extension of Maxwell theory, Aharonov-Bohm electrodynamics, which is compatible with currents jν conserved globally but not locally; we have derived in another work the field equation ∂μFμν =jν +iν , where iν is a non-local function of jν , called "secondary current". Y. Wei has recently proved that the probability current in fractional quantum mechanics is in general not locally conserved. We compute this current for a Gaussian wave packet with fractional parameter a = 3 / 2 and find that in a suitable limit it can be approximated by our simplified dipolar source. Currents which are not locally conserved may be present also in other quantum systems whose wave functions satisfy non-local equations. The combined electromagnetic effects of such sources and their secondary currents are very interesting both theoretically and for potential applications.
Ferromagnetism's affect on the Aharonov-Bohm effect
NASA Astrophysics Data System (ADS)
Tatara, Gen; Barbara, Bernard
2001-11-01
Aharonov-Bohm (AB) and Altshuler-Aronov-Spivak (AAS) oscillation in a ferromagnetic ring is studied theoretically. Ferromagnetism does not affect the AB effect in an essential way, except that the magnetic field becomes a sum of the external and internal field. AAS oscillation would be suppressed for a minority spin channel in most 3d metals because of a strong s-d scattering, as indicated by a large spin dependence of a lifetime. The majority spin channel, in contrast, is expected to survive, due to a small density of states in the d band.
NASA Astrophysics Data System (ADS)
Sano, Kazuhiro; Ōno, Yoshiaki
2016-12-01
We investigate anomalous oscillations due to the Aharonov-Bohm (AB) and Aharonov-Casher (AC) effects of the one-dimensional Hubbard ring with flux in the strong coupling limit. By using the exact diagonalization method and the Shiba transformation, we examine the energies of the ground-state and a few excited states in the presence of the flux producing the AB or AC effect, where the transformation not only reverses the sign of the interaction U but also exchanges the role between the AB and AC effects in the model Hamiltonian. We systematically classify the AB and AC oscillations by using the number of minima Nmin of the ground-state energy as a function of a normalized phase shift ϕ for 0 ≤ ϕ < 1, and clarify the close relationship between the AB and AC effects. For example, it is shown that Nmin is given by NL - Ne (NL - N↑ + N↓) for the AB (AC) effect in the very strong attraction, where NL, Ne, N↑, and N↓ are the system size, the total number of electrons, the number of electrons with up-spin, and the number of electrons with down-spin, respectively, under the condition of NL > Ne > N↓ > N↑. In more special cases, such as for a half-filled band and the spin-balanced case (NL = Ne and N↓ = N↑), we find Nmin to be 0 (2) for the AB (AC) effect in the case of very strong repulsion. These results show us the nature of interesting phenomena originating from the interplay between the strong correlation and the quantum interference effect in a mesoscopic ring.
Inelastic transport through Aharonov-Bohm interferometer in Kondo regime
Yoshii, Ryosuke; Eto, Mikio; Sakano, Rui; Affleck, Ian
2013-12-04
We formulate elastic and inelastic parts of linear conductance through an Aharonov-Bohm (AB) ring with an embedded quantum dot in the Kondo regime. The inelastic part G{sub inel} is proportional to T{sup 2} when the temperature T is much smaller than the Kondo temperature T{sub K}, whereas it is negligibly small compared with elastic part G{sub el} when T ≫ T{sub K}. G{sub inel} weakly depends on the magnetic flux penetrating the AB ring, which disturbs the precise detection of G{sub el}/(G{sub el}+G{sub inel}) by the visibility of AB oscillation.
Aharonov-Bohm and Aharonov-Casher tunneling effects and edge states in double-barrier structures
Bogachek, E.N.; Landman, U. )
1994-07-15
The simultaneous occurrence of Aharonov-Bohm (AB) and Aharonov-Casher (AC) effects due to edge states in double-barrier two-dimensional wires formed by an electrostatic confinement potential, in the quantum Hall effect regime, is discussed. The AC effect is manifested via a shift of the AB conductance oscillations, and a method for measurement of the effect is proposed.
Aharonov-Bohm-type Effects in Triangular Antidot Lattice
NASA Astrophysics Data System (ADS)
Iye, Yaushiro; Ueki, Masaaki; Endo, Akira; Katsumoto, Shingo
2004-12-01
Three kinds of Aharonov-Bohm (AB)-type oscillation have been investigated in triangular antidot lattice fabricated from a GaAs/AlGaAs two-dimensional electron gas sample. The oscillation periods of Altshuler-Aronov-Spivak (AAS) effect and AB-type effect near zero magnetic field are determined by the unit cell area, whereas those of AB-type oscillations in the quantum Hall plateau transition regime are governed by the effective area of antidot. The evolution of the high-field AB-type oscillation as a function of gate voltage gives infomation on the profile of the self-consistent potential associated with compressible edge channels formed around antidot. The temperature dependences and decoherence mechanisms of the AAS and AB-type oscillations near zero magnetic field as well as the high-field AB-type oscillation are discussed.
On the Aharonov-Bohm effect with neutrons
Peshkin, M.
1994-11-01
The neutron interferometry phenomenon called scalar Aharonov-Bohm effect (SAB) follows from an ordinary local interaction, contrary to the usual Aharonov-Bohm effect with electrons (AB). I argue that SAB is not a topological effect by any useful definition. SAB in fact measures an apparently novel spin autocorrelation whose operator equations of motion contain the local torque in the magnetic field. The Aharonov-Casher effect shares these properties with SAB.
Magnetic edge states in Aharonov-Bohm graphene quantum rings
Farghadan, R. Heidari Semiromi, E.; Saffarzadeh, A.
2013-12-07
The effect of electron-electron interaction on the electronic structure of Aharonov-Bohm (AB) graphene quantum rings (GQRs) is explored theoretically using the single-band tight-binding Hamiltonian and the mean-field Hubbard model. The electronic states and magnetic properties of hexagonal, triangular, and circular GQRs with different sizes and zigzag edge terminations are studied. The results show that, although the AB oscillations in the all types of nanoring are affected by the interaction, the spin splitting in the AB oscillations strongly depends on the geometry and the size of graphene nanorings. We found that the total spin of hexagonal and circular rings is zero and therefore, no spin splitting can be observed in the AB oscillations. However, the non-zero magnetization of the triangular rings breaks the degeneracy between spin-up and spin-down electrons, which produces spin-polarized AB oscillations.
Aharonov-Bohm effect in monolayer phosphorene nanorings
NASA Astrophysics Data System (ADS)
Zhang, Rui; Wu, Zhenhua; Li, X. J.; Chang, Kai
2017-03-01
This work presents a theoretical demonstration of the Aharonov-Bohm (AB) effect in monolayer phosphorene nanorings (PNRs). Atomistic quantum transport simulations of PNRs are employed to investigate the impact of multiple modulation sources on the sample conductance. In the presence of a perpendicular magnetic field, we find that the conductance of both armchair and zigzag PNRs oscillate periodically in a low-energy window as a manifestation of the AB effect. Our numerical results reveal a giant magnetoresistance (MR) in zigzag PNRs (with a maximum magnitude approaching 2000%). It is attributed to the AB-effect-induced destructive interference phase over a wide energy range below the bottom of the second subband. We also demonstrate that PNR conductance is highly anisotropic, offering an additional way to modulate MR. The giant MR in PNRs is maintained at room temperature in the presence of the thermal broadening effect.
Size effects in Aharonov-Bohm graphene rings
NASA Astrophysics Data System (ADS)
Yan, Cong-Hua; Wei, Lian-Fu
2010-07-01
Aharonov-Bohm (AB) effects in mesoscopic metal rings have been extensively studied. In this paper, we investigate these effects on the persistent currents (PCs) in a closed graphene ring with broken time-reversal symmetry. A hard boundary condition is introduced to describe the Dirac electrons moving along such a ring-shaped configuration, and then the induced persistent currents are numerically calculated. Differing from the properties of PCs revealed in the metal AB rings, we show that the present PCs neither show the regular saw-tooth-like features nor present the odd-even symmetry of the electron number. More interestingly, we show that the energy difference between the two valleys and the amplitude of the oscillating PCs increase with the decrease (increase) of the radius (width) of the graphene ring. Our results imply that the AB effect and size-dependent PCs in ring-shaped microstructures could be tested at room temperature.
Size effects in Aharonov-Bohm graphene rings.
Yan, Cong-Hua; Wei, Lian-Fu
2010-07-28
Aharonov-Bohm (AB) effects in mesoscopic metal rings have been extensively studied. In this paper, we investigate these effects on the persistent currents (PCs) in a closed graphene ring with broken time-reversal symmetry. A hard boundary condition is introduced to describe the Dirac electrons moving along such a ring-shaped configuration, and then the induced persistent currents are numerically calculated. Differing from the properties of PCs revealed in the metal AB rings, we show that the present PCs neither show the regular saw-tooth-like features nor present the odd-even symmetry of the electron number. More interestingly, we show that the energy difference between the two valleys and the amplitude of the oscillating PCs increase with the decrease (increase) of the radius (width) of the graphene ring. Our results imply that the AB effect and size-dependent PCs in ring-shaped microstructures could be tested at room temperature.
Aharonov-Bohm radiation of fermions
Chu Yizen; Mathur, Harsh; Vachaspati, Tanmay
2010-09-15
We analyze Aharonov-Bohm radiation of charged fermions from oscillating solenoids and cosmic strings. We find that the angular pattern of the radiation has features that differ significantly from that for bosons. For example, fermionic radiation in the lowest harmonic is approximately isotropically distributed around an oscillating solenoid, whereas for bosons the radiation is dipolar. We also investigate the spin polarization of the emitted fermion-antifermion pair. Fermionic radiation from kinks and cusps on cosmic strings is shown to depend linearly on the ultraviolet cutoff, suggesting strong emission at an energy scale comparable to the string energy scale.
NASA Astrophysics Data System (ADS)
Kubo, T.; Tokura, Y.; Tarucha, S.
2010-01-01
We theoretically investigate spin-dependent electron transport through an Aharonov-Bohm-Casher interferometer containing a laterally coupled double quantum dot. In particular, we numerically calculate the Aharonov-Bohm and Aharonov-Casher oscillations of the linear conductance in the Kondo regime. We show that the AC oscillation in the Kondo regime deviates from the sinusoidal form.
Group-theoretical derivation of Aharonov-Bohm phase shifts
Hagen, C. R.
2013-02-15
The phase shifts of the Aharonov-Bohm effect are generally determined by means of the partial wave decomposition of the underlying Schroedinger equation. It is shown here that they readily emerge from an o(2,1) calculation of the energy levels employing an added harmonic oscillator potential which discretizes the spectrum.
The molecular Aharonov-Bohm effect redux
NASA Astrophysics Data System (ADS)
Zygelman, B.
2017-01-01
A solvable molecular collision model that predicts Aharonov-Bohm (AB) like scattering in the adiabatic approximation is introduced. For it, we propagate coupled channel wave packets without resorting to a Born-Oppenheimer (BO) approximation. In those, exact, solutions we find evidence of topological phase dislocation lines that are independent of the collision energy and provide definitive signatures of AB-like scattering. The results of these simulations contrast with the conclusions of a recent study that suggests survival of the molecular Aharonov-Bohm effect only in the adiabatic limit in which the nuclear reduced mass μ \\to ∞ . We discuss generalizations of this model and consider possible screening of the Mead-Truhlar vector potential by the presence of multiple conical intersections (CI). We demonstrate that the Wilson loop phase integral has the value -1 if it encloses an odd-number of CI's, and takes the value +1 for an even number. Within the scope of this model, we investigate the ultra-cold limit of scattering solutions in the presence of a conical intersection and comment on the relevance of Wigner threshold behavior for s-wave scattering.
Scattering on two Aharonov-Bohm vortices
NASA Astrophysics Data System (ADS)
Bogomolny, E.
2016-12-01
The problem of two Aharonov-Bohm (AB) vortices for the Helmholtz equation is examined in detail. It is demonstrated that the method proposed by Myers (1963 J. Math. Phys. 6 1839) for slit diffraction can be generalised to obtain an explicit solution for AB vortices. Due to the singular nature of AB interaction the Green function and scattering amplitude for two AB vortices obey a series of partial differential equations. Coefficients entering these equations, fulfil ordinary non-linear differential equations whose solutions can be obtained by solving the Painlevé III equation. The asymptotics of necessary functions for very large and very small vortex separations are calculated explicitly. Taken together, this means that the problem of two AB vortices is exactly solvable.
Coherent coupling of two quantum dots embedded in an Aharonov-Bohm interferometer.
Holleitner, A W; Decker, C R; Qin, H; Eberl, K; Blick, R H
2001-12-17
We define two laterally gated small quantum dots with less than 15 electrons in an Aharonov-Bohm geometry in which the coupling between the two dots can be changed. We measure Aharonov-Bohm oscillations for weakly coupled quantum dots. In an intermediate coupling regime we study molecular states of the double dot and extract the magnetic field dependence of the coherently coupled states.
Flux effect in superconducting hybrid Aharonov-Bohm rings
Stoof, T.H.; Nazarov, Y.V.
1996-07-01
We have extended the circuit theory of Andreev conductance [Phys. Rev. Lett. {bold 73}, 1420 (1994)] to diffusive superconducting hybrid structures that contain an Aharonov-Bohm ring. The electrostatic potential distribution in the system is predicted to be flux dependent with a period of the superconducting flux quantum {Phi}{sub 0}={ital h}/2{ital e}. When at least one tunnel barrier is present, the conductance of the system oscillates with the same period. {copyright} {ital 1996 The American Physical Society.}
Aharonov-Bohm effects in entangled molecules.
Kimball, J C; Frisch, H L
2004-08-27
Molecules which are magnetic and conducting, if suitably entangled (e.g., catenanes and knots) could exhibit Aharonov-Bohm effects which can be viewed as particular examples of a Berry phase. The corrections to the quantum energy levels reflect the entangled geometry of the molecules and, while small (they are proportional to the square of the fine structure constant), may be observable. We illustrate these corrections for a number of catenated and knotted structures. For couplings between the components of a catenane (link), the Aharonov-Bohm corrections are determined by integer-valued linking numbers. For knots, the Aharonov-Bohm correction is proportional to the geometric writhe of the knot.
Multiple-path Quantum Interference Effects in a Double-Aharonov-Bohm Interferometer.
Yang, Xf; Liu, Ys
2010-05-22
We investigate quantum interference effects in a double-Aharonov-Bohm (AB) interferometer consisting of five quantum dots sandwiched between two metallic electrodes in the case of symmetric dot-electrode couplings by the use of the Green's function equation of motion method. The analytical expression for the linear conductance at zero temperature is derived to interpret numerical results. A three-peak structure in the linear conductance spectrum may evolve into a double-peak structure, and two Fano dips (zero conductance points) may appear in the quantum system when the energy levels of quantum dots in arms are not aligned with one another. The AB oscillation for the magnetic flux threading the double-AB interferometer is also investigated in this paper. Our results show the period of AB oscillation can be converted from 2π to π by controlling the difference of the magnetic fluxes threading the two quantum rings.
Irregular Aharonov-Bohm effect for interacting electrons in a ZnO quantum ring.
Chakraborty, Tapash; Manaselyan, Aram; Barseghyan, Manuk
2017-02-22
The electronic states and optical transitions of a ZnO quantum ring containing few interacting electrons in an applied magnetic field are found to be very different from those in a conventional semiconductor system, such as a GaAs ring. The strong Zeeman interaction and the Coulomb interaction of the ZnO system, two important characteristics of the electron system in ZnO, exert a profound influence on the electron states and on the optical properties of the ring. In particular, our results indicate that the Aharonov-Bohm (AB) effect in a ZnO quantum ring strongly depends on the electron number. In fact, for two electrons in the ZnO ring, the AB oscillations become aperiodic, while for three electrons (interacting) the AB oscillations completely disappear. Therefore, unlike in conventional quantum ring topology, here the AB effect (and the resulting persistent current) can be controlled by varying the electron number.
Irregular Aharonov-Bohm effect for interacting electrons in a ZnO quantum ring
NASA Astrophysics Data System (ADS)
Chakraborty, Tapash; Manaselyan, Aram; Barseghyan, Manuk
2017-02-01
The electronic states and optical transitions of a ZnO quantum ring containing few interacting electrons in an applied magnetic field are found to be very different from those in a conventional semiconductor system, such as a GaAs ring. The strong Zeeman interaction and the Coulomb interaction of the ZnO system, two important characteristics of the electron system in ZnO, exert a profound influence on the electron states and on the optical properties of the ring. In particular, our results indicate that the Aharonov-Bohm (AB) effect in a ZnO quantum ring strongly depends on the electron number. In fact, for two electrons in the ZnO ring, the AB oscillations become aperiodic, while for three electrons (interacting) the AB oscillations completely disappear. Therefore, unlike in conventional quantum ring topology, here the AB effect (and the resulting persistent current) can be controlled by varying the electron number.
Macroscopic test of the Aharonov-Bohm effect.
Caprez, Adam; Barwick, Brett; Batelaan, Herman
2007-11-23
The Aharonov-Bohm (AB) effect is a purely quantum mechanical effect. The original (classified as type-I) AB-phase shift exists in experimental conditions where the electromagnetic fields and forces are zero. It is the absence of forces that makes the AB effect entirely quantum mechanical. Although the AB-phase shift has been demonstrated unambiguously, the absence of forces in type-I AB effects has never been shown. Here, we report the observation of the absence of time delays associated with forces of the magnitude needed to explain the AB-phase shift for a macroscopic system.
Macroscopic Test of the Aharonov-Bohm Effect
Caprez, Adam; Barwick, Brett; Batelaan, Herman
2007-11-23
The Aharonov-Bohm (AB) effect is a purely quantum mechanical effect. The original (classified as type-I) AB-phase shift exists in experimental conditions where the electromagnetic fields and forces are zero. It is the absence of forces that makes the AB effect entirely quantum mechanical. Although the AB-phase shift has been demonstrated unambiguously, the absence of forces in type-I AB effects has never been shown. Here, we report the observation of the absence of time delays associated with forces of the magnitude needed to explain the AB-phase shift for a macroscopic system.
Aharonov-Bohm excitons at elevated temperatures in type-II ZnTe/ZnSe quantum dots.
Sellers, I R; Whiteside, V R; Kuskovsky, I L; Govorov, A O; McCombe, B D
2008-04-04
Optical emission from type-II ZnTe/ZnSe quantum dots demonstrates large and persistent oscillations in both the peak energy and intensity indicating the formation of coherently rotating states. Furthermore, these Aharonov-Bohm oscillations are shown to be remarkably robust and persist until 180 K. This is at least one order of magnitude greater than the typical temperatures in lithographically defined rings. To our knowledge, this is the highest temperature at which the AB effect has been observed in solid-state and molecular nanostructures.
Mode Dependency of Quantum Decoherence Studied via an Aharonov-Bohm Interferometer.
Lo, Tung-Sheng; Lin, Yiping; Wu, Phillip M; Ling, Dah-Chin; Chi, C C; Chen, Jeng-Chung
2016-02-26
We investigate the dependence of decoherence on the mode number M in a multiple-mode Aharonov-Bohm (AB) interferometer. The design of the AB interferometer allows us to precisely determine M by the additivity rule of ballistic conductors; meanwhile, the decoherence rate is simultaneously deduced by the variance of the AB oscillation amplitude. The AB amplitude decreases and fluctuates with depopulating M. Moreover, the normalized amplitude exhibits a maximum at a specific M (∼9). Data analysis reveals that the charge-fluctuation-induced dephasing, which depends on the geometry and the charge relaxation resistance of the system, could play an essential role in the decoherence process. Our results suggest that the phase coherence, in principle, can be optimized using a deliberated design and pave one of the ways toward the engineering of quantum coherence.
Nguyen, V Hung; Niquet, Y-M; Dollfus, P
2014-05-21
We report on a numerical study of the Aharonov-Bohm (AB) effect and parity selective tunneling in pn junctions based on rectangular graphene rings where the contacts and ring arms are all made of zigzag nanoribbons. We find that when applying a magnetic field to the ring, the AB interference can reverse the parity symmetry of incoming waves and hence can strongly modulate the parity selective transmission through the system. Therefore, the transmission between two states of different parity exhibits the AB oscillations with a π-phase shift, compared to the case of states of the same parity. On this basis, it is shown that interesting effects, such as giant (both positive and negative) magnetoresistance and strong negative differential conductance, can be achieved in this structure. Our study thus presents a new property of the AB interference in graphene nanorings, which could be helpful for further understanding the transport properties of graphene mesoscopic systems.
Aharonov-Bohm effect without closing a loop
Retzker, A.; Nussinov, S.; Reznik, B.; Aharonov, Y.; Botero, A.
2006-03-15
We discuss the consequences of the Aharonov-Bohm (AB) effect in setups involving several charged particles, wherein none of the charged particles encloses a closed loop around the magnetic flux. We show that in such setups, the AB phase is encoded either in the relative phase of a bipartite or multipartite entangled photons states, or alternatively, gives rise to an overall AB phase that can be measured relative to another reference system. These setups involve processes of annihilation or creation of electron-hole pairs. We discuss the relevance of such effects in 'vacuum birefringence' in QED, and comment on their connection to other known effects.
Topology, Locality, and Aharonov-Bohm Effect with Neutrons
Peshkin, M.; Lipkin, H. J.
1995-04-10
Recent neutron interferometry experiments have been interpreted as demonstrating a new topological phenomenon similar in principle to the usual Aharonov-Bohm (AB) effect, but with the neutron's magnetic moment replacing the electron's charge. We show that he new phenomenon, called scalar AB (SAB) effect, follows from an ordinary local interaction, contrary to the usual AB effect, and we argue that the SAB effect is not a topological effect by any useful definition. We find that SAB actually measures an apparently novel spin autocorrelation whose operator equations of motion contain the local torque in the magnetic field. We note that the same remarks apply to the Aharonov-Casher effect.
Aharonov Bohm-type effects in different arrays of antidots
NASA Astrophysics Data System (ADS)
Kato, Masanori; Tanaka, Hiroyasu; Endo, Akira; Katsumoto, Shingo; Iye, Yasuhiro
2006-08-01
We have investigated Aharonov-Bohm-type oscillation in the quantum Hall plateau transition region in three types of square arrays of antidots; a large ( 50×160 antidots) array, a small ( 5×10 antidots) array, and the sample with antidots placed only near the side edges. The temperature dependence of the amplitude confirmed that the oscillation originates from the fine structure in the density of single particle states circumnavigating around each antidot. In addition, we have also observed Altshuler-Aronov-Spivak oscillation near zero magnetic field in square arrays of antidots.
Locality and topology in the molecular Aharonov-Bohm effect.
Sjöqvist, Erik
2002-11-18
It is shown that the molecular Aharonov-Bohm effect is neither nonlocal nor topological in the sense of the standard magnetic Aharonov-Bohm effect. It is further argued that there is a close relationship between the molecular Aharonov-Bohm effect and the Aharonov-Casher effect for an electrically neutral spin -1 / 2 particle encircling a line of charge.
Inelastic effects in Aharonov-Bohm molecular interferometers.
Hod, Oded; Baer, Roi; Rabani, Eran
2006-12-31
Inelastic effects arising from electron-phonon coupling in molecular Aharonov-Bohm (AB) interferometers are studied using the nonequilibrium Green's function method. Results for the magnetoconductance are compared for different values of the electron-phonon coupling strength. At low-bias voltages, the coupling to the phonons does not change the lifetime and leads mainly to scattering phase shifts of the conducting electrons. As a result of these dephasing processes, the magnetoconductance of the molecular AB interferometer becomes more sensitive to the threading magnetic flux as the electron-phonon coupling is increased, opposite to the behavior of an electric gate.
Thermoelectric effect in Aharonov-Bohm structures.
Lu, Xin; Wang, Jian-Sheng; Morrel, William G; Ni, Xiaoxi; Wu, Chang-Qin; Li, Baowen
2015-01-28
The thermoelectric effects of a single Aharonov-Bohm (SAB) ring and coupled double Aharonov-Bohm (DAB) rings have been investigated on a theoretical basis, taking into account the contributions of both electrons and phonons to the transport process by using the nonequilibrium Green's function technique. The thermoelectric figure of merit of the coupled DAB rings cannot be predicted directly by combining the values of two SAB ring systems due to the contribution of electron-phonon interaction to coupling between the two sites connecting the rings. We find that thermoelectric efficiency can be optimized by modulating the phases of the magnetic flux threading the two rings.
Aharonov-Bohm signature for neutral polarized excitons in type-II quantum dot ensembles.
Ribeiro, E; Govorov, A O; Carvalho, W; Medeiros-Ribeiro, G
2004-03-26
The Aharonov-Bohm effect is commonly believed to be a typical feature of the motion of a charged particle interacting with the electromagnetic vector potential. Here we present a magnetophotoluminescence study of type-II InP/GaAs self-assembled quantum dots, revealing the Aharonov-Bohm-type oscillations for neutral excitons when the hole ground state changes its angular momentum from l(h)=0 to l(h)=1, 2, and 3. The hole-ring parameters derived from a simple model are in excellent agreement with the structural parameters for this system.
Lorentz force effects for graphene Aharonov-Bohm interferometers
NASA Astrophysics Data System (ADS)
Mreńca-Kolasińska, A.; Szafran, B.
2016-11-01
We investigate magnetic deflection of currents that flow across the Aharonov-Bohm interferometers defined in graphene. We consider devices induced by closed n -p junctions in nanoribbons as well as etched quantum rings. The deflection effects on conductance are strictly correlated with the properties of the ring-localized quasibound states. The energy of these states, their lifetime, and the periodicity of the conductance oscillations are determined by orientation of the current circulating within the interferometer. The formation of high harmonics of conductance at high magnetic field and the role of intervalley scattering are discussed.
The Aharonov-Bohm effect in neutral liquids
NASA Astrophysics Data System (ADS)
Sonin, E. B.
2010-09-01
The Aharonov-Bohm effect was discovered as a quantum-mechanical effect for charged particles, but it has its counterpart in classical wave mechanics. The Aharonov-Bohm interference arises at the scattering of a sound wave by a vortex in classical and quantum hydrodynamics. This interference leads to a transverse force between quasiparticles and vortices in superfluids and superconductors. The Aharonov-Bohm effect was also generalized to neutral particles with magnetic or electric dipole momenta. The Aharonov-Bohm effect for charge particles and its modification for magnetic momenta (the Aharonov-Casher effect) have already been experimentally observed, and the efforts to detect the Aharonov-Bohm effect for electrically polarized neutral particles are on the way. A possible system for this detection is a Bose-condensate of excitons in a double quantum well. Observation of the Aharonov-Bohm effect in this system would provide direct evidence of Bose-Einstein condensation.
Tests of the Aharonov-Bohm effect
NASA Astrophysics Data System (ADS)
Caprez, Adam Preston
The Aharonov-Bohm effect was first proposed in 1959, and has stimulated discussion and controversy since the start. Seen by many as a purely quantum mechanical effect, it nevertheless involves such issues as gauge invariance and relativistic dynamics. This multi-faceted nature has led it to be considered a keystone of modern quantum theory. Over the past half-century, interest has remained strong in what many believe is still an open debate as to the purely quantum nature. Additionally, discovery of similar effects for particles other than electrons has further driven curiosity. To better understand the issues such as electromagnetic mass and relativistic effects involved in the Aharonov-Bohm effect, a theoretical study of a simpler two particle system was done. The goal was to understand the manner in which mass of the system behaved strictly classically as compared to a relativistically. As a result of this, a Gedanken experiment is presented which serves as a test for covariance. The two particle system was extended to a spherical shell interacting with a single particle, and a second thought experiment put forth to explore a coupling between electromagnetism and gravitation. In the course of searching for simpler systems which involved the same issues as the Aharonov-Bohm effect, a system presented in the Feynman Lectures of Physics was found to be appropriate. We conduct a complete relativistic analysis of this system as a step towards a full relativistic analysis of the Aharonov-Bohm effect. Given the history and significance of the Aharonov-Bohm effect, it is perhaps surprising that relevant experimental tests had not been completed. For the first time, we searched for time delays as an electron passes a macroscopic solenoid. Such time delays are characteristic of classical forces acting on the electron. No such delays were found, seemingly confirming the standard viewpoint. It is still possible a classical explanation may exist for microscopic solenoids
Three Quantum Dots Embedded in Aharonov-Bohm Rings
NASA Astrophysics Data System (ADS)
Toonen, Ryan; Hãttel, Andreas; Goswami, Srijit; Eberl, Karl; Eriksson, Mark; van der Weide, Daniel; Blick, Robert
2004-03-01
Coherent coupling of two quantum dots embedded in a ring-geometry has been demonstrated by Holleitner et al.(A.W. Holleitner, H. Qin, C.R. Decker, K. Eberl, and R.H. Blick, phCoherent Coupling of Two Quantum Dots Embedded in an Aharonov-Bohm Ring), Phys. Rev. Lett. 87, 256802 (2001) Recording of the Aharonov-Bohm oscillations in such a circuit has proven that the phases of electron wave functions can be manipulated directly. We have since enhanced the complexity of this system by embedding three quantum dots in such a ring-geometry. As before, our quantum dots are formed by laterally constricting a two-dimensional electron gas (2DEG) in an Al_xGa_1-xAs/GaAs heterostructure. The new, essential ingredient of this experiment is an additional third port--added to the ring for individually addressing the third quantum dot. This circuit allows us to investigate phenomena associated with phase-switching between separate ports. We will discuss first results and give a simple model of circuit operation.
High-temperature Aharonov-Bohm-Casher interferometer
NASA Astrophysics Data System (ADS)
Shmakov, P. M.; Dmitriev, A. P.; Kachorovskii, V. Yu.
2012-02-01
We study theoretically the combined effect of the spin-orbit and Zeeman interactions on the tunneling electron transport through a single-channel quantum ring threaded by magnetic flux. We focus on the high-temperature case (temperature is much higher than the level spacing in the ring) and demonstrate that spin-interference effects are not suppressed by thermal averaging. In the absence of the Zeeman coupling, the high-temperature tunneling conductance of the ring exhibits two types of oscillations: Aharonov-Bohm oscillations with magnetic flux and Aharonov-Casher oscillations with the strength of the spin-orbit interaction. For weak tunneling coupling, both oscillations have the form of sharp periodic antiresonances. In the vicinity of the antiresonances, the tunneling electrons acquire spin polarization, so that the ring serves as a spin polarizer. We also demonstrate that the Zeeman coupling leads to appearance of two additional peaks, both in the tunneling conductance and in the spin polarization.
Noncommutative analogue Aharonov-Bohm effect and superresonance
NASA Astrophysics Data System (ADS)
Anacleto, M. A.; Brito, F. A.; Passos, E.
2013-06-01
We consider the idea of modeling a rotating acoustic black hole by an idealized draining bathtub vortex which is a planar circulating flow phenomenon with a sink at the origin. We find the acoustic metric for this phenomenon from a noncommutative Abelian Higgs model. As such the acoustic metric not only describes a rotating acoustic black hole but also inherits the noncommutative characteristic of the spacetime. We address the issues of superresonance and analogue Aharonov-Bohm (AB) effect in this background. We mainly show that the scattering of planar waves by a draining bathtub vortex leads to a modified AB effect and due to spacetime noncommutativity, the phase shift persists even in the limit where the parameters associated with the circulation and draining vanish. Finally, we also find that the analogue AB effect and superresonance are competing phenomena at a noncommutative spacetime.
Relativistic currents on ideal Aharonov-Bohm cylinders
NASA Astrophysics Data System (ADS)
Cotăescu, Ion I.; Băltăţeanu, Doru-Marcel S.; Cotăescu, Ion I.
2016-06-01
The relativistic theory of the Dirac fermions moving on cylinders in external Aharonov-Bohm (AB) field is built starting with a suitably restricted Dirac equation whose spin degrees of freedom are not affected. The exact solutions of this equation on finite or infinite AB cylinders allow one to derive the relativistic circular and longitudinal currents pointing out their principal features. It is shown that all the circular currents are related to the energy in the same manner on cylinders or rings either in the relativistic approach or in the nonrelativistic one. The specific relativistic effect is the saturation of the circular currents for high values of the total angular momentum. Based on this property some approximative closed formulas are deduced for the total persistent current at T = 0 on finite AB cylinders. Moreover, it is shown that all the persistent currents on finite cylinders or rings have similar nonrelativistic limits.
Topology, locality, and Aharonov-Bohm effect with neutrons
Peshkin, M.; Lipkin, H.J. |
1995-04-10
Recent neutron interferometry experiments have been interpreted as demonstrating a new topological phenomenon similar in principle to the usual Aharonov-Bohm (AB) effect, but with the neutron`s magnetic moment replacing the electron`s charge. We show that the new phenomenon, called scalar AB (SAB) effect, follows from an ordinary local interaction, contrary to the usual AB effect, and we argue that the SAB effect is not a topological effect by any useful definition. We find that SAB actually measures an apparently novel spin autocorrelation whose operator equations of motion contain the local torque in the magnetic field. We note that the same remarks apply to the Aharonov-Casher effect.
Aharonov-Bohm-type quantum interference effects in narrow gap semiconductor heterostructures
NASA Astrophysics Data System (ADS)
Lillianfeld, R. B.; Kallaher, R. L.; Heremans, J. J.; Chen, Hong; Goel, N.; Chung, S. J.; Santos, M. B.; van Roy, W.; Borghs, G.
2009-03-01
We present experiments on quantum interference phenomena in semiconductors with strong spin-orbit interaction, using mesoscopic parallel ring arrays fabricated on InSb/InAlSb and InAs/AlGaSb heterostructures. Both external electric field effects and temperature dependence of the ring magnetoresistance are examined. Top-gate voltage-dependent oscillations in ring resistance in the absence of an external magnetic field are suggestive of Aharonov-Casher interference. At low magnetic fields the ring magnetoresistance is dominated by oscillations with h/2e periodicity characteristic of Altshuler-Aronov-Spivak (AAS) oscillations, whereas the h/e periodicity characteristic of Aharonov-Bohm (AB) oscillations persists to high magnetic fields. Fourier spectra (FS) reveal AB amplitudes on the same order as AAS amplitudes at low fields, and in some samples reveal a splitting of the AB peaks, which has been interpreted as a signature of Berry's phase. The FS are also used to quantify the temperature dependence of the oscillation amplitudes (NSF DMR-0618235, DOE DE-FG02-08ER46532, NSF DMR-0520550).
The electric Aharonov-Bohm effect
Weder, Ricardo
2011-05-15
The seminal paper of Aharonov and Bohm [Phys. Rev. 115, 485 (1959)] is at the origin of a very extensive literature in some of the more fundamental issues in physics. They claimed that electromagnetic fields can act at a distance on charged particles even if they are identically zero in the region of space where the particles propagate, that the fundamental electromagnetic quantities in quantum physics are not only the electromagnetic fields but also the circulations of the electromagnetic potentials; what gives them a real physical significance. They proposed two experiments to verify their theoretical conclusions. The magnetic Aharonov-Bohm effect, where an electron is influenced by a magnetic field that is zero in the region of space accessible to the electron, and the electric Aharonov-Bohm effect where an electron is affected by a time-dependent electric potential that is constant in the region where the electron is propagating, i.e., such that the electric field vanishes along its trajectory. The Aharonov-Bohm effects imply such a strong departure from the physical intuition coming from classical physics that it is no wonder that they remain a highly controversial issue after more than fifty years, in spite of the fact that they are discussed in most of the text books in quantum mechanics. The magnetic case has been studied extensively. The experimental issues were settled by the remarkable experiments of Tonomura et al. [Phys. Rev. Lett. 48, 1443 (1982); Phys. Rev. Lett. 56, 792 (1986)] with toroidal magnets, that gave a strong evidence of the existence of the effect, and by the recent experiment of Caprez et al. [Phys. Rev. Lett. 99, 210401 (2007)] that shows that the results of the Tonomura et al. experiments cannot be explained by the action of a force. The theoretical issues were settled by Ballesteros and Weder [Commun. Math. Phys. 285, 345 (2009); J. Math. Phys. 50, 122108 (2009); Commun. Math. Phys. 303, 175 (2011)] who rigorously proved that quantum
Cooper, Benjamin K; Yakovenko, Victor M
2006-01-27
Different types of angular magnetoresistance oscillations in quasi-one-dimensional layered materials, such as organic conductors (TMTSF)2X, are explained in terms of Aharonov-Bohm interference in interlayer electron tunneling. A two-parameter pattern of oscillations for generic orientations of a magnetic field is visualized and compared to the experimental data. Connections with angular magnetoresistance oscillations in other layered materials are discussed.
Photonic Aharonov-Bohm effect based on dynamic modulation.
Fang, Kejie; Yu, Zongfu; Fan, Shanhui
2012-04-13
We show that when the refractive index of a photonic system is harmonically modulated, the phase of the modulation introduces an effective gauge potential for photons. This effective gauge potential can be used to create a photonic Aharonov-Bohm effect. We show that the photonic Aharonov-Bohm effect provides the optimal mechanism for achieving complete on-chip nonmagnetic optical isolation.
Photonic Aharonov-Bohm effect in photon-phonon interactions.
Li, Enbang; Eggleton, Benjamin J; Fang, Kejie; Fan, Shanhui
2014-01-01
The Aharonov-Bohm effect is one of the most intriguing phenomena in both classical and quantum physics, and associates with a number of important and fundamental issues in quantum mechanics. The Aharonov-Bohm effects of charged particles have been experimentally demonstrated and found applications in various fields. Recently, attention has also focused on the Aharonov-Bohm effect for neutral particles, such as photons. Here we propose to utilize the photon-phonon interactions to demonstrate that photonic Aharonov-Bohm effects do exist for photons. By introducing nonreciprocal phases for photons, we observe experimentally a gauge potential for photons in the visible range based on the photon-phonon interactions in acousto-optic crystals, and demonstrate the photonic Aharonov-Bohm effect. The results presented here point to new possibilities to control and manipulate photons by designing an effective gauge potential.
A charged particle in a homogeneous magnetic field accelerated by a time-periodic Aharonov-Bohm flux
Kalvoda, T.; Stovicek, P.
2011-10-15
We consider a nonrelativistic quantum charged particle moving on a plane under the influence of a uniform magnetic field and driven by a periodically time-dependent Aharonov-Bohm flux. We observe an acceleration effect in the case when the Aharonov-Bohm flux depends on time as a sinusoidal function whose frequency is in resonance with the cyclotron frequency. In particular, the energy of the particle increases linearly for large times. An explicit formula for the acceleration rate is derived with the aid of the quantum averaging method, and then it is checked against a numerical solution and a very good agreement is found. - Highlights: > A nonrelativistic quantum charged particle on a plane. > A homogeneous magnetic field and a periodically time-dependent Aharonov-Bohm flux. > The quantum averaging method applied to a time-dependent system. > A resonance of the AB flux with the cyclotron frequency. > An acceleration with linearly increasing energy; a formula for the acceleration rate.
Flux-free conductance modulation in a helical Aharonov--Bohm interferometer.
Taira, Hisao; Shima, Hiroyuki
2010-06-23
A novel conductance oscillation in a twisted quantum ring composed of a helical atomic configuration is theoretically predicted. The internal torsion of the ring is found to cause a quantum phase shift in the wavefunction that describes the electron's motion along the ring. The resulting conductance oscillation is free from magnetic flux penetrating inside the ring, which is in complete contrast with the case for the ordinary Aharonov-Bohm effect observed in untwisted quantum rings.
Two-particle Aharonov-Bohm effect and entanglement in the electronic Hanbury Brown-Twiss setup.
Samuelsson, P; Sukhorukov, E V; Büttiker, M
2004-01-16
We analyze a Hanbury Brown-Twiss geometry in which particles are injected from two independent sources into a mesoscopic conductor in the quantum Hall regime. All partial waves end in different reservoirs without generating any single-particle interference; in particular, there is no single-particle Aharonov-Bohm effect. However, exchange effects lead to two-particle Aharonov-Bohm oscillations in the zero-frequency current cross correlations. We demonstrate that this is related to two-particle orbital entanglement, detected via violation of a Bell inequality. The transport is along edge states and only adiabatic quantum point contacts and normal reservoirs are employed.
Resonance and phase shift in an open Aharonov-Bohm ring with an embedded quantum dot.
Hedin, Eric R; Joe, Yong S; Satanin, Arkady M
2009-01-07
The transmission and phase properties of electron transport through a quantum dot (QD) with variable coupling to a third-terminal probe are investigated analytically for the case of the QD connected directly to source and drain reservoirs and when the QD is embedded in one arm of an Aharonov-Bohm (AB) ring. Using the tight-binding model, explicit analytical expressions of the transmission through the QD for each case are given. Expressions for the conductance with coupling to the third terminal, which breaks unitarity and phase-locking, are also given. It is shown that in a three-terminal interferometer the zero of the Fano resonance in the transmission moves off the real energy axis for finite values of the coupling parameter. The zero orbits around the pole in the complex energy plane as a function of magnetic flux through the ring, and can be returned to the real energy axis unless the coupling parameter exceeds a critical value. With the QD embedded in one arm of the AB ring, the electron transmission and the transmission phase, and the phase of the AB oscillations, are described in relation to the degree of coupling to the third-terminal probe which opens the interferometer. By tuning the degree of coupling to the probe, it is shown that the phase of the AB oscillations can be made to match the intrinsic phase of the QD, facilitating experimental characterization of the phase response of the QD.
Optical detection of the Aharonov-Bohm effect on a charged particle in a nanoscale quantum ring.
Bayer, M; Korkusinski, M; Hawrylak, P; Gutbrod, T; Michel, M; Forchel, A
2003-05-09
We study spectroscopically the current produced by a charged particle moving in a nanosize semiconductor quantum ring subject to a perpendicular magnetic field. Several Aharonov-Bohm oscillations are observed in the emission of a charged exciton confined in a single ring structure. The magnetic field period of the oscillations correlates well with the size of the rings.
Time-dependent Pauli equation in the presence of the Aharonov-Bohm effect
Bouguerra, Y.; Bounames, A.; Maamache, M.; Saadi, Y.
2008-04-15
We use the Lewis-Riesenfeld theory to determine the exact form of the wavefunctions of a two-dimensional Pauli equation of a charged spin 1/2 particle with time-dependent mass and frequency in the presence of the Aharonov-Bohm effect and a two-dimensional time-dependent harmonic oscillator. We find that the irregular solution at the origin as well as the regular one contributes to the phase of the wavefunction.
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.
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.
Locality of the Aharonov-Bohm-Casher effect
NASA Astrophysics Data System (ADS)
Kang, Kicheon
2015-05-01
We address the question of locality versus nonlocality in the Aharonov-Bohm and the Aharonov-Casher effects. For this purpose, we investigate all possible configurations of ideal shielding of the overlap between the electromagnetic fields generated by a charge and by a magnetic flux and analyze their consequences on the Aharonov-Bohm-Casher interference. In a classical treatment of shielding, the Aharonov-Bohm-Casher effect vanishes regardless of the geometry of shielding when the local overlap of electromagnetic fields is completely eliminated. On the other hand, the result depends on the configuration of shielding if the charge quantization in the superconducting shield is taken into account. It is shown that our results are fully understood in terms of the fluctuating local-field interaction. Our analysis strongly supports the alternative view on the Aharonov-Bohm-Casher interference that the effects originate from the local action of electromagnetic fields.
Calculation of the Aharonov-Bohm wave function
Alvarez, M.
1996-08-01
A calculation of the Aharonov-Bohm wave function is presented. The result is an asymptotic series of confluent hypergeometric functions which is finite at the forward direction. {copyright} {ital 1996 The American Physical Society.}
Aharonov-Casher and scalar Aharonov-Bohm topological effects.
Dulat, Sayipjamal; Ma, Kai
2012-02-17
We reexamine the topological and nonlocal natures of the Aharonov-Casher and scalar Aharonov-Bohm phase effects. The underlying U(1) gauge structure is exhibited explicitly. And the conditions for developing topological Aharonov-Casher and scalar Aharonov-Bohm phases are clarified. We analyze the arguments of M. Peshkin and H. J. Lipkin [Phys. Rev. Lett. 74, 2847 (1995)] in detail and show that they are based on the wrong Hamiltonian which yields their conclusion incorrect.
Quantum Faraday effect in a double-dot Aharonov-Bohm loop
NASA Astrophysics Data System (ADS)
Kang, Kicheon
2012-07-01
We investigate the role of Faraday's law of induction manifested in the quantum state of Aharonov-Bohm (AB) loops. In particular, a flux-switching experiment is proposed for a double-dot AB loop to verify the phase shift induced by Faraday's law. The induced Faraday phase is shown to be geometric and nontopological. This study demonstrates that the relation between the local phases of a ring at different fluxes is not arbitrary but is instead determined by Faraday's inductive law, which is in contrast to the arbitrary local phase of an AB loop for a given flux.
Lai, Wenxi; Xing, Yunhui; Ma, Zhongshui
2013-05-22
Phase relaxation of electrons transferring through an electromechanical transistor is studied using the Aharonov-Bohm interferometer. Using the quantum master equation approach, the phase properties of an electron are numerically analyzed based on the interference fringes. The coherence of the electron is partially destroyed by its scattering on excited levels of the local nanomechanical oscillator. The transmission amplitudes with respect to two adjacent mechanical vibrational levels have a phase difference of π. The character of the π phase shift depends on the oscillator frequency only and is robust over a wide range of values of the applied voltage, tunneling length and damping rate of the mechanical oscillator.
Aharonov-Bohm interference in topological insulator nanoribbons.
Peng, Hailin; Lai, Keji; Kong, Desheng; Meister, Stefan; Chen, Yulin; Qi, Xiao-Liang; Zhang, Shou-Cheng; Shen, Zhi-Xun; Cui, Yi
2010-03-01
Topological insulators represent unusual phases of quantum matter with an insulating bulk gap and gapless edges or surface states. The two-dimensional topological insulator phase was predicted in HgTe quantum wells and confirmed by transport measurements. Recently, Bi(2)Se(3) and related materials have been proposed as three-dimensional topological insulators with a single Dirac cone on the surface, protected by time-reversal symmetry. The topological surface states have been observed by angle-resolved photoemission spectroscopy experiments. However, few transport measurements in this context have been reported, presumably owing to the predominance of bulk carriers from crystal defects or thermal excitations. Here we show unambiguous transport evidence of topological surface states through periodic quantum interference effects in layered single-crystalline Bi(2)Se(3) nanoribbons, which have larger surface-to-volume ratios than bulk materials and can therefore manifest surface effects. Pronounced Aharonov-Bohm oscillations in the magnetoresistance clearly demonstrate the coherent propagation of two-dimensional electrons around the perimeter of the nanoribbon surface, as expected from the topological nature of the surface states. The dominance of the primary h/e oscillation, where h is Planck's constant and e is the electron charge, and its temperature dependence demonstrate the robustness of these states. Our results suggest that topological insulator nanoribbons afford promising materials for future spintronic devices at room temperature.
Observation of "partial coherence" in an Aharonov-Bohm interferometer with a quantum dot.
Aikawa, Hisashi; Kobayashi, Kensuke; Sano, Akira; Katsumoto, Shingo; Iye, Yasuhiro
2004-04-30
We report experiments on the interference through spin states of electrons in a quantum dot (QD) embedded in an Aharonov-Bohm (AB) interferometer. We have picked up a spin-pair state, for which the environmental conditions are ideally similar. The AB amplitude is traced in a range of gate voltage that covers the pair. The behavior of the asymmetry in the amplitude around the two Coulomb peaks agrees with the theoretical prediction that the spin-flip process in a QD is related to the quantum dephasing of electrons. These results constitute evidence of "partial coherence" due to an entanglement of spins in the QD and in the interferometer.
Chen, Xi; Zheng, Qing-Rong; Su, Gang
2010-05-12
The spin transfer effect in a ferromagnet-quantum dot (insulator)-ferromagnet Aharonov-Bohm (AB) ring system with Rashba spin-orbit (SO) interactions is investigated by means of the Keldysh nonequilibrium Green function method. It is found that both the magnitude and direction of the spin transfer torque (STT) acting on the right ferromagnet electrode can be effectively controlled by changing the magnetic flux threading the AB ring or the gate voltage on the quantum dot. The STT can be greatly augmented by matching a proper magnetic flux and an SO interaction at a cost of low electrical current. The STT, electrical current and spin current are uncovered to oscillate with the magnetic flux. The present results are expected to be useful for information storage in nanospintronics.
Global analogue of the Aharonov-Bohm effect
Navin, R.L.
1993-12-31
This thesis deals with a global analogue of the Aharonov-Bohm effect previously pointed out by other authors. The effect was not well understood because the pure Aharonov-Bohm cross section was thought to be merely an approximate low energy limit. This thesis provides a detailed analysis and reveals that in the particular model considered, there is an exact Aharonov-Bohm cross section over the energy range that a mass splitting occurs. At energies slightly above the mass splitting, the effect has completely disappeared and there is effectively no scattering at large distances. This is a curious observation as it was previously thought that a global theory would not act exactly like a local one over an extended range of energies. It begs the heretical speculation that experimentally observed forces modelled with Lagrangians possessing local symmetries may have an underlying global theory.
Transient electric current through an Aharonov-Bohm ring after switching of a two-level system
NASA Astrophysics Data System (ADS)
Tatara, Gen
2002-05-01
The response of the electronic current through an Aharonov-Bohm ring after a two-level-system is switched on is calculated perturbatively by use of a nonequilibrium Green function. In the ballistic case the amplitude of the Aharonov-Bohm oscillation is shown to decay to a new equilibrium value due to scattering into other electronic states. The relaxation of the Altshuler-Aronov-Spivak oscillation in the diffusive case, due to the dephasing effect, is also calculated. The time scale of the relaxation is determined by characteristic relaxation times of the system and the splitting of a two-level-system. The oscillation phase is not affected. Experimental studies of current response would give us direct information about characteristic times of mesoscopic systems.
Aharonov-Casher and Scalar Aharonov-Bohm Topological Effects
NASA Astrophysics Data System (ADS)
Dulat, Sayipjamal; Ma, Kai
2012-02-01
We reexamine the topological and nonlocal natures of the Aharonov-Casher and scalar Aharonov-Bohm phase effects. The underlying U(1) gauge structure is exhibited explicitly. And the conditions for developing topological Aharonov-Casher and scalar Aharonov-Bohm phases are clarified. We analyze the arguments of M. Peshkin and H. J. Lipkin [Phys. Rev. Lett. 74, 2847 (1995)PRLTAO0031-900710.1103/PhysRevLett.74.2847] in detail and show that they are based on the wrong Hamiltonian which yields their conclusion incorrect.
Aharonov-Bohm superperiod in a Laughlin quasiparticle interferometer.
Camino, F E; Zhou, Wei; Goldman, V J
2005-12-09
We report an Aharonov-Bohm superperiod of five magnetic flux quanta (5h/e) observed in a Laughlin quasiparticle interferometer, where an edge channel of the 1/3 fractional quantum Hall fluid encircles an island of the 2/5 fluid. This result does not violate the gauge invariance argument of the Byers-Yang theorem because the magnetic flux, in addition to affecting the Aharonov-Bohm phase of the encircling 1/3 quasiparticles, creates the 2/5 quasiparticles in the island. The superperiod is accordingly understood as imposed by the anyonic statistical interaction of Laughlin quasiparticles.
Experimental test for approximately dispersionless forces in the Aharonov-Bohm effect
NASA Astrophysics Data System (ADS)
Becker, Maria; Batelaan, Herman
2016-07-01
A new class of forces, approximately dispersionless forces, were recently predicted as part of a semiclassical description of the Aharonov-Bohm effect. Electron time-of-flight measurements have been performed that test for such forces. Magnetized iron cores used in the previous time-of-flight experiment may affect potential back-action forces and have, therefore, been eliminated. We report that no forces were detected. This finding supports the local and nonlocal, quantum descriptions of the AB effect and rules out local, semiclassical descriptions.
Absence of the Electric Aharonov-Bohm Effect due to Induced Charges.
Wang, Rui-Feng
2015-09-22
This paper states that the induced charge should not be neglected in the electric Aharonov-Bohm (A-B) effect. If the induced charge is taken into account, the interference pattern of the moving charge will not change with the potential difference between the two metal tubes. It means that the scalar potential itself can not affect the phase of the moving charge, and the true factor affecting the phase of the moving charge is the energy of the system including the moving charge and the induced charge.
Absence of the Electric Aharonov-Bohm Effect due to Induced Charges
Wang, Rui-Feng
2015-01-01
This paper states that the induced charge should not be neglected in the electric Aharonov-Bohm (A-B) effect. If the induced charge is taken into account, the interference pattern of the moving charge will not change with the potential difference between the two metal tubes. It means that the scalar potential itself can not affect the phase of the moving charge, and the true factor affecting the phase of the moving charge is the energy of the system including the moving charge and the induced charge. PMID:26392302
Feynman's Relativistic Electrodynamics Paradox and the Aharonov-Bohm Effect
NASA Astrophysics Data System (ADS)
Caprez, Adam; Batelaan, Herman
2009-03-01
An analysis is done of a relativistic paradox posed in the Feynman Lectures of Physics involving two interacting charges. The physical system presented is compared with similar systems that also lead to relativistic paradoxes. The momentum conservation problem for these systems is presented. The relation between the presented analysis and the ongoing debates on momentum conservation in the Aharonov-Bohm problem is discussed.
Aharonov-Bohm interactions of a vector unparticle
NASA Astrophysics Data System (ADS)
Kobakhidze, Archil
2007-11-01
Recently Georgi argued that a hypothetical conformally invariant hidden sector weakly interacting with ordinary particles will have unusual manifestations at low energies in terms of effective degrees of freedom called unparticles. In this paper we consider Aharonov-Bohm type of interactions due to the vector unparticle coupled to elementary fermions. We have found that the quantum mechanical phase shift is path dependent.
Excitonic Aharonov-Bohm effect in a two-dimensional quantum ring
Gonzalez-Santander, C.; Dominguez-Adame, F.; Roemer, R. A.
2011-12-15
We study theoretically the optical properties of an exciton in a two-dimensional ring threaded by a magnetic flux. We model the quantum ring by a confining potential that can be continuously tuned from strictly one-dimensional to truly two-dimensional with finite radius-to-width ratio. We present an analytic solution of the problem when the electron-hole interaction is short ranged. The oscillatory dependence of the oscillator strength as a function of the magnetic flux is attributed to the Aharonov-Bohm effect. The amplitude of the oscillations changes upon increasing the width of the quantum ring. We find that the Aharonov-Bohm oscillations of the ground state of the exciton decrease with increasing the width, but, remarkably, the amplitude remains finite down to radius-to-width ratios less than unity. We attribute this resilience of the excitonic oscillations to the nonsimple connectedness of our chosen confinement potential with its centrifugal core at the origin.
Electron Interferometry in the Quantum Hall Regime: Aharonov-Bohm Effect of Interacting Electrons
Lin, P.V.; Camino, F.; Goldman, V.J.
2009-09-01
An apparent h/fe Aharonov-Bohm flux period, where f is an integer, has been reported in coherent quantum Hall devices. Such subperiod is not expected for noninteracting electrons and thus is thought to result from interelectron Coulomb interaction. Here we report experiments in a Fabry-Perot interferometer comprised of two wide constrictions enclosing an electron island. By carefully tuning the constriction front gates, we find a regime where interference oscillations with period h/2e persist throughout the transition between the integer quantum Hall plateaus 2 and 3, including half-filling. In a large quantum Hall sample, a transition between integer plateaus occurs near half-filling, where the bulk of the sample becomes delocalized and thus dissipative bulk current flows between the counterpropagating edges ('backscattering'). In a quantum Hall constriction, where conductance is due to electron tunneling, a transition between forward and backscattering is expected near the half-filling. In our experiment, neither period nor amplitude of the oscillations show a discontinuity at half-filling, indicating that only one interference path exists throughout the transition. We also present experiments and an analysis of the front-gate dependence of the phase of the oscillations. The results point to a single physical mechanism of the observed conductance oscillations: Aharonov-Bohm interference of interacting electrons in quantum Hall regime.
Non-traditional Aharonov-Bohm effects in condensed matter
Krive, I.V. ); Rozhavsky, A.S. )
1992-05-10
In 1959, Aharonov and Bohm proposed an elegant experiment demonstrating observability of electromagnetic potentials (or, which is the same, the non-locality of the wave function of charged particles) in quantum mechanics. This paper discusses the Aharonov-Bohm effect, based on the fundamental principles of quantum theory, as the superposition principles, the quantum character of motion of particles and locality of the interaction of a charge with an electromagnetic potential L{sub int} = j{sub {mu}}A{sup {mu}}. It is thus no wonder that the Aharonov-Bohm's paper aroused much dispute which is still ongoing. Originally, the Aharonov-Bohm effect (ABE) means the dependence of the interference pattern on the magnetic fluid flux {phi} in a Gendaken experiment on a coherent electron beam in the field of an infinitely thin solenoid. Later, however, it became common to refer to the Aharonov-Bohm phenomenon wherever the characteristics of systems under study appear to depend on the flux {phi} in the absence of electric and magnetic fields. In this sense, it was highly interesting to analyze the ABE in condensed media (the many-particle Aharonov-Bohm effect), in particular to study the dependence of the thermodynamic and kinetic characteristics, e.g., of metal on the flux. Such a problem was first discussed by Byers and Yang who formulated the general theorems related to the ABE in conducting condensed media. The next important step was the work of Kulik who formulated a concrete model and calculated the flux-dependent contribution to the metal free energy and provided a first clear formulation of the requirements to reveal.
Further Considerations Regarding the Aharonov-Bohm Effect and the Wavefunction of the Entire System
NASA Astrophysics Data System (ADS)
Walstad, Allan
2016-12-01
In an earlier paper it was demonstrated that the hypothesized electrostatic version of the Aharonov-Bohm ("AB") effect does not exist. The conclusion follows straightforwardly once one recognizes that interference takes place in the configuration space of the entire system, including the experimental apparatus, and the wavefunction of the apparatus cannot be ignored. Two additional results are presented here. 1. Observations of interference that had been attributed to an analogue of the electrostatic AB effect (or "scalar effect") are actually due to a magnetic AB effect. 2. In the original magnetic AB effect itself, there is no phase shift if it is possible effectively to shield the solenoid from the influence of the passing electron. This result is not in conflict with the landmark experiments of Tonomura and colleagues if Wang's recent claim is correct, that superconductive shielding could not have isolated the toroidal magnet from the magnetic pulse of the passing electron.
Against a proposed alternative explanation of the Aharonov-Bohm effect.
Peshkin, M.; Physics
2010-09-03
The Aharonov-Bohm (AB) effect is understood to demonstrate that the Maxwell fields can act nonlocally in some situations. However it has been suggested from time to time that the AB effect is somehow a consequence of a local classical electromagnetic field phenomenon involving energy that is temporarily stored in the overlap between the external field and the field of which the beam particle is the source. That idea was shown in the past not to work for some models of the source of the external field. Here a more general proof is presented for the magnetic AB effect to show that the overlap energy is always compensated by another contribution to the energy of the magnetic field in such a way that the sum of the two is independent of the external flux. Therefore no such mechanism can underlie the AB effect.
NASA Astrophysics Data System (ADS)
Liu, Jian-Heng; Tu, Matisse Wei-Yuan; Zhang, Wei-Min
2016-07-01
By considering a nanoscale Aharonov-Bohm (AB) interferometer consisting of a laterally coupled double dot coupled to the source and drain electrodes, we investigate the AB phase dependence of the bonding and antibonding states and the transport currents via the bonding and antibonding state channels. The relations of the AB phase dependence between the quantum states and the associated transport current components are analyzed, which provides useful information for the reconstruction of quantum states through the measurement of the transport current in such systems. We also obtain the validity of the experimental analysis [given in T. Hatano et al., Phys. Rev. Lett. 106, 076801 (2011), 10.1103/PhysRevLett.106.076801] that bonding state currents in different energy configurations are almost the same. With the coherent properties in the quantum dot states as well as in the transport currents, we also provide a way to manipulate the bonding and antibonding states through the AB magnetic flux.
Further Considerations Regarding the Aharonov-Bohm Effect and the Wavefunction of the Entire System
NASA Astrophysics Data System (ADS)
Walstad, Allan
2017-03-01
In an earlier paper it was demonstrated that the hypothesized electrostatic version of the Aharonov-Bohm ("AB") effect does not exist. The conclusion follows straightforwardly once one recognizes that interference takes place in the configuration space of the entire system, including the experimental apparatus, and the wavefunction of the apparatus cannot be ignored. Two additional results are presented here. 1. Observations of interference that had been attributed to an analogue of the electrostatic AB effect (or "scalar effect") are actually due to a magnetic AB effect. 2. In the original magnetic AB effect itself, there is no phase shift if it is possible effectively to shield the solenoid from the influence of the passing electron. This result is not in conflict with the landmark experiments of Tonomura and colleagues if Wang's recent claim is correct, that superconductive shielding could not have isolated the toroidal magnet from the magnetic pulse of the passing electron.
Observation of Aharonov-Bohm effects by neutron interferometry
NASA Astrophysics Data System (ADS)
Werner, Samuel A.; Klein, Anthony G.
2010-09-01
The special and unique techniques of neutron interferometry have been used to observe a number of topological effects. These include the quantum mechanical phase shift of a neutron due to the Earth's rotation (the quantum analog of the Michelson-Gale-Pearson experiment with light), the phase shift of a particle carrying a magnetic moment (a neutron) encircling a line charge (the Aharonov-Casher effect) and the scalar Aharonov-Bohm effect, observed with a pulsed magnetic field solenoid and time-of-flight neutron detection. On the occasion of the 50th anniversary of the Aharonov-Bohm paper, we provide an overview of the neutron interferometry technique and a description of these three historic experiments.
Scalar Aharonov-Bohm effect with longitudinally polarized neutrons
Allman, B. E.; Lee, W.-T.; Motrunich, O. I.; Werner, S. A.
1999-12-01
In the scalar Aharonov-Bohm effect, a charged particle (electron) interacts with the scalar electrostatic potential U in the field-free (i.e., force-free) region inside an electrostatic cylinder (Faraday cage). Using a perfect single-crystal neutron interferometer we have performed a ''dual'' scalar Aharonov-Bohm experiment by subjecting polarized thermal neutrons to a pulsed magnetic field. The pulsed magnetic field was spatially uniform, precluding any force on the neutrons. Aligning the direction of the pulsed magnetic field to the neutron magnetic moment also rules out any classical torque acting to change the neutron polarization. The observed phase shift is purely quantum mechanical in origin. A detailed description of the experiment, performed at the University of Missouri Research Reactor, and its interpretation is given in this paper. (c) 1999 The American Physical Society.
Quantum oscillation and decoherence in triangular antidot lattice
NASA Astrophysics Data System (ADS)
Ueki, M.; Endo, A.; Katsumoto, S.; Iye, Y.
2004-04-01
Quantum oscillation phenomena in triangular antidot lattice have been investigated. Altshuler-Aronov-Spivak oscillations and Aharonov-Bohm (AB)-type oscillations are observed at low magnetic field, and AB-type oscillations due to edge channels are observed in the quantum Hall regime. Measurements of the temperature dependence of these oscillations furnish information on the mechanism of decoherence in the antidot lattice, which is compared with the single ring case.
Quantum anholonomies in time-dependent Aharonov-Bohm rings
Tanaka, Atushi; Cheon, Taksu
2010-08-15
Anholonomies in eigenstates are studied through time-dependent variations of a magnetic flux in an Aharonov-Bohm ring. The anholonomies in the eigenenergy and the expectation values of eigenstates are shown to persist beyond the adiabatic regime. The choice of the gauge of the magnetic flux is shown to be crucial to clarify the relationship of these anholonomies to the eigenspace anholonomy, which is described by a non-Abelian connection in the adiabatic limit.
Topological Aharonov-Bohm Effect and Pseudo-Particle Bundles
NASA Astrophysics Data System (ADS)
Payandeh, Farrin
2016-10-01
Exploiting a topological approach, we discuss the outstanding Aharonov-Bohm effect and try to explain it in the context of the principal P(M, U(1)) bundle. We show that this could be done by excluding a specific region from the main manifold which acts as the solenoid around which the effect is observed. Moreover, we discuss the impacts of pseudo-particles in this topological approach.
Nonlinear conductance in a ballistic Aharonov-Bohm ring.
Hernández, Alexis R; Lewenkopf, Caio H
2009-10-16
The nonlinear electronic transport properties of a ballistic Aharonov-Bohm ring are investigated. It is demonstrated how the electronic interaction breaks the phase rigidity in a two-probe mesoscopic device as the voltage bias is increased. The possibility of studying interference effects in the nonlinear regime is addressed. The occurrence of magnetic field symmetries in higher order conductance coefficients is analyzed. The results are compared with recent experimental data.
Levinson theorem for Aharonov-Bohm scattering in two dimensions
Sheka, Denis D.; Mertens, Franz G.
2006-11-15
We apply the recently generalized Levinson theorem for potentials with inverse-square singularities [Sheka et al., Phys. Rev. A 68, 012707 (2003)] to Aharonov-Bohm systems in two dimensions (2D). By this theorem, the number of bound states in a given mth partial wave is related to the phase shift and the magnetic flux. The results are applied to 2D soliton-magnon scattering.
Analytic Aharonov-Bohm rings — Currents readout from Zeeman spectrum
NASA Astrophysics Data System (ADS)
Xiao, Mufei; Reyes-Serrato, Armando
2016-06-01
This paper reports the work on the development and analysis of a model for quantum rings in which persistent currents are induced by Aharonov-Bohm (AB) or other similar effects. The model is based on a centric and annual potential profile. The time-independent Schrödinger equation including an external magnetic field and an AB flux is analytically solved. The outputs, namely energy dispersion and wavefunctions, are analyzed in detail. It is shown that the rotation quantum number m is limited to small numbers, especially in weak confinement, and a conceptual proposal is put forward for acquiring the flux and eventually estimating the persistent currents in a Zeeman spectroscopy. The wavefunctions and electron distributions are numerically studied and compared to one-dimensional (1D) quantum well. It is predicated that the model and its solutions, eigen energy structure and analytic wavefunctions, would be a powerful tool for studying various electric and optical properties of quantum rings.
Resonant Transmission of Electron Spin States through Multiple Aharonov-Bohm Rings
NASA Astrophysics Data System (ADS)
Cutright, Jim; Hedin, Eric; Joe, Yong
2011-10-01
An Aharonov-Bohm (AB) ring with embedded quantum dots (QD) in each arm and one -dimensional nanowires attached as leads acts as a primitive cell in this analysis. When a tunable, external magnetic field is parallel to the surface area of the ring it causes Zeeman splitting in the energy levels of the QDs. An electron that traverses these energy levels has the potential to interfere with other electrons and to produce spin polarized output. It is already known that upon output the transmission of the electrons through this system will have a resonant peak at each Zeeman split energy level. A system where multiple AB rings are connected in series is studied, to see how having the electrons pass through multiple, identical rings effects the resonant peaks in the transmission and the degree of spin polarization.
Absence of localization in a disordered one-dimensional ring threaded by an Aharonov-Bohm flux.
Heinrichs, Jean
2009-07-22
Absence of localization is demonstrated analytically to leading order in weak disorder in a one-dimensional Anderson model of a ring threaded by an Aharonov-Bohm (AB) flux. The result follows from adapting an earlier perturbation treatment of disorder in a superconducting ring subjected to an imaginary vector potential proportional to a depinning field for flux lines bound to random columnar defects parallel to the axis of the ring. The absence of localization in the ring threaded by an AB flux for sufficiently weak disorder is compatible with large free-electron-type persistent current obtained in recent studies of the above model.
Spin-dependent transport caused by the local magnetic moments inserted in the Aharonov-Bohm rings.
Shelykh, I A; Kulov, M A; Galkin, N G; Bagraev, N T
2007-06-20
We analyse the conductance of an Aharonov-Bohm (AB) ring with a quantum point contact (QPC) that is inserted in one of its arms and which contains a single electron. The conductance of the device is calculated as a function of the one-dimensional (1D) carrier concentration and the value of the magnetic field perpendicular to the plane of the AB ring. The exchange interaction between the electron localized inside QPC and freely propagating electrons is shown to modify the conductance pattern at small carrier concentration significantly, giving rise to the effects related to the formation of the '0.7 feature' in the quantum conductance staircase.
Peshkin, Murray
1996-03-25
The electrons in a conductor surrounding an external magnetic field are acted on by a vector potential that cannot be removed by a gauge transformation. Nevertheless, a macroscopic normal conductor can experience no Aharonov-Bohm (AB) effect. That is proved by assuming only that a normal conductor lacks off-diagonal long-range order (ODLRO), which means that the electrons lack long-range phase coherence. Then by restricting the Hilbert space to density matrices which lack ODLRO, one can introduce a restricted gauge transformation that removes the interaction of the conductor with the vector potential. Consequently, the AB effect on a beam particle is not shielded by the conductor.
Forward-smooth high-order uniform Aharonov-Bohm asymptotics
NASA Astrophysics Data System (ADS)
Berry, M. V.
2016-07-01
The Aharonov-Bohm (AB) function, describing a plane wave scattered by a flux line, is expanded asymptotically in a Fresnel-integral based series whose terms are smooth in the forward direction and uniformly valid in angle and flux. Successive approximations are valid for large distance r from the flux (or short wavelength) but are accurate even within one wavelength of it. Coefficients of all the terms are exhibited explicitly for the forward direction, enabling the high-order asymptotics to be understood in detail. The series is factorally divergent, with optimal truncation error exponentially small in r. Systematic resummation gives further exponential improvement. Terms of the series satisfy a resurgence relation: the high orders are related to the low orders. Discontinuities in the backward direction get smaller order by order, with systematic cancellation by successive terms. The relation to an earlier scheme based on the Cornu spiral is discussed.
Electron spin transport through an Aharonov Bohm ring—a spin switch
NASA Astrophysics Data System (ADS)
Jia, Cheng-Long; Wang, Shun-Jin; Luo, Hong-Gang; An, Jun-Hong
2004-03-01
Electron spin transport through an Aharonov-Bohm ring driven by time-dependent inhomogeneous magnetic fields is treated. The system possesses an su(2)l × su(2)s dynamical symmetry in both orbital angular momentum space and spin space, and is thus proved to be integrable according to algebraic dynamics. Based on the analytical solutions, the relevant physical quantities such as electric current, spin current, magnetization and conductance are calculated. It is found that for a magnetic field with pgr/2 twist angle, the direction of spin-polarization will be reversed at zero magnetic flux. In the resonant rotating magnetic field, the spin transmission is oscillating with time t, and can reach unity, so that a complete spin flip can also be induced. The results obtained may be of practical significance for the design of nano-electromagnetic spin devices, such as a spin switch, in a controllable way.
Electromagnetic Aharonov-Bohm effect in a two-dimensional electron gas ring
NASA Astrophysics Data System (ADS)
van der Wiel, W. G.; Nazarov, Yu. V.; de Franceschi, S.; Fujisawa, T.; Elzerman, J. M.; Huizeling, E. W.; Tarucha, S.; Kouwenhoven, L. P.
2003-01-01
We define a mesoscopic ring in a two-dimensional electron gas interrupted by two tunnel barriers, enabling us to apply a well-defined potential difference between the two halves of the ring. The electron interference in the ring is modified using a perpendicular magnetic field and a bias voltage. We observe clear Aharonov-Bohm oscillations up to the quantum Hall regime as a function of both parameters. The electron travel time between the barriers is found to increase with the applied magnetic field. Introducing a scattering model, we develop a method to measure the nonequilibrium electron dephasing time, which becomes very short at high voltages and magnetic fields. The relevance of electron-electron interactions is discussed.
Aharonov-Bohm effect as a probe of interaction between magnetic impurities.
Galitski, Victor M; Vavilov, Maxim G; Glazman, Leonid I
2005-03-11
We study the effects of the RKKY interaction between magnetic impurities on the mesoscopic conductance fluctuations of a metal ring with dilute magnetic impurities. At sufficiently low temperatures and strong magnetic fields, the loss of electron coherence occurs mainly due to the scattering off rare pairs of strongly coupled magnetic impurities. We establish a relation between the dephasing rate and the distribution function of the exchange interaction within such pairs. In the case of the RKKY exchange interaction, this rate exhibits 1/B(2) behavior in strong magnetic fields. We demonstrate that the Aharonov-Bohm conductance oscillations may be used as a probe of the distribution function of the exchange interaction between magnetic impurities in metals.
Electronic Aharonov-Bohm effect induced by quantum vibrations.
Shekhter, R I; Gorelik, L Y; Glazman, L I; Jonson, M
2006-10-13
Mechanical displacements of a nanoelectromechanical system shift the electron trajectories and hence perturb phase coherent charge transport through the device. We show theoretically that in the presence of a magnetic field such quantum-coherent displacements may give rise to an Aharonov-Bohm-type of effect. In particular, we demonstrate that quantum vibrations of a suspended carbon nanotube result in a positive nanotube magnetoresistance, which decreases slowly with the increase of temperature. This effect may enable one to detect quantum displacement fluctuations of a nanomechanical device.
Aharonov-Bohm conductance modulation in ballistic carbon nanotubes.
Lassagne, B; Cleuziou, J-P; Nanot, S; Escoffier, W; Avriller, R; Roche, S; Forró, L; Raquet, B; Broto, J-M
2007-04-27
We report on magnetoconductance experiments in ballistic multiwalled carbon nanotubes threaded by magnetic fields as large as 55 T. In the high temperature regime (100 K), giant modulations of the conductance, mediated by the Fermi level location, are unveiled. The experimental data are consistently analyzed in terms of the field-dependent density of states of the external shell that modulates the injection properties at the electrode-nanotube interface, and the resulting linear conductance. This is the first unambiguous experimental evidence of Aharonov-Bohm effect in clean multiwalled carbon nanotubes.
Hidden photons in Aharonov-Bohm-type experiments
NASA Astrophysics Data System (ADS)
Arias, Paola; Diaz, Christian; Diaz, Marco Aurelio; Jaeckel, Joerg; Koch, Benjamin; Redondo, Javier
2016-07-01
We discuss the Aharonov-Bohm effect in the presence of hidden photons kinetically mixed with the ordinary electromagnetic photons. The hidden photon field causes a slight phase shift in the observable interference pattern. It is then shown how the limited sensitivity of this experiment can be largely improved. The key observation is that the hidden photon field causes a leakage of the ordinary magnetic field into the supposedly field-free region. The direct measurement of this magnetic field can provide a sensitive experiment with a good discovery potential, particularly below the ˜meV mass range for hidden photons.
Spectroscopic detectability of the molecular Aharonov-Bohm effect.
Englman, R
2016-01-14
It is theoretically shown that the emission spectra from an excited Jahn-Teller state in which the ions undergo a forced periodic trajectory have an M-shaped form, directly due to the sign change by the Berry-phase factor. The presence of a weak spectral sideline is noted and the effects of a nonlinear vibronic coupling are calculated. Experimental verifications of the results, e.g., on R'-centers in LiF, are proposed. The dip in the M-shaped emission line is a novel, and perhaps unique, spectroscopic manifestation of the "molecular Aharonov-Bohm effect."
Perturbation theory and the Aharonov-Bohm effect
Hagen, C.R.
1995-08-15
The perturbation theory expansion of the Aharonov-Bohm scattering amplitude has previously been studied in the context of quantum mechanics for spin-0 and spin-1/2 particles as well as in Galilean covariant field theory. This problem is reconsidered in the framework of the model in which the flux line is considered to have a finite radius which is shrunk to zero at the end of the calculation. General agreement with earlier results is obtained but with the advantage of a treatment which unifies all the various subcases.
Relativistic persistent currents in ideal Aharonov-Bohm rings
NASA Astrophysics Data System (ADS)
Cotăescu, Ion I.; Băltăţeanu, Doru-Marcel; Cotăescu, Ion
2016-11-01
The exact solutions of the complete Dirac equation for fermions moving in ideal Aharonov-Bohm rings are used for deriving the exact expressions of the relativistic partial currents. It is shown that as in the nonrelativistic case, these currents can be related to the derivative of the fermion energy with respect to the flux parameter. A specific relativistic effect is the saturation of the partial currents for high values of the total angular momentum. Based on this property, the total relativistic persistent current at T = 0 is evaluated giving its analytical expression and showing how this depends on the ring parameters.
Conservation of momentum and the Aharonov-Bohm Effect
NASA Astrophysics Data System (ADS)
Caprez, Adam; Batelaan, Herman
2008-05-01
The Aharonov-Bohm Effect serves as an example of a purely quantum mechanical phenomenon in which classical forces on the electron are thought to vanish. The presence of forces is still an ongoing debate [1,2]. Surprisingly, a complete special relativistic treatment of the forces in the electron-solenoid system has never been done [3]. We present our ongoing theoretical work on the issue, and explore a connection between Feynman's well-known example [3] of two moving point charges and the Aharonov-Bohm Effect. The relation between this theoretical work and our earlier experimental results [4] is also discussed. [1] T.H. Boyer, J. Phys. A. 39, 3455 (2006). [2] G.C. Hegerfeldt and J.T. Neumann, [quant-ph] arXiv:0801.0799v1 (2008). [3] Y. Aharonov and D. Rohrlich, Quantum Paradoxes: Quantum Theory for the Perplexed (Wiley-VCH, Weinheim, 2005). [4] The Feynman Lectures on Physics. Vol. II, pp. 26-2-26-5 (1964). [5] A. Caprez, B. Barwick, and H. Batelaan. Phys. Rev. Lett. 99, 210401 (2007).
Relativistic Aharonov-Bohm effect in the presence of planar Coulomb potentials
Khalilov, V.R.
2005-01-01
Exact analytic solutions are found to the Dirac equation in 2+1 dimensions for a combination of an Aharonov-Bohm potential and the Lorentz three-vector and scalar Coulomb potentials. By means of the solutions obtained the relativistic quantum Aharonov-Bohm effect is studied for the free (in the presence of a Lorentz three-vector Coulomb potential) and bound fermion states. We obtain the total scattering amplitude in a combination of the Aharonov-Bohm and Lorentz three-vector Coulomb potentials as a sum of two scattering amplitudes. This modifies the expression for the standard Aharonov-Bohm cross section due to the interference of these two amplitudes with each other. We discuss that the observable quantities can be the phases of electron wave functions or the energies of bound states.
Longhi, Stefano
2014-10-15
We suggest a method for trapping photons in quasi-one-dimensional waveguide or coupled-resonator lattices, which is based on an optical analogue of the Aharonov-Bohm cages for charged particles. Light trapping results from a destructive interference of Aharonov-Bohm type induced by a synthetic magnetic field, which is realized by periodic modulation of the waveguide/resonator propagation constants/resonances.
What did we learn from the Aharonov-Bohm effect? Is spin 1/2 different?
Peshkin, M.
1994-06-01
I review what has been learned about fundamental issues in quantum mechanics from the Aharonov-Bohm effect. Following that, I consider the Aharonov-Casher effect and the Scalar Aharonov-Bohm effect, in both of which a spin-1/2 particle interacts with a local electromagnetic field through its magnetic moment, and conclude that those effects can be described as observable effects of local torques.
Aharonov-Bohm interferences from local deformations in graphene
NASA Astrophysics Data System (ADS)
de Juan, Fernando; Cortijo, Alberto; Vozmediano, María A. H.; Cano, Andrés
2011-10-01
One of the most interesting aspects of graphene is the close relation between its structural and electronic properties. The observation of ripples both in free-standing graphene and in samples on a substrate has given rise to active investigation of the membrane-like properties of graphene, and the origin of the ripples remains one of the most interesting open problems concerning this system. The interplay of structural and electronic properties is successfully described by the modelling of curvature and elastic deformations by fictitious gauge fields. These fields have become an experimental reality after the observation of the Landau levels that can form in graphene due to strain. Here we propose a device to detect microstresses in graphene based on a scanning-tunnelling-microscopy set-up able to measure Aharonov-Bohm interferences at the nanometre scale. The predicted interferences in the local density of states are created by the fictitious magnetic field associated with elastic deformations of the sample.
An Aharonov-Bohm interferometer for determining Bloch band topology.
Duca, L; Li, T; Reitter, M; Bloch, I; Schleier-Smith, M; Schneider, U
2015-01-16
The geometric structure of a single-particle energy band in a solid is fundamental for a wide range of many-body phenomena and is uniquely characterized by the distribution of Berry curvature over the Brillouin zone. We realize an atomic interferometer to measure Berry flux in momentum space, in analogy to an Aharonov-Bohm interferometer that measures magnetic flux in real space. We demonstrate the interferometer for a graphene-type hexagonal optical lattice loaded with bosonic atoms. By detecting the singular π Berry flux localized at each Dirac point, we establish the high momentum resolution of this interferometric technique. Our work forms the basis for a general framework to fully characterize topological band structures.
Fizeau`s experiment and the Aharonov--Bohm effect
Cook, R.J.; Fearn, H.; Milonni, P.W.
1995-08-01
The electromagnetic wave equations in a moving medium may be approximated by a form similar to that of the Schroedinger equation for a particle in an electromagnetic field, with the velocity {bold v} of the medium and the vorticity {del}{times}{bold v} playing the roles of the vector potential and magnetic field, re- spectively. A purely classical optical analogue of the Aharonov--Bohm effect follows by consider- ation of the interference pattern produced by two beams, each of which propagates in a region with zero vorticity, but such that the flux of the vorticity through the closed loop defined by the optical paths does not vanish. Fizeau`s experiment (1851) on the velocity of light in moving media may be regarded as an example of such a situation. {copyright} {ital 1995} {ital American} {ital Association} {ital of} {ital Physics} {ital Teachers}.
Uniform asymptotic formula for the Aharonov Bohm wavefield
NASA Astrophysics Data System (ADS)
Hannay, J. H.
2016-06-01
A uniform asymptotic formula for the Aharonov-Bohm wavefield (that of a plane quantum wave scattered by a thin straight solenoid) far away from the solenoid is obtained in a direct way. Actually quite good accuracy is achieved even down to one wavelength away. The error is numerically of order radius^(-3/2) for all values of polar angle, including directly forwards. Several previous formulas, uniform and otherwise, for the far field limit exist in the literature. All contain the essential ingredient: the Fresnel integral (complex error function), but ordinarily the error in these formulas is of order radius^(-1/2) in the forwards direction where the Fresnel contribution is most important.
Nonlinear Aharonov-Bohm Scattering by Optical Vortices
Neshev, Dragomir; Nepomnyashchy, Alexander; Kivshar, Yuri S.
2001-07-23
We study linear and nonlinear wave scattering by an optical vortex in a self-defocusing nonlinear Kerr medium. In the linear case, we find a splitting of a plane-wave front at the vortex proportional to its circulation, similar to what occurs in the scattered wave of electrons for the Aharonov-Bohm effect. For larger wave amplitudes, we study analytically and numerically the scattering of a dark-soliton stripe (a nonlinear analog of a small-amplitude wave packet) by a vortex and observe a significant asymmetry of the scattered wave. Subsequently, a wave-front splitting of the scattered wave develops into transverse modulational instability, ''unzipping'' the stripe into trains of vortices with opposite charges.
NASA Astrophysics Data System (ADS)
Nitta, Junsaku; Bergsten, Tobias
2008-03-01
Time reversal symmetric Al’tshuler-Aronov-Spivak (AAS) oscillations are measured in an array of InGaAs mesoscopic loops. We confirm that gate voltage dependence of h/2 e period oscillations is due to spin interference from the effect of ensemble average on the AAS and Aharonov-Bohm (AB) amplitudes. This spin interference is based on the time reversal Aharonov-Casher (AC) effect. The AC interference oscillations are controlled over several periods. This result shows evidence for electrical manipulation of the spin precession angle in an InGaAs two-dimensional electron gas channel. We control the precession rate in a precise and predictable way with an electrostatic gate.
On the relation between the Feynman paradox and the Aharonov-Bohm effects
NASA Astrophysics Data System (ADS)
McGregor, Scot; Hotovy, Ryan; Caprez, Adam; Batelaan, Herman
2012-09-01
The magnetic Aharonov-Bohm (A-B) effect occurs when a point charge interacts with a line of magnetic flux, while its reciprocal, the Aharonov-Casher (A-C) effect, occurs when a magnetic moment interacts with a line of charge. For the two interacting parts of these physical systems, the equations of motion are discussed in this paper. The generally accepted claim is that both parts of these systems do not accelerate, while Boyer has claimed that both parts of these systems do accelerate. Using the Euler-Lagrange equations we predict that in the case of unconstrained motion, only one part of each system accelerates, while momentum remains conserved. This prediction requires a time-dependent electromagnetic momentum. For our analysis of unconstrained motion, the A-B effects are then examples of the Feynman paradox. In the case of constrained motion, the Euler-Lagrange equations give no forces, in agreement with the generally accepted analysis. The quantum mechanical A-B and A-C phase shifts are independent of the treatment of constraint. Nevertheless, experimental testing of the above ideas and further understanding of the A-B effects that are central to both quantum mechanics and electromagnetism could be possible.
NASA Astrophysics Data System (ADS)
Wang, Dehua
2014-09-01
The Aharonov-Bohm (AB) effect in the photodetachment microscopy of the H- ions in an electric field has been studied on the basis of the semiclassical theory. After the H- ion is irradiated by a laser light, they provide a coherent electron source. When the detached electron is accelerated by a uniform electric field, two trajectories of a detached electron which run from the source to the same point on the detector, will interfere with each other and lead to an interference pattern in the photodetachment microscopy. After the solenoid is electrified beside the H- ion, even though no Lorentz force acts on the electron outside the solenoid, the photodetachment microscopy interference pattern on the detector is changed with the variation in the magnetic flux enclosed by the solenoid. This is caused by the AB effect. Under certain conditions, the interference pattern reaches the macroscopic dimensions and could be observed in a direct AB effect experiment. Our study can provide some predictions for the future experimental study of the AB effect in the photodetachment microscopy of negative ions.
Time-dependent Aharonov-Bohm effect on the noncommutative space
NASA Astrophysics Data System (ADS)
Ma, Kai; Wang, Jian-Hua; Yang, Huan-Xiong
2016-08-01
We study the time-dependent Aharonov-Bohm effect on the noncommutative space. Because there is no net Aharonov-Bohm phase shift in the time-dependent case on the commutative space, therefore, a tiny deviation from zero indicates new physics. Based on the Seiberg-Witten map we obtain the gauge invariant and Lorentz covariant Aharonov-Bohm phase shift in general case on noncommutative space. We find there are two kinds of contribution: momentum-dependent and momentum-independent corrections. For the momentum-dependent correction, there is a cancellation between the magnetic and electric phase shifts, just like the case on the commutative space. However, there is a non-trivial contribution in the momentum-independent correction. This is true for both the time-independent and time-dependent Aharonov-Bohm effects on the noncommutative space. However, for the time-dependent Aharonov-Bohm effect, there is no overwhelming background which exists in the time-independent Aharonov-Bohm effect on both commutative and noncommutative space. Therefore, the time-dependent Aharonov-Bohm can be sensitive to the spatial noncommutativity. The net correction is proportional to the product of the magnetic fluxes through the fundamental area represented by the noncommutative parameter θ, and through the surface enclosed by the trajectory of charged particle. More interestingly, there is an anti-collinear relation between the logarithms of the magnetic field B and the averaged flux Φ / N (N is the number of fringes shifted). This nontrivial relation can also provide a way to test the spatial noncommutativity. For BΦ / N ∼ 1, our estimation on the experimental sensitivity shows that it can reach the 10 GeV scale. This sensitivity can be enhanced by using stronger magnetic field strength, larger magnetic flux, as well as higher experimental precision on the phase shift.
Aharonov-Bohm conductance of a disordered single-channel quantum ring
NASA Astrophysics Data System (ADS)
Shmakov, P. M.; Dmitriev, A. P.; Kachorovskii, V. Yu.
2013-06-01
We study the effect of weak disorder on tunneling conductance of a single-channel quantum ring threaded by magnetic flux. We assume that the temperature is higher than the level spacing in the ring and smaller than the Fermi energy. In the absence of disorder, the conductance shows sharp dips (antiresonances) as a function of magnetic flux. We discuss different types of disorder and find that the short-range disorder broadens antiresonances, while the long-range one leads to the appearance of additional resonant dips. We demonstrate that the resonant dips have essentially non-Lorentzian shape. The results are generalized to account for the spin-orbit interaction, which leads to splitting of the disorder-broadened resonant dips, and consequently, to coexisting of two types of oscillations (both having the form of sharp dips): Aharonov-Bohm oscillations with magnetic flux and Aharonov-Casher oscillations with the strength of the spin-orbit coupling. We also discuss the effect of the Zeeman coupling.
Probe of hydrogen atom in plasmas with magnetic, electric, and Aharonov-Bohm flux fields
NASA Astrophysics Data System (ADS)
Bahar, M. K.; Soylu, A.
2016-09-01
In this study, for the first time, the combined effects of external magnetic, electric, and Aharonov-Bohm (AB) flux fields on quantum levels of the hydrogen atom embedded in Debye and quantum plasmas modeled by the more general exponential cosine screened Coulomb (MGECSC) potential are investigated within cylindrical coordinate formalism using the asymptotic iteration method. The MGECSC potential includes four different potential forms when considering different sets of the parameters in the potential. The corresponding Schrödinger equation is solved numerically in order to examine both strong and weak regimes and confinement effects of external fields. The influence of screening parameters of the MGECSC potential on quantum levels of the hydrogen atom is also studied in detail in the presence of external magnetic, electric, and AB flux fields. As it is possible to model both Debye and quantum plasmas by using screening parameters in the MGECSC potential, the effects of each plasma environment on quantum levels of the hydrogen atom are also considered in the external fields. It is observed that there are important results of external fields on the total interaction potential profile, and the most dominant one in these fields is the magnetic field. Furthermore, the effects of confinement on the physical state of the plasma environment is a subject of this study. These details would be important in experimental and theoretical investigations in plasma and atomic physics fields.
Peshkin, M.
1996-03-01
The electrons in a conductor surrounding an external magnetic field are acted on by a vector potential that cannot be removed by a gauge transformation. Nevertheless, a macroscopic normal conductor can experience no Aharonov-Bohm (AB) effect. That is proved by assuming only that a normal conductor lacks off-diagonal long-range order (ODLRO), which means that the electrons lack long-range phase coherence. Then by restricting the Hilbert space to density matrices which lack ODLRO, one can introduce a restricted gauge transformation that removes the interaction of the conductor with the vector potential. Consequently, the AB effect on a beam particle is not shielded by the conductor. {copyright} {ital 1996 The American Physical Society.}
NASA Astrophysics Data System (ADS)
Falaye, Babatunde James; Sun, Guo-Hua; Silva-Ortigoza, Ramón; Dong, Shi-Hai
2016-05-01
This study presents the confinement influences of Aharonov-Bohm (AB) flux and electric and magnetic fields directed along the z axis and encircled by quantum plasmas on the hydrogen atom. The all-inclusive effects result in a strongly attractive system while the localizations of quantum levels change and the eigenvalues decrease. We find that the combined effect of the fields is stronger than a solitary effect and consequently there is a substantial shift in the bound state energy of the system. We also find that to perpetuate a low-energy medium for the hydrogen atom in quantum plasmas, a strong electric field and weak magnetic field are required, whereas the AB flux field can be used as a regulator. The application of the perturbation technique utilized in this paper is not restricted to plasma physics; it can also be applied in molecular physics.
Falaye, Babatunde James; Sun, Guo-Hua; Silva-Ortigoza, Ramón; Dong, Shi-Hai
2016-05-01
This study presents the confinement influences of Aharonov-Bohm (AB) flux and electric and magnetic fields directed along the z axis and encircled by quantum plasmas on the hydrogen atom. The all-inclusive effects result in a strongly attractive system while the localizations of quantum levels change and the eigenvalues decrease. We find that the combined effect of the fields is stronger than a solitary effect and consequently there is a substantial shift in the bound state energy of the system. We also find that to perpetuate a low-energy medium for the hydrogen atom in quantum plasmas, a strong electric field and weak magnetic field are required, whereas the AB flux field can be used as a regulator. The application of the perturbation technique utilized in this paper is not restricted to plasma physics; it can also be applied in molecular physics.
A solenoidal synthetic field and the non-Abelian Aharonov-Bohm effects in neutral atoms
NASA Astrophysics Data System (ADS)
Huo, Ming-Xia; Nie, Wei; Hutchinson, David A. W.; Kwek, Leong Chuan
2014-08-01
Cold neutral atoms provide a versatile and controllable platform for emulating various quantum systems. Despite efforts to develop artificial gauge fields in these systems, realizing a unique ideal-solenoid-shaped magnetic field within the quantum domain in any real-world physical system remains elusive. Here we propose a scheme to generate a ``hairline'' solenoid with an extremely small size around 1 micrometer which is smaller than the typical coherence length in cold atoms. Correspondingly, interference effects will play a role in transport. Despite the small size, the magnetic flux imposed on the atoms is very large thanks to the very strong field generated inside the solenoid. By arranging different sets of Laguerre-Gauss (LG) lasers, the generation of Abelian and non-Abelian SU(2) lattice gauge fields is proposed for neutral atoms in ring- and square-shaped optical lattices. As an application, interference patterns of the magnetic type-I Aharonov-Bohm (AB) effect are obtained by evolving atoms along a circle over several tens of lattice cells. During the evolution, the quantum coherence is maintained and the atoms are exposed to a large magnetic flux. The scheme requires only standard optical access, and is robust to weak particle interactions.
A solenoidal synthetic field and the non-Abelian Aharonov-Bohm effects in neutral atoms.
Huo, Ming-Xia; Nie, Wei; Hutchinson, David A W; Kwek, Leong Chuan
2014-08-08
Cold neutral atoms provide a versatile and controllable platform for emulating various quantum systems. Despite efforts to develop artificial gauge fields in these systems, realizing a unique ideal-solenoid-shaped magnetic field within the quantum domain in any real-world physical system remains elusive. Here we propose a scheme to generate a "hairline" solenoid with an extremely small size around 1 micrometer which is smaller than the typical coherence length in cold atoms. Correspondingly, interference effects will play a role in transport. Despite the small size, the magnetic flux imposed on the atoms is very large thanks to the very strong field generated inside the solenoid. By arranging different sets of Laguerre-Gauss (LG) lasers, the generation of Abelian and non-Abelian SU(2) lattice gauge fields is proposed for neutral atoms in ring- and square-shaped optical lattices. As an application, interference patterns of the magnetic type-I Aharonov-Bohm (AB) effect are obtained by evolving atoms along a circle over several tens of lattice cells. During the evolution, the quantum coherence is maintained and the atoms are exposed to a large magnetic flux. The scheme requires only standard optical access, and is robust to weak particle interactions.
The role of Coulomb interaction in thermoelectric effects of an Aharonov-Bohm interferometer.
Liu, Yu-Shen; Zhang, De-Bao; Yang, Xi-Feng; Feng, Jin-Fu
2011-06-03
We investigate the thermoelectric effects of an Aharonov-Bohm (AB) interferometer with a quantum dot (QD) embedded in each of its arms, where the intra-dot Coulomb interaction between electrons in each QD is taken into account. Using Green's function methods and the equation of motion (EOM) technique, we find that the Seebeck coefficient and Lorenz number can be strongly enhanced when the chemical potential sweeps the molecular states associated with the Fano line-shapes in the transmission spectra, due to quantum interference effects between the bonding and antibonding molecular states. It is found that enhancement of the thermoelectric effects occurs between the two groups of conductance peaks in the presence of strong intra-dot Coulomb interaction-the reason being that a transmission node is developed in the Coulomb blockade regime. In this case, the maximum value of the Lorenz number approaches 10π(2)k(B)(2)/(3e(2)). Its thermoelectric conversion efficiency in the absence of phonon thermal conductance, described by the figure of merit ZT, approaches 2 at room temperature. Therefore, it may be used as a high-efficiency solid-state thermoelectric conversion device under certain circumstances.
A solenoidal synthetic field and the non-Abelian Aharonov-Bohm effects in neutral atoms
Huo, Ming-Xia; Nie, Wei; Hutchinson, David A. W.; Kwek, Leong Chuan
2014-01-01
Cold neutral atoms provide a versatile and controllable platform for emulating various quantum systems. Despite efforts to develop artificial gauge fields in these systems, realizing a unique ideal-solenoid-shaped magnetic field within the quantum domain in any real-world physical system remains elusive. Here we propose a scheme to generate a “hairline” solenoid with an extremely small size around 1 micrometer which is smaller than the typical coherence length in cold atoms. Correspondingly, interference effects will play a role in transport. Despite the small size, the magnetic flux imposed on the atoms is very large thanks to the very strong field generated inside the solenoid. By arranging different sets of Laguerre-Gauss (LG) lasers, the generation of Abelian and non-Abelian SU(2) lattice gauge fields is proposed for neutral atoms in ring- and square-shaped optical lattices. As an application, interference patterns of the magnetic type-I Aharonov-Bohm (AB) effect are obtained by evolving atoms along a circle over several tens of lattice cells. During the evolution, the quantum coherence is maintained and the atoms are exposed to a large magnetic flux. The scheme requires only standard optical access, and is robust to weak particle interactions. PMID:25103877
The Aharonov-Bohm effect in Möbius rings
NASA Astrophysics Data System (ADS)
Li, Zehao; Ram-Mohan, L.; CenterComputational NanoScience Team
2013-03-01
Electron transmission through finite-width 2D ring structures is calculated for cylindrical, flat (Aharonov-Bohm), and Möbius rings. In the presence of an external magnetic field, curves of constructive transmission display a pattern similar to that for a 1D ring. The periodicity in the magnetic flux, in units of h / e , is weakly broken on 2D rings of finite width, so that a description with a 1D-path is very acceptable. The unusual states with half-integer values of
Paradoxes of the Aharonov-Bohm and the Aharonov-Casher Effects
NASA Astrophysics Data System (ADS)
Vaidman, Lev
For a believer in locality of Nature, the Aharonov-Bohm effect and the Aharonov-Casher effect are paradoxes. I discuss these and other Aharonov's paradoxes and propose a local explanation of these effects. If the solenoid in the Aharonov-Bohm effect is treated quantum mechanically, the effect can be explained via local interaction between the field of the electron and the solenoid. I argue that the core of the Aharonov-Bohm and the Aharonov-Casher effects is that of quantum entanglement: the quantum wave function describes all systems together. [Editor's note: for a video of the talk given by Prof. Vaidman at the Aharonov-80 conference in 2012 at Chapman University, see http://quantum.chapman.edu/talk-21.
Two-dimensional quantum ring in a graphene layer in the presence of a Aharonov-Bohm flux
NASA Astrophysics Data System (ADS)
Amaro Neto, José; Bueno, M. J.; Furtado, Claudio
2016-10-01
In this paper we study the relativistic quantum dynamics of a massless fermion confined in a quantum ring. We use a model of confining potential and introduce the interaction via Dirac oscillator coupling, which provides ring confinement for massless Dirac fermions. The energy levels and corresponding eigenfunctions for this model in graphene layer in the presence of Aharonov-Bohm flux in the centre of the ring and the expression for persistent current in this model are derived. We also investigate the model for quantum ring in graphene layer in the presence of a disclination and a magnetic flux. The energy spectrum and wave function are obtained exactly for this case. We see that the persistent current depends on parameters characterizing the topological defect.
The Berry phase and the Aharonov-Bohm effect on optical activity.
Tan, C Z
2008-09-15
The helical crystal structure in optically active media acts as the natural micro-solenoids for the electromagnetic waves passing through them, producing the longitudinal magnetic field in the direction of the axis of helices. Magnetic flux through the helical structure is quantized. The Berry phase is induced by rotation of the electrons around the helical structure. Optical rotation is related to the difference in the accumulative Berry phase between the right-, and the left-circularly polarized waves, which is proportional to the magnetic flux through the helical structure, according to the Aharonov-Bohm effect. The optical activity is the natural Faraday effect and the natural Aharonov-Bohm effect.
Optical signatures of the Aharonov-Bohm phase in single-walled carbon nanotubes.
Zaric, Sasa; Ostojic, Gordana N; Kono, Junichiro; Shaver, Jonah; Moore, Valerie C; Strano, Michael S; Hauge, Robert H; Smalley, Richard E; Wei, Xing
2004-05-21
We report interband magneto-optical spectra for single-walled carbon nanotubes in high magnetic fields up to 45 tesla, confirming theoretical predictions that the band structure of a single-walled carbon nanotube is dependent on the magnetic flux phi threading the tube. We have observed field-induced optical anisotropy as well as red shifts and splittings of absorption and photoluminescence peaks. The amounts of shifts and splittings depend on the value of phi/phi(0) and are quantitatively consistent with theories based on the Aharonov-Bohm effect. These results represent evidence of the influence of the Aharonov-Bohm phase on the band gap of a solid.
Cloaking of matter waves under the global Aharonov-Bohm effect
Lin, D.-H.; Luan, P.-G.
2009-05-15
We discuss the Aharonov-Bohm effect of a magnetic flux for its influence on a two-dimensional quantum cloak. It is shown that the matter wave of a charged particle under the global influence of the Aharonov-Bohm effect can still be perfectly cloaked and guided by the quantum cloak. Since the presence of the global influence of a magnetic flux on charged particles is universal, the perfect cloaking and guiding nature not only provides an ideal setup to cloak an object from matter waves but also provides an ideal setup to test the global physics of charged matter waves in the presence of a bare magnetic flux.
Photon mass and quantum effects of the Aharonov-Bohm type
Spavieri, G.; Rodriguez, M.
2007-05-15
The magnetic field due to the photon rest mass m{sub ph} modifies the standard results of the Aharonov-Bohm effect for electrons, and of other recent quantum effects. For the effect involving a coherent superposition of beams of particles with opposite electromagnetic properties, by means of a tabletop experiment, the limit m{sub ph}{approx_equal}10{sup -51} g is achievable, improving by 6 orders of magnitude that derived by Boulware and Deser for the Aharonov-Bohm effect.
The Aharonov-Bohm Effect and the Non-Locality Debate
NASA Astrophysics Data System (ADS)
Kennedy, John Bernard, Jr.
The Aharonov-Bohm effect is a celebrated quantum mechanical effect which some have claimed is an example of non-locality, i.e., of action at a distance. This thesis examines the theory and experimental tests of the effect, and compares it to another supposed example of non-locality, the EPR correlations. The role of the electromagnetic potentials in the quantum formalism, and especially gauge invariance and the physical significance of the vector potential, is detailed. I argue that K. H. Yang's proofs of the gauge arbitrariness of the conventional formalism are mistaken. Four central and conflicting theories of the AB effect are reviewed and critiqued: (i) physically significant potentials, (ii) local effects of electromagnetic fluxes, (iii) multi-valued wave functions, and (iv) non-locality. An entire chapter is devoted to the topological interpretations of the effect which model the potentials as connections in higher-dimensional fiber bundle geometries. The relation between the AB effect and geometric phase phenomena, like Berry's phase, is studied. The new geometric models inherit the merits and demerits of the potentials interpretation. The quantum no-signalling proofs for the case of the EPR-Bohm-Bell experiments are analyzed and unified in a single theorem: they are simple consequences of the tenstor product representation of combined quantum systems. All proposed local theories of the AB effect are finally unsatisfactory--for a variety of reasons. However, given the lack of a clear criterion for non-locality, there are no decisive grounds for the claim that the AB effect is non-local.
Periodic Magnetoresistance Oscillations in Side-Gated Quantum Dots
2006-01-01
wavelength, resulting in an oscillatory structure in the conductance. Under magnetic fields, Aharonov - Bohm -type oscillations are also predicted in a...mainly determined by the quantum-dot length. This suggests that the oscillation is not associated with the Aharonov - Bohm -type effects. In Fig. 7, we
NASA Astrophysics Data System (ADS)
Fomin, V. M.; Gladilin, V. N.; Klimin, S. N.; Devreese, J. T.; Kleemans, N. A. J. M.; Koenraad, P. M.
2007-12-01
We analyze theoretically the electron energy spectrum and the magnetization of an electron in a strained InxGa1-xAs/GaAs self-assembled quantum ring (SAQR) with realistic parameters, determined from the cross-sectional scanning-tunneling microscopy characterization of that nanostructure. The SAQRs have an asymmetric indium-rich craterlike shape with a depression rather than an opening at the center. Although the real SAQR shape differs strongly from an idealized circular-symmetric open ring structure, the Aharonov-Bohm oscillations of the magnetization survive.
Duality in the Aharonov-Casher and Aharonov-Bohm effects
NASA Astrophysics Data System (ADS)
Rohrlich, Daniel
2010-09-01
A neutral particle with a magnetic moment interacts with a charged particle. Such an interaction is invariant under the interchange of the particles. This interchangeability or duality of the particles elucidates subtleties of the Aharonov-Bohm and Aharonov-Casher effects, including whether and how these two effects are themselves dual.
Exact Green's function of the Aharonov-Bohm-Coulomb system via the Feynman-Kac formula
NASA Astrophysics Data System (ADS)
Chuu, Der-San; Lin, De-Hone
1999-10-01
The Green's function of the relativistic Aharonov-Bohm-Coulomb system is given by the Feynman-Kac formula. The earlier treatment is based on the multiple-valued transformation of Levi-Civitá. The method used in this contribution involves only the explicit form of a simple Green's function and an explicit path integral is avoided.
Electron-positron pair production in the Aharonov-Bohm potential
Skarzhinsky, V.D. |; Audretsch, J.; Jasper, U.
1996-02-01
In the framework of QED we evaluate the cross section for electron-positron pair production by a single photon in the presence of the external Aharonov-Bohm potential in first order of perturbation theory. We analyze energy, angular, and polarization distributions at different energy regines: near the threshold and at high photon energies. {copyright} {ital 1996 The American Physical Society.}
Stokes' theorem, gauge symmetry and the time-dependent Aharonov-Bohm effect
Macdougall, James Singleton, Douglas
2014-04-15
Stokes' theorem is investigated in the context of the time-dependent Aharonov-Bohm effect—the two-slit quantum interference experiment with a time varying solenoid between the slits. The time varying solenoid produces an electric field which leads to an additional phase shift which is found to exactly cancel the time-dependent part of the usual magnetic Aharonov-Bohm phase shift. This electric field arises from a combination of a non-single valued scalar potential and/or a 3-vector potential. The gauge transformation which leads to the scalar and 3-vector potentials for the electric field is non-single valued. This feature is connected with the non-simply connected topology of the Aharonov-Bohm set-up. The non-single valued nature of the gauge transformation function has interesting consequences for the 4-dimensional Stokes' theorem for the time-dependent Aharonov-Bohm effect. An experimental test of these conclusions is proposed.
The Aharonov-Bohm effect and its applications to electron phase microscopy.
Tonomura, Akira
2006-04-01
The Aharonov-Bohm effect was conclusively established by a series of our electron interference experiments, with the help of some advanced techniques, such as coherent field-emission electron beams and microlithography. Using this fundamental principle behind the interaction of an electron wave with electromagnetic fields, new observation techniques were developed to directly observe microscopic objects and quantum phenomena previously unobservable.
Spin-charge separation in Aharonov-Bohm rings of interacting electrons.
Hallberg, K; Aligia, A A; Kampf, A P; Normand, B
2004-08-06
We investigate the properties of strongly correlated electronic models on a flux-threaded ring connected to semi-infinite free-electron leads. The interference pattern of such an Aharonov-Bohm ring shows sharp dips at certain flux values, determined by the filling, which are a consequence of spin-charge separation in a nanoscopic system.
Aharonov-Bohm and Berry phases for a quantum cloud of charge
Aharonov, Y.; Coleman, S.; Goldhaber, A.S.; Nussinov, S.; Popescu, S.; Reznik, B.; Rohrlich, D.; Vaidman, L. Lyman Laboratory, Harvard University, Cambridge, Massachusetts 02138 Institute for Theoretical Physics, State University of New York, Stony Brook, New York 11794-3840 Service de Physique Theorique, Universite Libre de Bruxelles, Campus Plaine, C.P. 225, Boulevard du Triomphe, B-1050 Brussels )
1994-08-15
We investigate the phase accumulated by a charged particle in an extended quantum state as it encircles one or more magnetic fluxons, each carrying half a flux unit. A simple, essentially topological analysis reveals an interplay between the Aharonov-Bohm phase and Berry's phase.
Nucleon statistics in holographic QCD: Aharonov-Bohm effect in a matrix model
Hashimoto, Koji; Iizuka, Norihiro
2010-11-15
We show that the Aharonov-Bohm effect in the nuclear matrix model [K. Hashimoto, N. Iizuka, and P. Yi, J. High Energy Phys. 10 (2010), 3.] derives the statistical nature of nucleons in holographic QCD. For N{sub c}=odd (even), the nucleon is shown to be a fermion (boson).
Line of magnetic monopoles and an extension of the Aharonov-Bohm effect
NASA Astrophysics Data System (ADS)
Chee, J.; Lu, W.
2016-10-01
In the Landau problem on the two-dimensional plane, physical displacement of a charged particle (i.e., magnetic translation) can be induced by an in-plane electric field. The geometric phase accompanying such magnetic translation around a closed path differs from the topological phase of Aharonov and Bohm in two essential aspects: The particle is in direct contact with the magnetic field and the geometric phase has an opposite sign from the Aharonov-Bohm phase. We show that magnetic translation on the two-dimensional cylinder implemented by the Schrödinger time evolution truly leads to the Aharonov-Bohm effect. The magnetic field normal to the cylinder's surface corresponds to a line of magnetic monopoles of uniform density whose simulation is currently under investigation in cold atom physics. In order to characterize the quantum problem, one needs to specify the value of the magnetic flux (modulo the flux unit) that threads but not in touch with the cylinder. A general closed path on the cylinder may enclose both the Aharonov-Bohm flux and the local magnetic field that is in direct contact with the charged particle. This suggests an extension of the Aharonov-Bohm experiment that naturally takes into account both the geometric phase due to local interaction with the magnetic field and the topological phase of Aharonov and Bohm.
Nucleon statistics in holographic QCD: Aharonov-Bohm effect in a matrix model
NASA Astrophysics Data System (ADS)
Hashimoto, Koji; Iizuka, Norihiro
2010-11-01
We show that the Aharonov-Bohm effect in the nuclear matrix model [K. Hashimoto, N. Iizuka, and P. Yi, J. High Energy Phys.JHEPFG1029-8479 10 (2010), 3.10.1007/JHEP10(2010)003] derives the statistical nature of nucleons in holographic QCD. For Nc=odd (even), the nucleon is shown to be a fermion (boson).
The Aharonov-Bohm effect and Tonomura et al. experiments: Rigorous results
Ballesteros, Miguel; Weder, Ricardo
2009-12-15
The Aharonov-Bohm effect is a fundamental issue in physics. It describes the physically important electromagnetic quantities in quantum mechanics. Its experimental verification constitutes a test of the theory of quantum mechanics itself. The remarkable experiments of Tonomura et al. ['Observation of Aharonov-Bohm effect by electron holography', Phys. Rev. Lett 48, 1443 (1982) and 'Evidence for Aharonov-Bohm effect with magnetic field completely shielded from electron wave', Phys. Rev. Lett 56, 792 (1986)] are widely considered as the only experimental evidence of the physical existence of the Aharonov-Bohm effect. Here we give the first rigorous proof that the classical ansatz of Aharonov and Bohm of 1959 ['Significance of electromagnetic potentials in the quantum theory', Phys. Rev. 115, 485 (1959)], that was tested by Tonomura et al., is a good approximation to the exact solution to the Schroedinger equation. This also proves that the electron, that is, represented by the exact solution, is not accelerated, in agreement with the recent experiment of Caprez et al. in 2007 ['Macroscopic test of the Aharonov-Bohm effect', Phys. Rev. Lett. 99, 210401 (2007)], that shows that the results of the Tonomura et al. experiments can not be explained by the action of a force. Under the assumption that the incoming free electron is a Gaussian wave packet, we estimate the exact solution to the Schroedinger equation for all times. We provide a rigorous, quantitative error bound for the difference in norm between the exact solution and the Aharonov-Bohm Ansatz. Our bound is uniform in time. We also prove that on the Gaussian asymptotic state the scattering operator is given by a constant phase shift, up to a quantitative error bound that we provide. Our results show that for intermediate size electron wave packets, smaller than the ones used in the Tonomura et al. experiments, quantum mechanics predicts the results observed by Tonomura et al. with an error bound smaller than 10
NASA Astrophysics Data System (ADS)
Chen, Xiong-Wen; Shi, Zhen-Gang; Song, Ke-Hui
2009-11-01
We theoretically investigate the Kondo effect of a quantum dot embedded in a mesoscopic Aharonov-Bohm (AB) ring in the presence of the spin flip processes by means of the one-impurity Anderson Hamiltonian. Based on the slave-boson mean-field theory, we find that in this system the persistent current (PC) sensitively depends on the parity and size of the AB ring and can be tuned by the spin-flip scattering (R). In the small AB ring, the PC is suppressed due to the enhancing R weakening the Kondo resonance. On the contrary, in the large AB ring, with R increasing, the peak of PC firstly moves up to max-peak and then down. Especially, the PC phase shift of π appears suddenly with the proper value of R, implying the existence of the anomalous Kondo effect in this system. Thus this system may be a candidate for quantum switch.
Graphene under the influence of Aharonov-Bohm flux and constant magnetic field
NASA Astrophysics Data System (ADS)
Stepanov, E. A.; Zhukovsky, V. Ch.
2016-09-01
Investigation of real two-dimensional systems with Dirac-like electronic behavior under the influence of magnetic field is challenging and leads to many interesting physical results. In this paper we study a 2D graphene model with a particular form of magnetic field as a superposition of a homogeneous field and an Aharonov-Bohm vortex. For this configuration, electronic wave functions and the energy spectrum are obtained and it is shown that the magnetic Aharonov-Bohm vortex plays the role of a charge impurity. As a demonstration of vacuum properties of the system, vacuum current, as well as an electric current, is calculated and their representation for particular limiting cases of a magnetic field is obtained.
Vortex degeneracy lifting and Aharonov-Bohm-like interference in deformed photonic graphene.
Zhang, Peng; Gallardo, Daniel; Liu, Sheng; Gao, Yuanmei; Li, Tongcang; Wang, Yuan; Chen, Zhigang; Zhang, Xiang
2017-03-01
Photonic graphene, a honeycomb lattice of evanescently coupled waveguides, has provided a superior platform for investigating a host of fundamental phenomena such as unconventional edge states, synthetic magnetic fields, photonic Landau levels, Floquet topological insulators, and pseudospin effects. Here, we demonstrate both experimentally and numerically, topological vortex degeneracy lifting and Aharonov-Bohm-like interference from local deformation in a photonic honeycomb lattice. When a single valley is excited, lattice deformation leads to the generation of a vortex pair due to the lifting of degeneracy associated with pseudospin states. In the case of double-valley excitation, we observe the Aharonov-Bohm-like interference merely due to the deformation of the graphene lattice, which gives rise to an artificial gauge field. Our results may provide insight into the understanding of similar phenomena in other graphene-like materials and structures.
Aharonov-Bohm interference and beating in single-walled carbon-nanotube interferometers.
Cao, Jien; Wang, Qian; Rolandi, Marco; Dai, Hongjie
2004-11-19
Relatively low magnetic fields applied parallel to the axis of a chiral single-walled carbon nanotube are found causing large modulations to the p channel or valence band conductance of the nanotube in the Fabry-Perot interference regime. Beating in the Aharonov-Bohm type of interference between two field-induced nondegenerate subbands of spiraling electrons is responsible for the observed modulation with a pseudoperiod much smaller than that needed to reach the flux quantum Phi0 = h/e through the nanotube cross section. We show that single-walled nanotubes represent the smallest cylinders exhibiting the Aharonov-Bohm effect with rich interference and beating phenomena arising from well-defined molecular orbitals reflective of the nanotube chirality.
Spin accumulation assisted by the Aharonov-Bohm-Fano effect of quantum dot structures.
Gong, Wei-Jiang; Han, Yu; Wei, Guo-Zhu; Du, An
2012-09-17
: We investigate the spin accumulations of Aharonov-Bohm interferometers with embedded quantum dots by considering spin bias in the leads. It is found that regardless of the interferometer configurations, the spin accumulations are closely determined by their quantum interference features. This is mainly manifested in the dependence of spin accumulations on the threaded magnetic flux and the nonresonant transmission process. Namely, the Aharonov-Bohm-Fano effect is a necessary condition to achieve the spin accumulation in the quantum dot of the resonant channel. Further analysis showed that in the double-dot interferometer, the spin accumulation can be detailedly manipulated. The spin accumulation properties of such structures offer a new scheme of spin manipulation. When the intradot Coulomb interactions are taken into account, we find that the electron interactions are advantageous to the spin accumulation in the resonant channel.
Aharonov-Bohm effect and resonances in the circular quantum billiard with two leads
Ree, S.; Reichl, L.E.
1999-03-01
We calculate the conductance through a circular quantum billiard with two leads and a point magnetic flux at the center. The boundary element method is used to solve the Schr{umlt o}dinger equation of the scattering problem, and the Landauer formula is used to calculate the conductance from the transmission coefficients. We use two different shapes of leads, straight and conic, and find that the conductance is affected by lead geometry, the relative positions of the leads and the magnetic flux. The Aharonov-Bohm effect can be seen from shifts and splittings of fluctuations. When the flux is equal to h/2e and the angle between leads is 180{degree}, the conductance tends to be suppressed to zero in the low-energy range due to the Aharonov-Bohm effect. {copyright} {ital 1999} {ital The American Physical Society}
Aharonov-Bohm effect in quantum-to-classical correspondence of the Heisenberg principle
Lin, D.-H.; Chang, J.-G.; Hwang, C.-C.
2003-04-01
The exact energy spectrum and wave function of a charged particle moving in the Coulomb field and Aharonov-Bohm's magnetic flux are solved by the nonintegrable phase factor. The universal formula for the matrix elements of the radial operator r{sup {alpha}} of arbitrary power {alpha} is given by an analytical solution. The difference between the classical limit of matrix elements of inverse radius in quantum mechanics and the Fourier components of the corresponding quantity for the pure Coulomb system in classical mechanics is examined in reference to the correspondence principle of Heisenberg. Explicit calculation shows that the influence of nonlocal Aharonov-Bohm effect exists even in the classical limit. The semiclassical quantization rule for systems containing the topological effect is presented in the light of Heisenberg's corresponding principle.
Noncommutative correction to Aharonov-Bohm scattering: A field theory approach
Anacleto, M.A.; Gomes, M.; Silva, A.J. da; Spehler, D.
2004-10-15
We study a noncommutative nonrelativistic theory in 2+1 dimensions of a scalar field coupled to the Chern-Simons field. In the commutative situation this model has been used to simulate the Aharonov-Bohm effect in the field theory context. We verified that, contrary to the commutative result, the inclusion of a quartic self-interaction of the scalar field is not necessary to secure the ultraviolet renormalizability of the model. However, to obtain a smooth commutative limit the presence of a quartic gauge invariant self-interaction is required. For small noncommutativity we fix the corrections to the Aharonov-Bohm scattering and prove that up to one loop the model is free from dangerous infrared/ultraviolet divergences.
Scattering theory and the Aharonov-Bohm effect in quasiclassical physics
Sitenko, Yurii A.; Vlasii, Nadiia D.
2011-06-15
Research Highlights: > Scattering Aharonov-Bohm effect. > Short-wavelength limit of scattered nonrelativistic particles. > Fraunhofer diffraction in the forward direction. > Fresnel diffraction in the forward region in conical space. > Enclosed magnetic flux is a gate for the propagation of quasiclassical particles. - Abstract: Scattering of a nonrelativistic quantum-mechanical particle by an impenetrable magnetic vortex is considered. The nonvanishing transverse size of the vortex is taken into account, and the limit of short, as compared to this size, wavelengths of the scattered particle is analyzed. We show that the scattering Aharonov-Bohm effect persists in the quasiclassical limit owing to the diffraction persisting in the short-wavelength limit. As a result, the vortex flux serves as a gate for the propagation of short-wavelength, almost classical, particles. This quasiclassical effect is more feasible to experimental detection in the case when space outside the vortex is conical.
How the Test of Aharonov-Bohm Effect Was Initiated at Hitachi Laboratory
NASA Astrophysics Data System (ADS)
Osakabe, Nobuyuki
2014-01-01
I joined the Tonomura's team in 1980. Since then, I have seen his enthusiasm and creativity in science as a member of his team and later as director of the laboratory. I will discuss in this article how the industrially driven technologies met science at Hitachi Central Research Laboratory in the case of verification of the Aharonov-Bohm effect and other scientific achievements by Akira Tonomura.
Atomic multiple-wave interferometer phase-shifted by the scalar Aharonov-Bohm effect
Aoki, Takatoshi; Yasuhara, Makoto; Morinaga, Atsuo
2003-05-01
A time-domain atomic multiple-wave interferometer using laser-cooled and trapped sodium atoms has been developed under pulsed magnetic fields. Each atomic phase was shifted due to the scalar Aharonov-Bohm effect by applying spatially homogeneous pulsed magnetic fields between numerous Raman excitation laser pulses. Interference fringes with a finesse of 11 were demonstrated for 11 successive Raman pulses and ten magnetic-field pulses.
High-temperature Aharonov-Bohm effect in transport through a single-channel quantum ring
NASA Astrophysics Data System (ADS)
Dmitriev, A. P.; Gornyi, I. V.; Kachorovskii, V. Yu.; Polyakov, D. G.; Shmakov, P. M.
2015-02-01
We overview transport properties of an Aharonov-Bohm interferometer made of a single-channel quantum ring. Remarkably, in this setup, essentially quantum effects survive thermal averaging: the high-temperature tunneling conductance G of a ring shows sharp dips (antiresonances) as a function of magnetic flux. We discuss effects of the electron-electron interaction, disorder, and spin-orbit coupling on the Aharonov-Bohm transport through the ring. The interaction splits the dip into series of dips broadened by dephasing. The physics behind this behavior is the persistent-current-blockade: the current through the ring is blocked by the circular current inside the ring. Dephasing is then dominated by tunneling-induced fluctuations of the circular current. The short-range disorder broadens antiresonances, while the long-range one induces additional dips. In the presence of a spin-orbit coupling, G exhibits two types of sharp antiresonances: Aharonov-Bohm and Aharonov-Casher ones. In the vicinity of the antiresonances, the tunneling electrons acquire spin polarization, so that the ring serves as a spin polarizer.
Effects of nongauge potentials on the spin-1/2 Aharonov-Bohm problem
Hagen, C.R. )
1993-12-15
Some recent work has attempted to show that the singular solutions which are known to occur in the Dirac description of spin-1/2 Aharonov-Bohm scattering can be eliminated by the inclusion of strongly repulsive potentials inside the flux tube. It is shown here that these calculations are generally unreliable since they necessarily require potentials which lead to the occurrence of Klein's paradox. To avoid that difficulty the problem is solved within the framework of the Galilean spin-1/2 wave equation which is free of that particular complication. It is then found that the singular solutions can be eliminated provided that the nongauge potential is made energy dependent. The effect of the inclusion of a Coulomb potential is also considered with the result being that the range of flux parameter for which singular solutions are allowed is only one-half as great as in the pure Aharonov-Bohm limit. Expressions are also obtained for the binding energies which can occur in the combined Aharonov-Bohm-Coulomb system.
NASA Astrophysics Data System (ADS)
Rodríguez Prada, F. A.; Gutiérrez, W.; Mikhailov, I. D.
2017-01-01
The effect of the external magnetic field on the spectral properties of one-electron non-uniform quantum ring with radially directed hills is analysed. The corresponding one-particle wave equation is separable in the adiabatic limit, when the layer thickness is essentially smaller than its lateral dimension. Our calculations show that the presence of a single axially directed hill as well as a rise of the central hole thickness produce a quenching of the Aharonov-Bohm (AB) oscillations of the lower energy levels and of the magnetic momentum. However, as the number of radially directed hills is increased, the system exhibits again oscillations, resulted from an enhancement of tunnelling circular currents.
Scattering of spin 1/2 particles by the 2+1 dimensional noncommutative Aharonov-Bohm potential
Ferrari, A. F.; Gomes, M.; Stechhahn, C. A.
2007-10-15
In this work we study modifications in the Aharonov-Bohm effect for relativistic spin 1/2 particles due to the noncommutativity of spacetime in 2+1 dimensions. The noncommutativity gives rise to a correction to the Aharonov-Bohm potential which is highly singular at the origin, producing divergences in a perturbative expansion around the usual solution of the free Dirac equation. This problem is surmounted by using a perturbative expansion around the exact solution of the commutative Aharonov-Bohm problem. We calculate, in this setting, the scattering amplitude and the corrections to the differential and total cross sections for a spin 1/2 particle, in the small-flux limit.
Eckle, H.-P.; Johannesson, H.; Stafford, C. A.
2001-07-02
We study the persistent currents induced by both the Aharonov-Bohm and Aharonov-Casher effects in a one-dimensional mesoscopic ring coupled to a sidebranch quantum dot at Kondo resonance. For privileged values of the Aharonov-Bohm-Casher fluxes, the problem can be mapped onto an integrable model, exactly solvable by a Bethe ansatz. In the case of a pure magnetic Aharonov-Bohm flux, we find that the presence of the quantum dot has no effect on the persistent current. In contrast, the Kondo resonance interferes with the spin-dependent Aharonov-Casher effect to induce a current which, in the strong-coupling limit, is independent of the number of electrons in the ring.
Eckle, H P; Johannesson, H; Stafford, C A
2001-07-02
We study the persistent currents induced by both the Aharonov-Bohm and Aharonov-Casher effects in a one-dimensional mesoscopic ring coupled to a sidebranch quantum dot at Kondo resonance. For privileged values of the Aharonov-Bohm-Casher fluxes, the problem can be mapped onto an integrable model, exactly solvable by a Bethe ansatz. In the case of a pure magnetic Aharonov-Bohm flux, we find that the presence of the quantum dot has no effect on the persistent current. In contrast, the Kondo resonance interferes with the spin-dependent Aharonov-Casher effect to induce a current which, in the strong-coupling limit, is independent of the number of electrons in the ring.
NASA Astrophysics Data System (ADS)
Filgueiras, Cleverson; Rojas, Moises; Aciole, Gilson; Silva, Edilberto O.
2016-11-01
We investigate the influence of a screw dislocation on the energy levels and the wavefunctions of an electron confined in a two-dimensional pseudoharmonic quantum dot under the influence of an external magnetic field inside a dot and Aharonov-Bohm field inside a pseudodot. The exact solutions for energy eigenvalues and wavefunctions are computed as functions of applied uniform magnetic field strength, Aharonov-Bohm flux, magnetic quantum number and the parameter characterizing the screw dislocation, the Burgers vector. We investigate the modifications due to the screw dislocation on the light interband absorption coefficient and absorption threshold frequency. Two scenarios are possible, depending on if singular effects either manifest or not. We found that as the Burgers vector increases, the curves of frequency are pushed up towards of the growth of it. One interesting aspect which we have observed is that the Aharonov-Bohm flux can be tuned in order to cancel the screw effect of the model.
NASA Astrophysics Data System (ADS)
Kondo, Kenji
2016-01-01
Many researchers have reported on spin filters using linear Rashba spin-orbit interactions (SOI). However, spin filters using square and cubic Rashba SOIs have not yet been reported. We consider that this is because the Aharonov-Casher (AC) phases acquired under square and cubic Rashba SOIs are ambiguous. In this study, we try to derive the AC phases acquired under square and cubic Rashba SOIs from the viewpoint of non-Abelian SU(2) gauge theory. These AC phases can be derived successfully from the non-Abelian SU(2) gauge theory without the completing square methods. Using the results, we investigate the spin filtering in a double quantum dot (QD) Aharonov-Bohm (AB) ring under linear, square, and cubic Rashba SOIs. This AB ring consists of elongated QDs and quasi-one-dimensional quantum nanowires under an external magnetic field. The spin transport is investigated from the left nanowire to the right nanowire in the above structure within the tight-binding approximation. In particular, we focus on the difference of spin filtering among linear, square, and cubic Rashba SOIs. The calculation is performed for the spin polarization by changing the penetrating magnetic flux for the AB ring subject to linear, square, and cubic Rashba SOIs. It is found that perfect spin filtering is achieved for all of the Rashba SOIs. This result indicates that this AB ring under general Rashba SOIs can be a promising device for spin current generation. Moreover, the AB rings under general Rashba SOIs behave in totally different ways in response to penetrating magnetic flux, which is attributed to linear, square, and cubic behaviors in the in-plane momentum. This result enables us to make a clear distinction between linear, square, and cubic Rashba SOIs according to the peak position of the perfect spin filtering.
NASA Astrophysics Data System (ADS)
Wu, C. H.; Tran, L.; Cain, C. A.
2012-05-01
Electron transport and the exact scaling relations for two irreducibly coupled Aharonov-Bohm (AB) rings with two external terminals attached are investigated. In coupled AB rings, a center common path exists where the phase of the electron wave function can be modulated by two applied fluxes simultaneously. The two coupled rings can be considered as two coupled atoms where Fermi level crossings exist not only between bonding states but also between bonding and anti-bonding states when the applied flux is varied in one of the two cases studied. We show that when the smallest atomic-sized coupled rings are scaled up any odd number of times, an identical electron transmission is preserved. When two terminals are attached to isolated coupled AB rings, there is a further redistribution of bond-charge stored within the center common path. The shift of the electron charge distribution to favor one end of the common path is accompanied by the redistribution of the two partial waves that traverse through the two arms from the input to the output terminal. The flux can control which arm the electron traverses through more favorably, and hence, the center path behaves like a flux-controlled charge reservoir for the electron transport. The unbalanced charge in the entire structure creates a space-charge effect much like a p-n junction. The paradox of the delocalization of the electron wave when two AB rings are coupled and the subsequent localization effect of the electron transport in a quantum network are described.
The Analogue of the Aharonov-Bohm Effect for Bound States for Neutral Particles
NASA Astrophysics Data System (ADS)
Bakke, Knut; Furtado, C.
We study the analogue of the Aharonov-Bohm effect for bound states for a neutral particle with a permanent magnetic dipole moment interacting with an external field. We consider a neutral particle confined to moving between two coaxial cylinders and show the dependence of the energy levels on the Aharonov-Casher quantum flux. Moreover, we show that the same flux dependence of the bound states can be found when the neutral particle is confined to a one-dimensional quantum ring and a quantum dot, and we also calculate the persistent currents in each case.
Kondo effect in transport through Aharonov-Bohm and Aharonov-Casher interferometers
NASA Astrophysics Data System (ADS)
Lobos, A. M.; Aligia, A. A.
2009-10-01
We derive the extension of the Hubbard model to include Rashba spin-orbit coupling that correctly describes Aharonov-Bohm and Aharonov-Casher phases in a ring under applied magnetic and electric fields. When the ring is connected to conducting leads, we develop a formalism that is able to describe both, Kondo and interference effects. We find that in the Kondo regime, the spin-orbit coupling reduces strongly the conductance from the unitary limit. This effect in combination with the magnetic flux, can be used to produce spin polarized carriers.
Yuan, Luqi; Xu, Shanshan; Fan, Shanhui
2015-11-15
We show that nonreciprocal unidirectional single-photon quantum transport can be achieved with the photonic Aharonov-Bohm effect. The system consists of a 1D waveguide coupling to two three-level atoms of the V-type. The two atoms, in addition, are each driven by an external coherent field. We show that the phase of the external coherent field provides a gauge potential for the photon states. With a proper choice of the phase difference between the two coherent fields, the transport of a single photon can exhibit unity contrast in its transmissions for the two propagation directions.
Scattering of spin-polarized electron in an Aharonov-Bohm potential
Khalilov, V.R.; Ho, C.-L.
2008-05-15
The scattering of spin-polarized electrons in an Aharonov-Bohm vector potential is considered. We solve the Pauli equation in 3 + 1 dimensions taking into account explicitly the interaction between the three-dimensional spin magnetic moment of electron and magnetic field. Expressions for the scattering amplitude and the cross section are obtained for spin-polarized electron scattered off a flux tube of small radius. It is also shown that bound electron states cannot occur in this quantum system. The scattering problem for the model of a flux tube of zero radius in the Born approximation is briefly discussed.
Evidence for dark excitons in a single carbon nanotube due to the Aharonov-Bohm effect.
Matsunaga, Ryusuke; Matsuda, Kazunari; Kanemitsu, Yoshihiko
2008-10-03
We studied exciton structures and the Aharonov-Bohm effect in a single carbon nanotube using micro-photoluminescence (PL) spectroscopy under a magnetic field at low temperatures. A single sharp PL peak from the bright exciton state of a single carbon nanotube was observed under zero magnetic field, and the additional PL of dark exciton state appeared below the bright exciton peak under high magnetic fields. It was found that the split between the bright and dark exciton states is several millielectron volts at zero field. The tube diameter dependence of the splitting arises from the intervalley short-range Coulomb interaction.
Anyonic Strings and Membranes in Anti-de Sitter Space and Dual Aharonov-Bohm Effects
Hartnoll, Sean A.
2007-03-16
It is observed that strings in AdS{sub 5}xS{sup 5} and membranes in AdS{sub 7}xS{sup 4} exhibit long range phase interactions. Two well separated membranes dragged around one another in anti-de Sitter space (AdS) acquire phases of 2{pi}/N. The same phases are acquired by a well separated F and D string dragged around one another. The phases are shown to correspond to both the standard and a novel type of Aharonov-Bohm effect in the dual field theory.
Tunable pseudogap Kondo effect and quantum phase transitions in Aharonov-Bohm interferometers.
Dias da Silva, Luis G G V; Sandler, Nancy; Simon, Pascal; Ingersent, Kevin; Ulloa, Sergio E
2009-04-24
We study two quantum dots embedded in the arms of an Aharonov-Bohm ring threaded by a magnetic flux. This system can be described by an effective one-impurity Anderson model with an energy- and flux-dependent density of states. For specific values of the flux, this density of states vanishes at the Fermi energy, yielding a controlled realization of the pseudogap Kondo effect. The conductance and transmission phase shifts reflect a nontrivial interplay between wave interference and interactions, providing clear signatures of quantum phase transitions between Kondo and non-Kondo ground states.
Force-free gravitational redshift: proposed gravitational Aharonov-Bohm experiment.
Hohensee, Michael A; Estey, Brian; Hamilton, Paul; Zeilinger, Anton; Müller, Holger
2012-06-08
We propose a feasible laboratory interferometry experiment with matter waves in a gravitational potential caused by a pair of artificial field-generating masses. It will demonstrate that the presence of these masses (and, for moving atoms, time dilation) induces a phase shift, even if it does not cause any classical force. The phase shift is identical to that produced by the gravitational redshift (or time dilation) of clocks ticking at the atom's Compton frequency. In analogy to the Aharonov-Bohm effect in electromagnetism, the quantum mechanical phase is a function of the gravitational potential and not the classical forces.
Coherent control of interacting particles using dynamical and Aharonov-Bohm phases.
Creffield, C E; Platero, G
2010-08-20
A powerful method of manipulating the dynamics of quantum coherent particles is to control the phase of their tunneling. We consider a system of two electrons hopping on a quasi-one-dimensional lattice in the presence of a uniform magnetic field and study the effect of adding a time-periodic driving potential. We show that the dynamical phases produced by the driving can combine with the Aharonov-Bohm phases to give precise control of the localization and dynamics of the particles, even in the presence of strong particle interactions.
Tunable Pseudogap Kondo Effect and Quantum Phase Transitions in Aharonov-Bohm Interferometers
Dias Da Silva, Luis G; Sandler, Nancy; Simon, Pascal; Ingersent, Kevin; Ulloa, Sergio E
2009-01-01
We study two quantum dots embedded in the arms of an Aharonov-Bohm ring threaded by a magnetic flux. This system can be described by an effective one-impurity Anderson model with an energy- and flux- dependent density of states. For specific values of the flux, this density of states vanishes at the Fermi energy, yielding a controlled realization of the pseudogap Kondo effect. The conductance and trans- mission phase shifts reflect a nontrivial interplay between wave interference and interactions, providing clear signatures of quantum phase transitions between Kondo and non-Kondo ground states.
Magnetically tunable Kondo-Aharonov-Bohm effect in a triangular quantum dot.
Kuzmenko, T; Kikoin, K; Avishai, Y
2006-02-03
The role of discrete orbital symmetry in mesoscopic physics is manifested in a system consisting of three identical quantum dots forming an equilateral triangle. Under a perpendicular magnetic field, this system demonstrates a unique combination of Kondo and Aharonov-Bohm features due to an interplay between continuous [spin-rotation SU(2)] and discrete (permutation C3v) symmetries, as well as U(1) gauge invariance. The conductance as a function of magnetic flux displays sharp enhancement or complete suppression depending on contact setups.
Two-particle nonlocal Aharonov-Bohm effect from two single-particle emitters.
Splettstoesser, Janine; Moskalets, Michael; Büttiker, Markus
2009-08-14
We propose a mesoscopic circuit in the quantum Hall effect regime comprising two uncorrelated single-particle sources and two distant Mach-Zehnder interferometers with magnetic fluxes, which allows us in a controllable way to produce orbitally entangled electrons. Two-particle correlations appear as a consequence of erasing of which-path information due to collisions taking place at distant interferometers and in general at different times. The two-particle correlations manifest themselves as an Aharonov-Bohm effect in noise, while the current is insensitive to magnetic fluxes. In an appropriate time interval the concurrence reaches a maximum and a Bell inequality is violated.
Nonreciprocal diffraction of light based on double-transition-assisted photonic Aharonov-Bohm effect
NASA Astrophysics Data System (ADS)
Yang, Fan; Li, Yanfeng
2016-10-01
We propose a nonreciprocal diffraction system based on the photonic Aharonov-Bohm effect. The implementation utilizes the simultaneous up and down photonic transition of Bloch modes in a dielectric grating created by time-harmonic dielectric constant modulation. This double transition process generates opposite effective magnetic fluxes for photons in symmetric and antisymmetric modes, which gives rise to nonreciprocal spatial interference between them. With the broken time-reversal symmetry, this system is possible to exhibit unidirectional highly efficient diffraction, which enables grating-based nonmagnetic isolation and circulation of free space light, and integrates the functions of gratings and isolators.
Anyonic strings and membranes in anti-de Sitter space and dual Aharonov-Bohm effects.
Hartnoll, Sean A
2007-03-16
It is observed that strings in AdS(5) x S(5) and membranes in AdS(7) x S(4) exhibit long range phase interactions. Two well separated membranes dragged around one another in anti-de Sitter space (AdS) acquire phases of 2 pi/N. The same phases are acquired by a well separated F and D string dragged around one another. The phases are shown to correspond to both the standard and a novel type of Aharonov-Bohm effect in the dual field theory.
Entin-Wohlman, O; Imry, Y; Aharony, A
2003-07-25
We consider an Aharonov-Bohm interferometer, connected to two electronic reservoirs, with a quantum dot embedded on one of its arms. We find a general expression for the persistent current at steady state, valid for the case where the electronic system is free of interactions except on the dot. The result is used to derive the modification in the persistent current brought about by coupling the quantum dot to a phonon source. The magnitude of the persistent current is found to be enhanced in an appropriate range of the intensity of the acoustic source.
The optical Aharonov-Bohm effect and magneto-optical properties in type-II quantum dots
NASA Astrophysics Data System (ADS)
Whiteside, Vincent Ryan
We present a detailed experimental study of the magneto-optical properties of type-II quantum dots (QDs) in: (1) ZnTe/ZnSe superlattices grown by Molecular Beam Epitaxy (MBE)---these Zn(SeTe) QDs evolve from Te-clustering in the ZnSe matrix during growth; and (2) diluted magnetic semiconductor, (ZnMn)Se, QDs in a ZnSe matrix produced by migration enhanced epitaxy. In case (1) the Zn(SeTe) QDs display large and robust (with temperature) oscillations as a function of magnetic field in both the photoluminescence energy and intensity as a result of the optical Aharonov-Bohm effect. The large strength of these oscillations is attributed to a combination of the type-II symmetry and the columnar geometry of the structures; the oscillations persist until 180K. The type-II diluted magnetic semiconductor, (ZnMn)Te quantum dots display similar oscillatory effects in the emission intensity. Interestingly, the coherence of the Aharonov-Bohm phase in these magnetic dots is strongly related to the spin polarization of the system due to the Mn-exciton exchange interaction as shown by the disappearance of the oscillations at low magnetic fields. The enhanced coherence at high fields, which leads to strong oscillations in intensity, is attributed to removal of magnetic disorder by the applied magnetic field. While the magnetic nature of the QDs is clear from the polarization measurements there is the seemingly contradictory behavior of a very small Zeeman shift for material that has a corresponding large Zeeman shift for the comparable composition of bulk (ZnMn)Te. More importantly, a red shift greater than 30 meV is observed in the peak energy of the PL as function of time after excitation with a picosecond pulse. These results can be explained by postulating formation of bound magnetic polarons in the QDs. The overall red shift is identified as the magnetic polaron binding energy, EMP; it is roughly independent of temperature, persisting up to 150K. The large MP binding energy is
Spin filtering in a Rashba-Dresselhaus-Aharonov-Bohm double-dot interferometer
NASA Astrophysics Data System (ADS)
Matityahu, Shlomi; Aharony, Amnon; Entin-Wohlman, Ora; Tarucha, Seigo
2013-12-01
We study the spin-dependent transport of spin-1/2 electrons through an interferometer made of two elongated quantum dots or quantum nanowires, which are subject to both an Aharonov-Bohm flux and (Rashba and Dresselhaus) spin-orbit interactions. Similar to the diamond interferometer proposed in our previous papers (Aharony et al 2011 Phys. Rev. B 84 035323; Matityahu et al 2013 Phys. Rev. B 87 205438), we show that the double-dot interferometer can serve as a perfect spin filter due to a spin interference effect. By appropriately tuning the external electric and magnetic fields which determine the Aharonov-Casher and Aharonov-Bohm phases, and with some relations between the various hopping amplitudes and site energies, the interferometer blocks electrons with a specific spin polarization, independent of their energy. The blocked polarization and the polarization of the outgoing electrons is controlled solely by the external electric and magnetic fields and do not depend on the energy of the electrons. Furthermore, the spin filtering conditions become simpler in the linear-response regime, in which the electrons have a fixed energy. Unlike the diamond interferometer, spin filtering in the double-dot interferometer does not require high symmetry between the hopping amplitudes and site energies of the two branches of the interferometer and thus may be more appealing from an experimental point of view.
Enhanced spin figure of merit in an Aharonov-Bohm ring with a double quantum dot
Zhou, Xingfei; Qi, Fenghua; Jin, Guojun
2014-04-21
We theoretically investigate the thermoelectric effects in an Aharonov-Bohm ring with a serially coupled double quantum dot embedded in one arm. An external magnetic field is perpendicularly applied to the two dots. Using the nonequilibrium Green's function method in the linear-response regime, we calculate the charge and spin figures of merit. When the energy levels of the two quantum dots are equal and the system is connected to two normal leads, a large spin figure of merit (Z{sub s}T ≈ 4.5) accompanying with a small charge figure of merit (Z{sub c}T ≈ 0) can be generated due to the remarkable bipolar effect. Further, when the system is connected to two ferromagnetic leads, the spin figure of merit can reach even a higher value about 9. Afterwards, we find that Z{sub s}T is enhanced while Z{sub c}T is reduced in the coaction of the Aharonov-Bohm flux and Rashba spin-orbit coupling. It is argued that the bipolar effect is positive (negative) to spin (charge) figure of merit in the presence of level detuning of the two quantum dots and intradot Coulomb interactions, respectively. Also, we propose a possible experiment to verify our results.
Aharonov-Bohm order parameters for non-Abelian gauge theories
Lo, H.
1995-12-15
The Aharonov-Bohm effect has been invoked to probe the phase structure of a gauge theory. Yet in the case of non-Abelian gauge theories, it proves difficult to formulate a general procedure that unambiguously specifies the realization of the gauge symmetry, e.g., the unbroken subgroup. In this paper we propose a set of order parameters that will do the job. We articulate the fact that any useful Aharonov-Bohm experiment necessarily proceeds in two stages: calibration and measurement. World sheets of virtual cosmic string loops can wrap around test charges, thus changing their states relative to other charges in the universe. Consequently, repeated flux measurements with test charges will not necessarily agree. This was the main stumbling block to previous attempts to construct order parameters for non-Abelian gauge theories. In those works, the particles that one uses for calibration and subsequent measurement are stored in {ital separate} ``boxes.`` By storing all test particles in the {ital same} ``box`` we show how quantum fluctuations can be overcome. The importance of gauge fixing is also emphasized. {copyright} 1995 The American Physical Society.
Eskin, G.
2008-02-15
We consider the inverse boundary value problem for the Schroedinger operator with time-dependent electromagnetic potentials in domains with obstacles. We extend the resuls of the author's works [Inverse Probl. 19, 49 (2003); 19, 985 (2003); 20, 1497 (2004)] to the case of time-dependent potentials. We relate our results to the Aharonov-Bohm effect caused by magnetic and electric fluxes.
Electron matter optics of the Aharonov-Bohm and Stern-Gerlach effects
NASA Astrophysics Data System (ADS)
McGregor, Scot Cameron
Since the advent of quantum mechanics and the idea that massive particles exhibit wave properties, physicists have made efforts to make use of the short deBroglie wave length of matter waves for fundamental as well as practical studies. Among these are the precise measurements allowed by interference, diffraction, and microscopy as well as the study of more fundamental aspects of quantum theory such as the Aharonov-Bohm effects or the Stern-Gerlach effect, which are described below. However, in order to use matter waves to observe any of these effects it is necessary to produce and maintain coherence in the waves which are used for measurement. With a grasp of what coherence is and how it may be achieved and maintained one can move forward to study the interesting phenomena associated with coherent matter waves. More specifically in this work the interference and diffraction of electron matter waves are considered. The phenomena under consideration are those associated with the interaction of the electric charge and magnetic dipole moment of the electron with external fields and potentials while in the process of interfering or diffracting. Namely the focus of this dissertation is the Aharonov-Bohm effect, the Aharonov-Casher effect, and the Stern-Gerlach effect. Additionally, a wide-angle electron beam-splitter capable of producing two centimeter beam separation at the detection plane is discussed. The beam-splitter utilizes a nanofabricated periodic grating in combination with a bi-prism element. Contrary to devices utilizing only bi-prism elements, the use of the periodic grating causes amplitude, and not wave front, splitting. Even at maximum separation, beam profiles remain undistorted, providing evidence that coherence is intact. This is a step towards the realization of a large area electron interferometer using such a grating bi-prism combination. Such an interferometer could, in principle, be used to test the dispersionless nature of the Aharonov-Bohm
Aharonov-Bohm Effect and High-Velocity Estimates of Solutions to the Schrödinger Equation
NASA Astrophysics Data System (ADS)
Ballesteros, Miguel; Weder, Ricardo
2011-04-01
The Aharonov-Bohm effect is a fundamental issue in physics that has been extensively studied in the literature and is discussed in most of the textbooks in quantum mechanics. The issues at stake are what are the fundamental electromagnetic quantities in quantum physics, if magnetic fields can act at a distance on charged particles and if the magnetic potentials have a real physical significance. The Aharonov-Bohm effect is a very controversial issue. From the experimental side the issues were settled by the remarkable experiments of Tonomura et al. (Phys Rev Lett 48:1443-1446, 1982; Phys Rev Lett 56:792-795, 1986) with toroidal magnets that gave a strong experimental evidence of the physical existence of the Aharonov-Bohm effect, and by the recent experiment of Caprez et al. (Phys Rev Lett 99:210401, 2007) that shows that the results of the Tonomura et al. experiments can not be explained by the action of a force. Aharonov and Bohm (Phys Rev 115:485-491, 1959) proposed an Ansatz for the solution to the Schrödinger equation in simply connected regions of space where there are no electromagnetic fields. It consists of multiplying the free evolution by the Dirac magnetic factor. The Aharonov-Bohm Ansatz predicts the results of the experiments of Tonomura et al. and of Caprez et al. Recently in Ballesteros and Weder (Math Phys 50:122108, 2009) we gave the first rigorous proof that the Aharonov-Bohm Ansatz is a good approximation to the exact solution for toroidal magnets under the conditions of the experiments of Tonomura et al. We provided a rigorous, simple, quantitative, error bound for the difference in norm between the exact solution and the Aharonov-Bohm Ansatz. In this paper we prove that these results do not depend on the particular geometry of the magnets and on the velocities of the incoming electrons used on the experiments, and on the gaussian shape of the wave packets used to obtain our quantitative error bound. We consider a general class of magnets that
Wave-packet rectification in nonlinear electronic systems: A tunable Aharonov-Bohm diode
NASA Astrophysics Data System (ADS)
Li, Yunyun; Zhou, Jun; Marchesoni, Fabio; Li, Baowen
2014-04-01
Rectification of electron wave-packets propagating along a quasi-one dimensional chain is commonly achieved via the simultaneous action of nonlinearity and longitudinal asymmetry, both confined to a limited portion of the chain termed wave diode. However, it is conceivable that, in the presence of an external magnetic field, spatial asymmetry perpendicular to the direction of propagation suffices to ensure rectification. This is the case of a nonlinear ring-shaped lattice with different upper and lower halves (diode), which is attached to two elastic chains (leads). The resulting device is mirror symmetric with respect to the ring vertical axis, but mirror asymmetric with respect to the chain direction. Wave propagation along the two diode paths can be modeled for simplicity by a discrete Schrödinger equation with cubic nonlinearities. Numerical simulations demonstrate that, thanks to the Aharonov-Bohm effect, such a diode can be operated by tuning the magnetic flux across the ring.
The heat kernel for two Aharonov-Bohm solenoids in a uniform magnetic field
NASA Astrophysics Data System (ADS)
Šťovíček, Pavel
2017-01-01
A non-relativistic quantum model is considered with a point particle carrying a charge e and moving in the plane pierced by two infinitesimally thin Aharonov-Bohm solenoids and subjected to a perpendicular uniform magnetic field of magnitude B. Relying on a technique originally due to Schulman, Laidlaw and DeWitt which is applicable to Schrödinger operators on multiply connected configuration manifolds a formula is derived for the corresponding heat kernel. As an application of the heat kernel formula, approximate asymptotic expressions are derived for the lowest eigenvalue lying above the first Landau level and for the corresponding eigenfunction while assuming that | eB | R2 /(ħ c) is large, where R is the distance between the two solenoids.
Interplay of Aharonov-Bohm and Berry phases in gate-defined graphene quantum dots
NASA Astrophysics Data System (ADS)
Heinl, Julia; Schneider, Martin; Brouwer, Piet W.
2013-06-01
We study the influence of a magnetic flux tube on the possibility to electrostatically confine electrons in a graphene quantum dot. Without a magnetic flux tube, the graphene pseudospin is responsible for a quantization of the total angular momentum to half-integer values. On the other hand, with a flux tube containing half a flux quantum, the Aharonov-Bohm phase and Berry phase precisely cancel, and we find a state at zero angular momentum that cannot be confined electrostatically. In this case, true bound states only exist in regular geometries for which states without zero-angular-momentum component exist, while nonintegrable geometries lack confinement. We support these arguments with a calculation of the two-terminal conductance of a gate-defined graphene quantum dot, which shows resonances for a disk-shaped geometry and for a stadium-shaped geometry without flux tube, but no resonances for a stadium-shaped quantum dot with a π-flux tube.
Scars in Dirac fermion systems: the influence of an Aharonov-Bohm flux
NASA Astrophysics Data System (ADS)
Wang, Cheng-Zhen; Huang, Liang; Chang, Kai
2017-01-01
Time-reversal ({ T }-) symmetry is fundamental to many physical processes. Typically, { T }-breaking for microscopic processes requires the presence of magnetic field. However, for 2D massless Dirac billiards, { T }-symmetry is broken automatically by the mass confinement, leading to chiral quantum scars. In this paper, we investigate the mechanism of { T }-breaking by analyzing the local current of the scarring eigenstates and their magnetic response to an Aharonov-Bohm flux. Our results unveil the complete understanding of the subtle { T }-breaking phenomena from both the semiclassical formula of chiral scars and the microscopic current and spin reflection at the boundaries, leading to a controlling scheme to change the chirality of the relativistic quantum scars. Our findings not only have significant implications on the transport behavior and spin textures of the relativistic pseudoparticles, but also add basic knowledge to relativistic quantum chaos.
Characterisation of ferromagnetic rings for Zernike phase plates using the Aharonov-Bohm effect.
Edgcombe, C J; Ionescu, A; Loudon, J C; Blackburn, A M; Kurebayashi, H; Barnes, C H W
2012-09-01
Holographic measurements on magnetised thin-film cobalt rings have demonstrated both onion and vortex states of magnetisation. For a ring in the vortex state, the difference between phases of electron paths that pass through the ring and those that travel outside it was found to agree very well with Aharonov-Bohm theory within measurement error. Thus the magnetic flux in thin-film rings of ferromagnetic material can provide the phase shift required for phase plates in transmission electron microscopy. When a ring of this type is used as a phase plate, scattered electrons will be intercepted over a radial range similar to the ring width. A cobalt ring of thickness 20 nm can produce a phase difference of π/2 from a width of just under 30 nm, suggesting that the range of radial interception for this type of phase plate can be correspondingly small.
On solutions of Coulomb system and its generalization to the Aharonov-Bohm effect
Lin, D.-H.
2009-02-15
The paper numerically analyzes the Aharonov-Bohm effect of an infinitely thin magnetic flux for its influence on a two- or three-dimensional (3d) solutions of Coulomb system in momentum and coordinate spaces. For any definitive eigenstate, it is shown that the flux shifts the position of the most probable radius (MPR) of a probability distribution inward or outward in momentum or coordinate spaces, respectively. Moreover, the probability density of the shifted MPR is amplified in the momentum space, while reduced in the coordinate space. Since the Coulomb force among charged particles dominate the structure of matter, shifting of the MPR controlling by the flux effect may be beneficial to the construction of nanostructure by manipulating the atomic and molecular bonds.
Thermoelectric effect in an Aharonov-Bohm ring with an embedded quantum dot.
Zheng, Jun; Chi, Feng; Lu, Xiao-Dong; Zhang, Kai-Cheng
2012-02-28
Thermoelectric effect is studied in an Aharonov-Bohm interferometer with an embedded quantum dot (QD) in the Coulomb blockade regime. The electrical conductance, electron thermal conductance, thermopower, and thermoelectric figure-of-merit are calculated by using the Keldysh Green's function method. It is found that the figure-of-merit ZT of the QD ring may be quite high due to the Fano effect originated from the quantum interference effect. Moreover, the thermoelectric efficiency is sensitive to the magnitude of the dot-lead and inter-lead coupling strengthes. The effect of intradot Coulomb repulsion on ZT is significant in the weak-coupling regime, and then large ZT values can be obtained at rather high temperature.
Goldhaber, Alfred Scharff; Requist, Ryan
2003-07-01
As a consequence of the Aharonov-Bohm effect, there is a quantum-induced attraction between a charged particle and a rigid, impenetrable hoop made from an arbitrarily thin tube containing a superconductor quantum of magnetic flux. This is remarkable because in classical physics there is no force between the two objects, and quantum-mechanical effects (associated with uncertainty-principle energy) generally are repulsive rather than attractive. For an incident spinless charged particle in a P wave (in a configuration with total angular momentum zero) we verify a resonance just above threshold using the Kohn variational principle in its S-matrix form. Even if optimistic choices of parameters describing a model system with these properties were feasible, the temperature required to observe the resonance would be far lower than has yet been attained in the laboratory.
Ying, Yibo; Jin, Guojun; Ma, Yu-Qiang
2009-07-08
We propose an Aharonov-Bohm interferometer with a quantum dot molecule embedded in one arm and study the spin-dependent transport due to the interplay of the Fano and Rashba effects. It is found that the Fano resonances of the molecular states exhibit opposite directions of asymmetric tails with one being from peak to dip and the other from dip to peak. The Rashba spin-orbit interaction induces a spin-dependent phase, making the two Fano dips overlap for one spin component of conductance and the two Fano peaks overlap for the other spin component. Both the direction and magnitude of the spin polarization of the conductance are easily controlled and manipulated through the Rashba parameter and interdot coupling strength. In addition, spin accumulations with opposite signs can be generated in the two quantum dots.
Aharonov-Bohm scattering of relativistic Dirac particles with an anomalous magnetic moment
Lin Qionggui
2005-10-15
The Aharonov-Bohm scattering of relativistic spin-1/2 particles with an anomalous magnetic moment are studied. The scattering cross sections for unpolarized and polarized particles are obtained by solving the Dirac-Pauli equation. It is somewhat unexpected that the results are in general the same as those for particles without an anomalous magnetic moment. However, when the incident energy takes some special values, the cross section for polarized particles is dramatically changed. In these cases the helicity of scattered particles is not conserved. In particular, the helicity of particles scattered in the backward direction is all reversed. In the nonrelativistic limit, a very simple relation between the polarized directions of the incident and scattered particles is found, for both general and special incident energies. For particles without an anomalous magnetic moment this relation can be drawn from previous results but it appears to be unnoticed.
Goldhaber, Alfred S.
2003-01-09
As a consequence of the Aharonov-Bohm effect, there is a quantum-induced attraction between a charged particle and a rigid impenetrable hoop made from an arbitrarily thin tube containing a superconductor quantum of magnetic flux. This is remarkable because in classical physics there is no force between the two objects, and quantum-mechanical effects (associated with uncertainty-principle energy) generally are repulsive rather than attractive. For an incident spinless charged particle in a P wave, in a configuration with total angular momentum zero, we verify a resonance just above threshold using the Kohn variational principle in its S-matrix form. Even if optimistic choices of parameters describing a model system with these properties turned out to be feasible, the temperature required to observe the resonance would be far lower than has yet been attained in the laboratory.
Aharonov-Bohm effect in the tunnelling of a quantum rotor in a linear Paul trap.
Noguchi, Atsushi; Shikano, Yutaka; Toyoda, Kenji; Urabe, Shinji
2014-05-13
Quantum tunnelling is a common fundamental quantum mechanical phenomenon that originates from the wave-like characteristics of quantum particles. Although the quantum tunnelling effect was first observed 85 years ago, some questions regarding the dynamics of quantum tunnelling remain unresolved. Here we realize a quantum tunnelling system using two-dimensional ionic structures in a linear Paul trap. We demonstrate that the charged particles in this quantum tunnelling system are coupled to the vector potential of a magnetic field throughout the entire process, even during quantum tunnelling, as indicated by the manifestation of the Aharonov-Bohm effect in this system. The tunnelling rate of the structures periodically depends on the strength of the magnetic field, whose period is the same as the magnetic flux quantum φ0 through the rotor [(0.99 ± 0.07) × φ0].
Aharonov-Bohm scattering in Chern-Simons theory of scalar particles
Boz, M.; Fainberg, V.; Pak, N.K.
1996-03-15
The S-matrix operator for relativistic theory of charged scalar particles interacting via Chern-Simon field is constructed and is shown to be formally the same as S-matrix in relativistic scalar quantum electrodynamics in which the Feynman diagrams with external photon lines are not considered and the propagators of the Chern-Simons particles are substituted in place of the ones for photons. All the one-loop Feynman diagrams for relativistic scattering amplitude of two charged particles are calculated. Due to the renormalizabilty of the theory only two diagrams have linear divergence, which are regularized. The nonrelativistic limit of the scattering amplitude is also finite, unlike the non-relativistic Chern-Simons scattering theory. It is found that for a certain value of the contact interaction, corresponding to the repulsive case, the scattering amplitude coincides with that of Aharonov-Bohm scattering, in the same approximation. 20 refs., 2 fig.
Wave-packet rectification in nonlinear electronic systems: a tunable Aharonov-Bohm diode.
Li, Yunyun; Zhou, Jun; Marchesoni, Fabio; Li, Baowen
2014-04-02
Rectification of electron wave-packets propagating along a quasi-one dimensional chain is commonly achieved via the simultaneous action of nonlinearity and longitudinal asymmetry, both confined to a limited portion of the chain termed wave diode. However, it is conceivable that, in the presence of an external magnetic field, spatial asymmetry perpendicular to the direction of propagation suffices to ensure rectification. This is the case of a nonlinear ring-shaped lattice with different upper and lower halves (diode), which is attached to two elastic chains (leads). The resulting device is mirror symmetric with respect to the ring vertical axis, but mirror asymmetric with respect to the chain direction. Wave propagation along the two diode paths can be modeled for simplicity by a discrete Schrödinger equation with cubic nonlinearities. Numerical simulations demonstrate that, thanks to the Aharonov-Bohm effect, such a diode can be operated by tuning the magnetic flux across the ring.
Transmission through a quantum dot molecule embedded in an Aharonov-Bohm interferometer.
Lovey, Daniel A; Gomez, Sergio S; Romero, Rodolfo H
2011-10-26
We study theoretically the transmission through a quantum dot molecule embedded in the arms of an Aharonov-Bohm four quantum dot ring threaded by a magnetic flux. The tunable molecular coupling provides a transmission pathway between the interferometer arms in addition to those along the arms. From a decomposition of the transmission in terms of contributions from paths, we show that antiresonances in the transmission arise from the interference of the self-energy along different paths and that application of a magnetic flux can produce the suppression of such antiresonances. The occurrence of a period of twice the quantum of flux arises at the opening of the transmission pathway through the dot molecule. Two different connections of the device to the leads are considered and their spectra of conductance are compared as a function of the tunable parameters of the model.
Topological phases reviewed: The Aharonov Bohm, Aharonov Casher, and He McKellar Wilkens phases
McKellar, B. H. J.; He, X-G.; Klein, A. G.
2014-03-05
There are three topological phases related to electromagnetic interactions in quantum mechanics: 1. The Aharonov Bohm phase acquired when a charged particle encircles a magnetic field but travels through a field free region. 2. The Aharonov Casher phase acquired when a magnetic dipole encircles electric charges but travels through a charge free region. 3. The He McKellar Wilkens phase acquired when an electric dipole encircles magnetic charges but travels through a charge free region. We review the conditions under which these phases are indeed topological and their experimental realisation. Because the He McKellar Wilkens phase has been recently observed we pay particular attention to how the basic concept of 'an electric dipole encircles magnetic charges' was realised experimentally, and discuss possible future experimental realisations.
Levinson's theorem and higher degree traces for Aharonov-Bohm operators
Kellendonk, Johannes; Pankrashkin, Konstantin; Richard, Serge
2011-05-15
We study Levinson-type theorems for the family of Aharonov-Bohm models from different perspectives. The first one is purely analytical involving the explicit calculation of the wave-operators and allowing to determine precisely the various contributions to the left hand side of Levinson's theorem, namely, those due to the scattering operator, the terms at 0-energy and at energy +{infinity}. The second one is based on non-commutative topology revealing the topological nature of Levinson's theorem. We then include the parameters of the family into the topological description obtaining a new type of Levinson's theorem, a higher degree Levinson's theorem. In this context, the Chern number of a bundle defined by a family of projections on bound states is explicitly computed and related to the result of a 3-trace applied on the scattering part of the model.
High-sensitivity rotation sensing with atom interferometers using Aharonov-Bohm effect
NASA Astrophysics Data System (ADS)
Özcan, Meriac
2006-02-01
In recent years there has been significant activity in research and development of high sensitivity accelerometers and gyroscopes using atom interferometers. In these devices, a fringe shift in the interference of atom de Broglie waves indicates the rotation rate of the interferometer relative to an inertial frame of reference. In both optical and atomic conventional Sagnac interferometers, the resultant phase difference due to rotation is independent of the wave velocity. However, we show that if an atom interforemeter is enclosed in a Faraday cage which is at some potential, the phase difference of the counter-propagating waves is proportional to the inverse square of the particle velocity and it is proportional to the applied potential. This is due to Aharonov-Bohm effect and it can be used to increase the rotation sensitivity of atom interferometers.
Electromagnetism, Local Covariance, the Aharonov-Bohm Effect and Gauss' Law
NASA Astrophysics Data System (ADS)
Sanders, Ko; Dappiaggi, Claudio; Hack, Thomas-Paul
2014-06-01
We quantise the massless vector potential A of electromagnetism in the presence of a classical electromagnetic (background) current, j, in a generally covariant way on arbitrary globally hyperbolic spacetimes M. By carefully following general principles and procedures we clarify a number of topological issues. First we combine the interpretation of A as a connection on a principal U(1)-bundle with the perspective of general covariance to deduce a physical gauge equivalence relation, which is intimately related to the Aharonov-Bohm effect. By Peierls' method we subsequently find a Poisson bracket on the space of local, affine observables of the theory. This Poisson bracket is in general degenerate, leading to a quantum theory with non-local behaviour. We show that this non-local behaviour can be fully explained in terms of Gauss' law. Thus our analysis establishes a relationship, via the Poisson bracket, between the Aharonov-Bohm effect and Gauss' law - a relationship which seems to have gone unnoticed so far. Furthermore, we find a formula for the space of electric monopole charges in terms of the topology of the underlying spacetime. Because it costs little extra effort, we emphasise the cohomological perspective and derive our results for general p-form fields A ( p < dim( M)), modulo exact fields, for the Lagrangian density . In conclusion we note that the theory is not locally covariant, in the sense of Brunetti-Fredenhagen-Verch. It is not possible to obtain such a theory by dividing out the centre of the algebras, nor is it physically desirable to do so. Instead we argue that electromagnetism forces us to weaken the axioms of the framework of local covariance, because the failure of locality is physically well-understood and should be accommodated.
Aharonov-Bohm physics with spin. II. Spin-flip effects in two-dimensional ballistic systems
NASA Astrophysics Data System (ADS)
Frustaglia, Diego; Hentschel, Martina; Richter, Klaus
2004-04-01
We study spin effects in the magnetoconductance of ballistic mesoscopic systems subject to inhomogeneous magnetic fields. We present a numerical approach to the spin-dependent Landauer conductance which generalizes recursive Green-function techniques to the case with spin. Based on this method we address spin-flip effects in quantum transport of spin-polarized and spin-unpolarized electrons through quantum wires and various two-dimensional Aharonov-Bohm geometries. In particular, we investigate the range of validity of a spin-switch mechanism recently found which allows for controlling spins indirectly via Aharonov-Bohm fluxes. Our numerical results are compared to a transfer-matrix model for one-dimensional ring structures presented in the first paper [Hentschel et al., Phys. Rev. B, preceding paper, Phys. Rev. B 69, 155326 (2004)] of this series.
Analytical expression of Kondo temperature in quantum dot embedded in Aharonov-Bohm ring
2011-01-01
We theoretically study the Kondo effect in a quantum dot embedded in an Aharonov-Bohm ring, using the "poor man's" scaling method. Analytical expressions of the Kondo temperature TK are given as a function of magnetic flux Φ penetrating the ring. In this Kondo problem, there are two characteristic lengths, Lc=ℏvF∕|ε˜0| and LK = ħvF = TK, where vF is the Fermi velocity and ε˜0 is the renormalized energy level in the quantum dot. The former is the screening length of the charge fluctuation and the latter is that of the spin fluctuation, i.e., size of Kondo screening cloud. We obtain diferent expressions of TK(Φ) for (i) Lc ≪ LK ≪ L, (ii) Lc ≪ L ≪ LK, and (iii) L ≪ Lc ≪ LK, where L is the size of the ring. TK is remarkably modulated by Φ in cases (ii) and (iii), whereas it hardly depends on Φ in case (i). PACS numbers: PMID:22112300
Aharonov-Bohm Effect and High-Momenta Inverse Scattering for the Klein-Gordon Equation
NASA Astrophysics Data System (ADS)
Ballesteros, Miguel; Weder, Ricardo
2016-10-01
We analyze spin-0 relativistic scattering of charged particles propagating in the exterior, $\\Lambda \\subset \\mathbb{R}^3$, of a compact obstacle $K \\subset \\mathbb{R}^3$. The connected components of the obstacle are handlebodies. The particles interact with an electro-magnetic field in $\\Lambda$ and an inaccessible magnetic field localized in the interior of the obstacle (through the Aharonov-Bohm effect). We obtain high-momenta estimates, with error bounds, for the scattering operator that we use to recover physical information: We give a reconstruction method for the electric potential and the exterior magnetic field and prove that, if the electric potential vanishes, circulations of the magnetic potential around handles (or equivalently, by Stokes' theorem, magnetic fluxes over transverse sections of handles) of the obstacle can be recovered, modulo $2 \\pi$. We additionally give a simple formula for the high-momenta limit of the scattering operator in terms of certain magnetic fluxes, in the absence of electric potential. If the electric potential does not vanish, the magnetic fluxes on the handles above referred can be only recovered modulo $\\pi$ and the simple expression of the high-momenta limit of the scattering operator does not hold true.
Transport properties of an Aharonov-Bohm ring with strong interdot Coulomb interaction.
Liu, Yu-Shen; Chen, Hao; Yang, Xi-Feng
2007-06-20
Based on the Keldysh Green's function technique and the equation-of-motion method, we investigate theoretically the electronic transport properties of an Aharonov-Bohm ring with embedded coupled double quantum dots connected to two electrodes in a symmetrical parallel configuration in the presence of strong interdot Coulomb interaction. Special attention is paid to the effects of the interdot Coulomb interaction on the transport properties. It has been shown numerically that the interdot Coulomb interaction gives rise to four electronic states in the ring. The quantum interferences between two strongly coupled electronic states and two weakly coupled ones lead to two Breit-Wigner and two Fano resonances in the linear conductance spectrum with the magnetic flux switched on or the imbalance between the energy levels of two quantum dots. The positions and shapes of the four resonances can be controlled by adjusting the magnetic flux through the device or energy levels of the two quantum dots. When the Fermi energy levels in the leads sweep across the weakly coupled electronic states, the negative differential conductance (NDC) is developed in the current-voltage characteristics for the non-equilibrium case.
Analytical expression of Kondo temperature in quantum dot embedded in Aharonov-Bohm ring.
Yoshii, Ryosuke; Eto, Mikio
2011-11-23
We theoretically study the Kondo effect in a quantum dot embedded in an Aharonov-Bohm ring, using the "poor man's" scaling method. Analytical expressions of the Kondo temperature TK are given as a function of magnetic flux Φ penetrating the ring. In this Kondo problem, there are two characteristic lengths, Lc=ℏvF∕|ε̃0| and LK = ħvF = TK, where vF is the Fermi velocity and ε̃0 is the renormalized energy level in the quantum dot. The former is the screening length of the charge fluctuation and the latter is that of the spin fluctuation, i.e., size of Kondo screening cloud. We obtain diferent expressions of TK(Φ) for (i) Lc ≪ LK ≪ L, (ii) Lc ≪ L ≪ LK, and (iii) L ≪ Lc ≪ LK, where L is the size of the ring. TK is remarkably modulated by Φ in cases (ii) and (iii), whereas it hardly depends on Φ in case (i).PACS numbers:
Cotaescu, I I; Papp, E
2007-06-20
This paper deals with the total persistent current at T = 0 produced by the exact energy solution of the Dirac electron moving on isolated 1D Aharonov-Bohm rings. Leading contributions concerning the non-relativistic limit are written down for large values of the electron number. Usual non-relativistic currents get reproduced, but now in terms of a reversed parity of the electron number. Such an 'anomaly' is able to serve as a signature of the Dirac electron referred to above.
Correa, Francisco Jakubsky, Vit Plyushchay, Mikhail S.
2009-05-15
We explain the origin and the nature of a special nonlinear supersymmetry of a reflectionless Poeschl-Teller system by the Aharonov-Bohm effect for a non-relativistic particle on the AdS{sub 2}. A key role in the supersymmetric structure appearing after reduction by a compact generator of the AdS{sub 2} isometry is shown to be played by the discrete symmetries related to the space and time reflections in the ambient Minkowski space. We also observe that a correspondence between the two quantum non-relativistic systems is somewhat of the AdS/CFT holography nature.
Two-Particle Nonlocal Aharonov-Bohm Effect from Two Single-Particle Emitters
NASA Astrophysics Data System (ADS)
Splettstoesser, Janine
2010-03-01
High-frequency single-particle emitters have been realized experimentally in the integer quantum Hall effect regime [1]: the particles are injected into edge states, operating as wave guides, and encounter splitters realized by quantum point contacts. These tools allow for the implementation of complex interferometers in mesoscopic systems showing two-particle interference effects. An example for tunable two-particle correlations is manifest in the electronic analogue of the Hong-Ou-Mandel interferometer [2], where a noise suppression is found due to the Pauli principle. In the work presented here we explore the entanglement production from two uncorrelated sources. We therefore propose a mesoscopic circuit in the quantum Hall effect regime comprising two independent single-particle sources and two distant Mach-Zehnder interferometers with magnetic fluxes. This and the tunability of the single-particle sources allow in a controllable way to produce orbitally entangled electrons [3]. Two-particle correlations appear as a consequence of erasing of which-path information due to collisions taking place at distant interferometers and in general at different times. While the current in this setup is insensitive to the magnetic flux, the two-particle correlations manifest themselves as an Aharonov-Bohm effect in the noise. In an appropriate time-interval the concurrence reaches a maximum and a Bell inequality is violated, proving the existence of time-bin entanglement.[4pt] [1] G. Fève, A. Mah'e, J.-M. Berroir, T. Kontos, B. Placais, D. C. Glattli, A. Cavanna, B. Etienne, and Y. Jin, Science 316, 1169 (2007).[0pt] [2] S. Ol'Khovskaya, J. Splettstoesser, M. Moskalets, and M. Buttiker, Phys. Rev. Lett. 101, 166802 (2008).[0pt] [3] J. Splettstoesser, M. Moskalets, and M. Buttiker, Phys. Rev. Lett.103, 076804 (2009).
High-Velocity Estimates for the Scattering Operator and Aharonov-Bohm Effect in Three Dimensions
NASA Astrophysics Data System (ADS)
Ballesteros, Miguel; Weder, Ricardo
2009-01-01
We obtain high-velocity estimates with error bounds for the scattering operator of the Schrödinger equation in three dimensions with electromagnetic potentials in the exterior of bounded obstacles that are handlebodies. A particular case is a finite number of tori. We prove our results with time-dependent methods. We consider high-velocity estimates where the direction of the velocity of the incoming electrons is kept fixed as its absolute value goes to infinity. In the case of one torus our results give a rigorous proof that quantum mechanics predicts the interference patterns observed in the fundamental experiments of Tonomura et al. that gave conclusive evidence of the existence of the Aharonov-Bohm effect using a toroidal magnet. We give a method for the reconstruction of the flux of the magnetic field over a cross-section of the torus modulo 2π. Equivalently, we determine modulo 2π the difference in phase for two electrons that travel to infinity, when one goes inside the hole and the other outside it. For this purpose we only need the high-velocity limit of the scattering operator for one direction of the velocity of the incoming electrons. When there are several tori-or more generally handlebodies-the information that we obtain in the fluxes, and on the difference of phases, depends on the relative position of the tori and on the direction of the velocities when we take the high-velocity limit of the incoming electrons. For some locations of the tori we can determine all the fluxes modulo 2π by taking the high-velocity limit in only one direction. We also give a method for the unique reconstruction of the electric potential and the magnetic field outside the handlebodies from the high-velocity limit of the scattering operator.
Quantum oscillations in superconductors in magnetic field
NASA Astrophysics Data System (ADS)
Gvozdikov, Vladimir M.; Gvozdikova, Mariya V.
2000-07-01
The Aharonov-Bohm oscillations (ABO) of the free energy, the critical temperature, and the magnetic susceptibility in a stack of hollow mesoscopic cylinders are calculated. It is shown that sinusoidal (in flux) ABO crosses over to the parabolic Little-Parks oscillations (LPO) when the diameter of cylinders exceeds the coherence length. The exponential temperature behaviour of the magnetic susceptibility is like that found in Ag cylinders with thin Nb coating [Czech. J. Physics 46 (1996) 2317]. The formal analogy between oscillations of the free energy in the Aharonov-Bohm system in question and the de Haas-van Alphen oscillations (dHvAO) in layered superconductors is discussed.
Induced vacuum charge of massless fermions in Coulomb and Aharonov-Bohm potentials in 2+1 dimensions
NASA Astrophysics Data System (ADS)
Mamsurov, I. V.; Khalilov, V. R.
2016-08-01
We study the vacuum polarization of zero-mass charged fermions in Coulomb and Aharonov-Bohm potentials in 2+1 dimensions. For this, we construct the Green's function of the two-dimensional Dirac equation in the considered field configuration and use it to find the density of the induced vacuum charge in so-called subcritical and supercritical regions. The Green's function is represented in regular and singular (in the source) solutions of the Dirac radial equation for a charged fermion in Coulomb and Aharonov-Bohm potentials in 2+1 dimensions and satisfies self-adjoint boundary conditions at the source. In the supercritical region, the Green's function has a discontinuity related to the presence of singularities on the nonphysical sheet of the complex plane of "energy," which are caused by the appearance of an infinite number of quasistationary states with negative energies. Ultimately, this situation represents the neutral vacuum instability. On the boundary of the supercritical region, the induced vacuum charge is independent of the self-adjoint extension. We hope that the obtained results will contribute to a better understanding of important problems in quantum electrodynamics and will also be applicable to the problem of screening the Coulomb impurity due to vacuum polarization in graphene with the effects associated with taking the electron spin into account.
NASA Astrophysics Data System (ADS)
Hod, Oded; Baer, Roi; Rabani, Eran
2008-09-01
Control of conductance in molecular junctions is of key importance in the growing field of molecular electronics. The current in these junctions is often controlled by an electric gate designed to shift conductance peaks into the low bias regime. Magnetic fields, on the other hand, have rarely been used due to the small magnetic flux captured by molecular conductors (an exception is the Kondo effect in single-molecule transistors). This is in contrast to a related field, electronic transport through mesoscopic devices, where considerable activity with magnetic fields has led to a rich description of transport. The scarcity of experimental activity is due to the belief that significant magnetic response is obtained only when the magnetic flux is of the order of the quantum flux, while attaining such a flux for molecular and nanoscale devices requires unrealistic magnetic fields. Here we review recent theoretical work regarding the essential physical requirements necessary for the construction of nanometer-scale magnetoresistance devices based on an Aharonov-Bohm molecular interferometer. We show that control of the conductance properties using small fractions of a magnetic flux can be achieved by carefully adjusting the lifetime of the conducting electrons through a pre-selected single state that is well separated from other states due to quantum confinement effects. Using a simple analytical model and more elaborate atomistic calculations we demonstrate that magnetic fields which give rise to a magnetic flux comparable to 10-3 of the quantum flux can be used to switch a class of different molecular and nanometer rings, ranging from quantum corrals, carbon nanotubes and even a molecular ring composed of polyconjugated aromatic materials. The unique characteristics of the magnetic field as a gate is further discussed and demonstrated in two different directions. First, a three-terminal molecular router devices that can function as a parallel logic gate, processing
Magnetoresistance of nanoscale molecular devices based on Aharonov-Bohm interferometry.
Hod, Oded; Baer, Roi; Rabani, Eran
2008-09-24
Control of conductance in molecular junctions is of key importance in the growing field of molecular electronics. The current in these junctions is often controlled by an electric gate designed to shift conductance peaks into the low bias regime. Magnetic fields, on the other hand, have rarely been used due to the small magnetic flux captured by molecular conductors (an exception is the Kondo effect in single-molecule transistors). This is in contrast to a related field, electronic transport through mesoscopic devices, where considerable activity with magnetic fields has led to a rich description of transport. The scarcity of experimental activity is due to the belief that significant magnetic response is obtained only when the magnetic flux is of the order of the quantum flux, while attaining such a flux for molecular and nanoscale devices requires unrealistic magnetic fields. Here we review recent theoretical work regarding the essential physical requirements necessary for the construction of nanometer-scale magnetoresistance devices based on an Aharonov-Bohm molecular interferometer. We show that control of the conductance properties using small fractions of a magnetic flux can be achieved by carefully adjusting the lifetime of the conducting electrons through a pre-selected single state that is well separated from other states due to quantum confinement effects. Using a simple analytical model and more elaborate atomistic calculations we demonstrate that magnetic fields which give rise to a magnetic flux comparable to 10(-3) of the quantum flux can be used to switch a class of different molecular and nanometer rings, ranging from quantum corrals, carbon nanotubes and even a molecular ring composed of polyconjugated aromatic materials. The unique characteristics of the magnetic field as a gate is further discussed and demonstrated in two different directions. First, a three-terminal molecular router devices that can function as a parallel logic gate, processing
NASA Astrophysics Data System (ADS)
Khatua, Pradip; Bansal, Bhavtosh; Shahar, Dan
2014-01-01
In a "thought experiment," now a classic in physics pedagogy, Feynman visualizes Young's double-slit interference experiment with electrons in magnetic field. He shows that the addition of an Aharonov-Bohm phase is equivalent to shifting the zero-field wave interference pattern by an angle expected from the Lorentz force calculation for classical particles. We have performed this experiment with one slit, instead of two, where ballistic electrons within two-dimensional electron gas diffract through a small orifice formed by a quantum point contact (QPC). As the QPC width is comparable to the electron wavelength, the observed intensity profile is further modulated by the transverse waveguide modes present at the injector QPC. Our experiments open the way to realizing diffraction-based ideas in mesoscopic physics.
Khatua, Pradip; Bansal, Bhavtosh; Shahar, Dan
2014-01-10
In a "thought experiment," now a classic in physics pedagogy, Feynman visualizes Young's double-slit interference experiment with electrons in magnetic field. He shows that the addition of an Aharonov-Bohm phase is equivalent to shifting the zero-field wave interference pattern by an angle expected from the Lorentz force calculation for classical particles. We have performed this experiment with one slit, instead of two, where ballistic electrons within two-dimensional electron gas diffract through a small orifice formed by a quantum point contact (QPC). As the QPC width is comparable to the electron wavelength, the observed intensity profile is further modulated by the transverse waveguide modes present at the injector QPC. Our experiments open the way to realizing diffraction-based ideas in mesoscopic physics.
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.
Smirnov, A. G.
2015-12-15
We develop a general technique for finding self-adjoint extensions of a symmetric operator that respects a given set of its symmetries. Problems of this type naturally arise when considering two- and three-dimensional Schrödinger operators with singular potentials. The approach is based on constructing a unitary transformation diagonalizing the symmetries and reducing the initial operator to the direct integral of a suitable family of partial operators. We prove that symmetry preserving self-adjoint extensions of the initial operator are in a one-to-one correspondence with measurable families of self-adjoint extensions of partial operators obtained by reduction. The general scheme is applied to the three-dimensional Aharonov-Bohm Hamiltonian describing the electron in the magnetic field of an infinitely thin solenoid. We construct all self-adjoint extensions of this Hamiltonian, invariant under translations along the solenoid and rotations around it, and explicitly find their eigenfunction expansions.
NASA Astrophysics Data System (ADS)
Liu, Bin; Li, Yunyun; Zhou, Jun; Nakayama, Tsuneyoshi; Li, Baowen
2016-06-01
We theoretically investigate the spin-dependent Seebeck effect in an Aharonov-Bohm mesoscopic ring in the presence of both Rashba and Dresselhaus spin-orbit interactions under magnetic flux perpendicular to the ring. We apply the Green's function method to calculate the spin Seebeck coefficient employing the tight-binding Hamiltonian. It is found that the spin Seebeck coefficient is proportional to the slope of the energy-dependent transmission coefficients. We study the strong dependence of spin Seebeck coefficient on the Fermi energy, magnetic flux, strength of spin-orbit coupling, and temperature. Maximum spin Seebeck coefficients can be obtained when the strengths of Rashba and Dresselhaus spin-orbit couplings are slightly different. The spin Seebeck coefficient can be reduced by increasing temperature and disorder.
Bulgakov, Evgeny N; Sadreev, Almas F
2016-07-06
We consider the trapping of electrons with a definite spin polarization by bound states in the continuum (BSC) in the open Aharonov-Bohm rings in the presence of the Rashba spin-orbit interaction (RSOI). Neglecting the Zeeman term we show the existence of BSCs in the one-dimensional ring when the eigenstates of the closed ring are doubly degenerate. With account of the Zeeman term BSCs occur only at the points of threefold degeneracy. The BSCs are found in the parametric space of flux and RSOI strength in close pairs with opposite spin polarization. Thereby the spin polarization of electrons transmitted through the ring can be altered by minor variation of magnetic or electric field at the vicinity of these pairs. Numerical simulations of the two-dimensional open ring show similar results for the BSCs. Encircling the BSC points in the parametric space of the flux and the RSOI constant gives rise to a geometric phase.
Wang, Xiaofei; Liu, Xiaojie; Zhao, Xueyang; Yin, Haitao; Wan, Weilong; Feng, Li
2014-03-01
The spin polarized transport properties through an Aharonov-Bohm ring embedded with a double quantum dot-molecule in each arm with Rashba spin-orbit (RSO) interaction is theoretically studied in the framework of the equation of motion of Green's function. Based on molecular state representation, the anti-resonance phenomenon in the conductance spectrum is readily explained. We found that the position of antiresonant peaks in conductance spectrum is determined by the interdot coupling strengths. Moreover, the magnitude of conductance of each spin component can be manipulated by the Rashba spin orbit interaction strength. Especially only one spin component electron can be allowed to transport through this structure by modulating the strength of RSO interaction properly.
NASA Astrophysics Data System (ADS)
Bulgakov, Evgeny N.; Sadreev, Almas F.
2016-07-01
We consider the trapping of electrons with a definite spin polarization by bound states in the continuum (BSC) in the open Aharonov-Bohm rings in the presence of the Rashba spin-orbit interaction (RSOI). Neglecting the Zeeman term we show the existence of BSCs in the one-dimensional ring when the eigenstates of the closed ring are doubly degenerate. With account of the Zeeman term BSCs occur only at the points of threefold degeneracy. The BSCs are found in the parametric space of flux and RSOI strength in close pairs with opposite spin polarization. Thereby the spin polarization of electrons transmitted through the ring can be altered by minor variation of magnetic or electric field at the vicinity of these pairs. Numerical simulations of the two-dimensional open ring show similar results for the BSCs. Encircling the BSC points in the parametric space of the flux and the RSOI constant gives rise to a geometric phase.
Hou, Dong; Wang, Shikuan; Wang, Rulin; Ye, LvZhou; Xu, RuiXue; Zheng, Xiao; Yan, YiJing
2015-03-14
Several recent advancements for the hierarchical equations of motion (HEOM) approach are reported. First, we propose an a priori estimate for the optimal number of basis functions for the reservoir memory decomposition. Second, we make use of the sparsity of auxiliary density operators (ADOs) and propose two ansatzs to screen out all the intrinsic zero ADO elements. Third, we propose a new truncation scheme by utilizing the time derivatives of higher-tier ADOs. These novel techniques greatly reduce the memory cost of the HEOM approach, and thus enhance its efficiency and applicability. The improved HEOM approach is applied to simulate the coherent dynamics of Aharonov-Bohm double quantum dot interferometers. Quantitatively accurate dynamics is obtained for both noninteracting and interacting quantum dots. The crucial role of the quantum phase for the magnitude of quantum coherence and quantum entanglement is revealed.
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.
Schütz, G; Rembold, A; Pooch, A; Prochel, H; Stibor, A
2015-11-01
We propose an experiment for the first proof of the type I electric Aharonov-Bohm effect in an ion interferometer for hydrogen. The performances of three different beam separation schemes are simulated and compared. The coherent ion beam is generated by a single atom tip (SAT) source and separated by either two biprisms with a quadrupole lens, two biprisms with an einzel-lens or three biprisms. The beam path separation is necessary to introduce two metal tubes that can be pulsed with different electric potentials. The high time resolution of a delay line detector allows to work with a continuous ion beam and circumvents the pulsed beam operation as originally suggested by Aharonov and Bohm. We demonstrate that the higher mass and therefore lower velocity of ions compared to electrons combined with the high expected SAT ion emission puts the direct proof of this quantum effect for the first time into reach of current technical possibilities. Thereby a high detection rate of coherent ions is crucial to avoid long integration times that allow the influence of dephasing noise from the environment. We can determine the period of the expected matter wave interference pattern and the signal on the detector by determining the superposition angle of the coherent partial beams. Our simulations were tested with an electron interferometer setup and agree with the experimental results. We determine the separation scheme with three biprisms to be most efficient and predict a total signal acquisition time of only 80s to measure a phase shift from 0 to 2π due to the electric Aharonov-Bohm effect.
Monisha, P. J.; Sankar, I. V.; Sil, Shreekantha; Chatterjee, Ashok
2016-01-01
Persistent current in a correlated quantum ring threaded by an Aharonov-Bohm flux is studied in the presence of electron-phonon interactions and Rashba spin-orbit coupling. The quantum ring is modeled by the Holstein-Hubbard-Rashba Hamiltonian and the energy is calculated by performing the conventional Lang-Firsov transformation followed by the diagonalization of the effective Hamiltonian within a mean-field approximation. The effects of Aharonov-Bohm flux, temperature, spin-orbit and electron-phonon interactions on the persistent current are investigated. It is shown that the electron-phonon interactions reduce the persistent current, while the Rashba coupling enhances it. It is also shown that temperature smoothens the persistent current curve. The effect of chemical potential on the persistent current is also studied. PMID:26831831
Monisha, P J; Sankar, I V; Sil, Shreekantha; Chatterjee, Ashok
2016-02-01
Persistent current in a correlated quantum ring threaded by an Aharonov-Bohm flux is studied in the presence of electron-phonon interactions and Rashba spin-orbit coupling. The quantum ring is modeled by the Holstein-Hubbard-Rashba Hamiltonian and the energy is calculated by performing the conventional Lang-Firsov transformation followed by the diagonalization of the effective Hamiltonian within a mean-field approximation. The effects of Aharonov-Bohm flux, temperature, spin-orbit and electron-phonon interactions on the persistent current are investigated. It is shown that the electron-phonon interactions reduce the persistent current, while the Rashba coupling enhances it. It is also shown that temperature smoothens the persistent current curve. The effect of chemical potential on the persistent current is also studied.
Numazaki, Kazuya; Imai, Hiromitsu; Morinaga, Atsuo
2010-03-15
The second-order Zeeman effect of the sodium clock transition in a weak magnetic field of less than 50 {mu}T was measured as the scalar Aharonov-Bohm phase by two-photon stimulated Raman atom interferometry. The ac Stark effect of the Raman pulse was canceled out by adopting an appropriate intensity ratio of two photons in the Raman pulse. The Ramsey fringes for the pulse separation of 7 ms were obtained with a phase uncertainty of {pi}/200 rad. The nondispersive feature of the scalar Aharonov-Bohm phase was clearly demonstrated through 18 fringes with constant amplitude. The Breit-Rabi formula of the sodium clock transition was verified to be {Delta}{nu}=(0.222{+-}0.003)x10{sup 12}xB{sup 1.998{+-}0.004} in a magnetic field of less than 50 {mu}T.
Half-period Aharonov-Bohm oscillations in disordered rotating optical ring cavities
NASA Astrophysics Data System (ADS)
Li, Huanan; Kottos, Tsampikos; Shapiro, Boris
2016-09-01
There exists an analogy between Maxwell equations in a rotating frame and the Schrödinger equation for a charged particle in the presence of a magnetic field. We exploit this analogy to point out that electromagnetic phenomena in the rotating frame, under appropriate conditions, can exhibit periodicity with respect to the angular velocity of rotation. In particular, in disordered ring cavities one finds the optical analog of the Al'tshuler-Aronov-Spivak effect well known in mesoscopic physics of disordered metals.
NASA Astrophysics Data System (ADS)
Ji, Haojie
In this thesis I develop understanding of the fundamental physical and material properties of type-II ZnTe/ZnSe submonolayer quantum dots (QDs), grown via combination of molecular beam epitaxy (MBE) and migration enhanced epitaxy (MEE). I use magneto-photoluminescence, including excitonic Aharonov-Bohm (AB) effect and polarized optical spectroscopy as the primary tools in this work. I present previous studies as well as the background of optical and magneto-optical processes in semiconductor nanostructures and introduce the experimental methods in Chapters 1 - 3. In Chapter 4 I focus on the excitonic AB effect in the type-II QDs. I develop a lateral tightly-bound exciton model for ZnTe/ZnSe type-II QDs, using analytical methods and numerical calculations. This explained the magneto-PL observation and allowed for establishing the size and density of the QDs in each sample based on the results of PL and magneto-PL measurements. For samples with larger QDs, I observe behaviors that fall between properties of quantum-dot and quantum-well-like systems due to increased QD densities and their type-II nature. Finally, the decoherence mechanisms of the AB excitons are investigated via the temperature dependent studies of the magneto-PL. It is determined that the AB exciton decoherence is due to transport-like (acoustic phonon) scattering of the electrons moving in the ZnSe barriers, but with substantially smaller magnitude of electron-phonon coupling constant due to relatively strong electron-hole coupling within these type-II QDs. In Chapter 5 I discuss the results of circularly polarized magneto-PL measurements. A model with ultra-long spin-flip time of holes confined to submonolayer QDs is proposed. The g-factor of type-II excitons was extracted from the Zeeman splitting and the g-factor of electrons was obtained by fitting the temperature dependence of the degree of circular polarization (DCP), from which g-factor of holes confined within ZnTe QDs was found. It is shown
NASA Astrophysics Data System (ADS)
Peng, Ju; Yu, Hua-Ling; Wang, Zhi-Guo
2009-12-01
This paper theoretically reports the nonlocal Andreev reflection and spin current in a normal metal-ferromagnetic metal-superconducting Aharonov-Bohm interferometer. It is found that the electronic current and spin current are sensitive to systematic parameters, such as the gate voltage of quantum dots and the external magnetic flux. The electronic current in the normal metal lead results from two competing processes: quasiparticle transmission and nonlocal Andreev reflection. The appearance of zero spin-up electronic current (or spin-down electronic current) signals the existence of nonlocal Andreev reflection, and the presence of zero electronic current results in the appearance of pure spin current.
Tokuno, Akiyuki; Oshikawa, Masaki; Demler, Eugene
2008-04-11
We study one-dimensional Bose liquids of interacting ultracold atoms in the Y-shaped potential when each branch is filled with atoms. We find that the excitation packet incident on a single Y junction should experience a negative density reflection analogous to the Andreev reflection at normal-superconductor interfaces, although the present system does not contain fermions. In a ring-interferometer-type configuration, we find that the transport is completely insensitive to the (effective) flux contained in the ring, in contrast with the Aharonov-Bohm effect of a single particle in the same geometry.
Tokuno, Akiyuki; Oshikawa, Masaki; Demler, Eugene
2008-04-11
We study one-dimensional Bose liquids of interacting ultracold atoms in the Y-shaped potential when each branch is filled with atoms. We find that the excitation packet incident on a single Y junction should experience a negative density reflection analogous to the Andreev reflection at normal-superconductor interfaces, although the present system does not contain fermions. In a ring-interferometer-type configuration, we find that the transport is completely insensitive to the (effective) flux contained in the ring, in contrast with the Aharonov-Bohm effect of a single particle in the same geometry.
Lin, D.-H.
2004-05-01
Partial wave theory of a three dimensional scattering problem for an arbitrary short range potential and a nonlocal Aharonov-Bohm magnetic flux is established. The scattering process of a 'hard sphere'-like potential and the magnetic flux is examined. An anomalous total cross section is revealed at the specific quantized magnetic flux at low energy which helps explain the composite fermion and boson model in the fractional quantum Hall effect. Since the nonlocal quantum interference of magnetic flux on the charged particles is universal, the nonlocal effect is expected to appear in a quite general potential system and will be useful in understanding some other phenomena in mesoscopic physics.
Miyamoto, Satoru; Ishikawa, Toyofumi; Eto, Mikio; Itoh, Kohei M.; Moutanabbir, Oussama; Haller, Eugene E.; Sawano, Kentarou; Shiraki, Yasuhiro
2010-08-15
We report on a magnetophotoluminescence study of isotopically pure {sup 70}Ge/Si self-assembled type-II quantum dots. Oscillatory behaviors attributed to the Aharonov-Bohm effect are simultaneously observed for the emission energy and intensity of excitons subject to an increasing magnetic field. When the magnetic flux penetrates through the ringlike trajectory of an electron moving around each quantum dot, the ground state of an exciton experiences a change in its angular momentum. Our results provide the experimental evidence for the phase coherence of localized electron wave functions in group-IV Ge/Si self-assembled quantum structures.
NASA Astrophysics Data System (ADS)
Amaresh Kumar, M. V.; Sahoo, Debendranath
A characterization of the two-terminal open-ring Aharonov-Bohm interferometer is made by analyzing the phase space plots in the complex transmission amplitude plane. Two types of plots are considered: type 1 plot uses the magnetic flux as the variable parameter and type 2 plot which uses the electron momentum as the variable parameter. In type 1 plot, the trajectory closes upon itself only when the ratio R of the arm lengths (of the interferometer) is a rational fraction, and the shape and the type of the generated flower-like pattern is sensitive to the electron momentum. For momenta corresponding to discrete eigenstates of the perfect ring (i.e., the ring without the leads), the trajectory passes through the origin a certain fixed number of times before closing upon itself, whereas for arbitrary momenta it never passes through the origin. Although the transmission coefficient is periodic in the flux with the elementary flux quantum as the basic period, the phenomenon of electron transmission is shown not to be so when analyzed via the present technique. The periodicity is seen to spread over several flux units whenever R is a rational fraction whereas there is absolutely no periodicity present when R is an irrational number. In type 2 plot, closed trajectories passing through the origin a number of times are seen for R being a rational fraction. The case R = 1 (i.e., a symmetric ring) with zero flux is rather pathological — it presents a closed loop surrounding the origin. For irrational R values, the trajectories never close.
Observing Altshuler--Aronov--Spivak Oscillation in a Hexagonal Antidot Array of Monolayer Graphene
NASA Astrophysics Data System (ADS)
Yagi, Ryuta; Shimomura, Midori; Tahara, Fumiya; Kobara, Hiroaki; Fukada, Seiya
2012-06-01
We show that hexagonal antidot lattices of monolayer graphene exhibited the Altshuler--Aronov--Spivak (AAS) effect in low field magnetoresistance. In higher magnetic fields, Aharonov--Bohm-type oscillations were visible. The phase of AAS oscillation indicated that the chirality effect of graphene is suppressed because of inter-valley scattering due to boundary scatterings.
NASA Astrophysics Data System (ADS)
Lillianfeld, R. B.; Kallaher, R. L.; Heremans, J. J.; van Roy, W.; Borghs, G.
2011-03-01
We investigate electron spin- and phase coherence in an array of quasi-ballistic InAs quantum well mesoscopic rings through observation of Aharonov-Bohm h/e oscillations (AB) and Altshuler-Aronov-Spivak h/2e oscillations (AAS). The temperature dependence of the AAS oscillations is characterized through a single effective coherence length, Leff , following the formalism of Douçot and Rammal, from which the phase coherence length, Lϕ and the spin coherence length as limited by spin-orbit interaction, LSO , are extracted. AB oscillations are also present, and can be separated from AAS by Fourier transformation. We contrast the AAS method of extracting the coherence lengths with analysis of the AB oscillation amplitudes. Previous studies have examined Lϕ from AB signals in single ballistic rings, or by using AAS amplitudes in large networks, or have observed AB and AAS in single rings with spin-orbit interaction. Here the presence of both AB and AAS in an array with spin-orbit interaction allows for study of both Lϕ and LSO , and enables direct juxtaposition of different quantum coherence phenomena as means for measuring coherence lengths (DOE DE-FG02-08ER46532).
2012-01-01
Using the nonequilibrium Green’s function method, we theoretically study the Andreev reflection(AR) in a four-terminal Aharonov-Bohm interferometer containing a coupled double quantum dot with the Rashba spin-orbit interaction (RSOI) and the coherent indirect coupling via two ferromagnetic leads. When two ferromagnetic electrodes are in the parallel configuration, the spin-up conductance is equal to the spin-down conductance due to the absence of the RSOI. However, for the antiparallel alignment, the spin-polarized AR occurs resulting from the crossed AR (CAR) and the RSOI. The effects of the coherent indirect coupling, RSOI, and magnetic flux on the Andreev-reflected tunneling magnetoresistance are analyzed at length. The spin-related current is calculated, and a distinct swap effect emerges. Furthermore, the pure spin current can be generated due to the CAR when two ferromagnets become two half metals. It is found that the strong RSOI and the large indirect coupling are in favor of the CAR and the production of the strong spin current. The properties of the spin-related current are tunable in terms of the external parameters. Our results offer new ways to manipulate the spin-dependent transport. PMID:23228047
NASA Astrophysics Data System (ADS)
Dutta, Paramita; Saha, Arijit; Jayannavar, A. M.
2016-11-01
We study the Aharonov-Bohm effect in a two-terminal helical ring with long-range hopping in the presence of Rashba spin-orbit interaction. We explore how the spin polarization behavior changes depending on the applied magnetic flux and the incoming electron energy. The most interesting feature that we articulate in this system is that zero-energy crossings appear in the energy spectra at Φ =0 and also at integer multiples of half-flux quantum values (n Φ0/2 ,n being an integer) of the applied magnetic flux. We investigate the transport properties of the ring using Green's function formalism and find that the zero-energy transmission peaks corresponding to those zero-energy crossings vanish in the presence of Rashba spin-orbit interaction. We also incorporate static random disorder in our system and show that the zero-energy crossings and transmission peaks are not immune to disorder even in the absence of Rashba spin-orbit interaction. The latter prevents the possibility of these helical states in the ring behaving like topological insulator edge states.
Bai, Long; Zhang, Rong; Duan, Chen-Long
2012-12-10
: Using the nonequilibrium Green's function method, we theoretically study the Andreev reflection(AR) in a four-terminal Aharonov-Bohm interferometer containing a coupled double quantum dot with the Rashba spin-orbit interaction (RSOI) and the coherent indirect coupling via two ferromagnetic leads. When two ferromagnetic electrodes are in the parallel configuration, the spin-up conductance is equal to the spin-down conductance due to the absence of the RSOI. However, for the antiparallel alignment, the spin-polarized AR occurs resulting from the crossed AR (CAR) and the RSOI. The effects of the coherent indirect coupling, RSOI, and magnetic flux on the Andreev-reflected tunneling magnetoresistance are analyzed at length. The spin-related current is calculated, and a distinct swap effect emerges. Furthermore, the pure spin current can be generated due to the CAR when two ferromagnets become two half metals. It is found that the strong RSOI and the large indirect coupling are in favor of the CAR and the production of the strong spin current. The properties of the spin-related current are tunable in terms of the external parameters. Our results offer new ways to manipulate the spin-dependent transport.
Exchange interaction and oscillations of the magnetization of the electron gas in a quantum cylinder
Eminov, P. A. Sezonov, Yu. I.; Al'pern, A. V.; Sal'nikov, N. V.
2006-10-15
The exchange energy of the electron gas on a cylindrical surface in a constant magnetic field has been calculated. Analytical formulas describing the contribution of the exchange interaction into oscillations of the magnetization of the electron gas in a quantum cylinder have been obtained. It is shown that the magnetic response of the system exhibits Aharonov-Bohm oscillations for both degenerate and Boltzmann electron gases.
Aharonov—Bohm Oscillations in Small Diameter Bi Nanowires
NASA Astrophysics Data System (ADS)
Konopko, L.
The Aharonov-Bohm effect (AB) exists in cylindrical wires as the magnetoresistance (MR) oscillations with a period ΔB that is proportional to Φ0 / S, where Φ0 = h / e is the flux quantum and S is the wire cross section. The AB-type longitudinal MR oscillations with period ΔB = Φ0 / S caused by electrons undergoing continuous grazing incidence at the wire wall have been observed previously at 4.2 K in single bismuth nanowires with a diameter 0. 2 < d < 0. 8 μm grown by the Ulitovsky technique. We present here our results of the observation of AB oscillations with period ΔB = h / e and ΔB = h / 2e on single Bi nanowires with a diameter d = 45-73 nm. The single nanowire samples were prepared by improved Ulitovsky technique and represented cylindrical single crystals with (1011) orientation along the wire axis. Due to very low effective masses of electrons and holes, electronic quantum confinement effects induce a semimetal-to-semiconductor transformation (SMSC) for wires with diameters below 50 nm. Our estimation of thermal energy gap from R(T) dependence for 50 nm Bi wire gives the value of 14 meV. The surface of Bi nanowire supports surface states, with carrier densities of around 5 ×1012 cm- 2 with strong spin-orbit interactions. From B ˜ 8 T down to B = 0, the extremums of h/2e oscillations are shifted up to 3π at B = 0, which is the manifestation of Berry phase shift. We connect the existence of h / 2e oscillations with weak localizations on surface states of Bi nanowires according to the Altshuller-Aronov-Spivak theory.
NASA Astrophysics Data System (ADS)
Akcay, Huseyin; Sever, Ramazan
2016-07-01
We investigate the energy spectrum and the corresponding eigenfunctions of a 2D Dirac oscillator confined by an antidot potential in the presence of a magnetic field and Aharonov-Bohm flux field. Analytical solutions are obtained and compared with the results of the Schrödinger equation found in the literature. Further, the dependence of the spectrum on the magnetic quantum number and on the repulsive potential is discussed.
Observation of quantum oscillations in FIB fabricated nanowires of topological insulator (Bi2Se3).
Bhattacharyya, Biplab; Sharma, Alka; Awana, V P S; Srivastava, A K; Senguttuvan, T D; Husale, Sudhir
2017-03-22
In the last few years, research based on topological insulators (TIs) has been of great interest due to their intrinsic exotic fundamental properties and potential applications such as quantum computers or spintronics. The fabrication of TI nanodevices and the study of their transport properties has mostly focused on high quality crystalline nanowires or nanoribbons. Here, we report a robust approach to Bi2Se3 nanowire formation from deposited flakes using an ion beam milling method. Fabricated Bi2Se3 nanowire devices were employed to investigate the robustness of the topological surface state (TSS) to gallium ion doping and any deformation in the material due to the fabrication tools. We report on the quantum oscillations in magnetoresistance (MR) curves under the parallel magnetic field. The resistance versus magnetic field curves are studied and compared with Aharonov-Bohm (AB) interference effects, which further demonstrate transport through the TSS. The fabrication route and observed electronic transport properties indicate clear quantum oscillations, and these can be exploited further in studying the exotic electronic properties associated with TI-based nanodevices.
Dirac oscillator interacting with a topological defect
Carvalho, J.; Furtado, C.; Moraes, F.
2011-09-15
In this work we study the interaction problem of a Dirac oscillator with gravitational fields produced by topological defects. The energy levels of the relativistic oscillator in the cosmic string and in the cosmic dislocation space-times are sensible to curvature and torsion associated to these defects and are important evidence of the influence of the topology on this system. In the presence of a localized magnetic field the energy levels acquire a term associated with the Aharonov-Bohm effect. We obtain the eigenfunctions and eigenvalues and see that in the nonrelativistic limit some results known in standard quantum mechanics are reached.
The electronic properties of concentric double quantum ring and possibility designing XOR gate
NASA Astrophysics Data System (ADS)
AL-Badry, Lafy. F.
2017-03-01
In this paper I have investigated the Aharonov-Bohm oscillation in concentric double quantum ring. The outer ring attached to leads while the inner ring only tunnel-coupled to the outer ring. The effect of inner ring on electron transport properties through outer ring studied and found that the conductance spectrum consists of two types of oscillations. One is the normal Aharonov-Bohm oscillation, and other is a small oscillations superposed above AB oscillation. The AB oscillation utilized to designing nanoscale XOR gate by choosing the magnetic flux and tuning the gate voltages which realization XOR gate action.
On the effects of a screw dislocation and a linear potential on the harmonic oscillator
NASA Astrophysics Data System (ADS)
Bueno, M. J.; Furtado, C.; Bakke, K.
2016-09-01
Quantum effects on the harmonic oscillator due to the presence of a linear scalar potential and a screw dislocation are investigated. By searching for bound states solutions, it is shown that an Aharonov-Bohm-type effect for bound states and a restriction of the values of the angular frequency of the harmonic oscillator can be obtained, where the allowed values are determined by the topology of the screw dislocation and the quantum numbers associated with the radial modes and the angular momentum. As particular cases, the angular frequency and the energy levels associated with the ground state and the first excited state of the system are obtained.
NASA Astrophysics Data System (ADS)
Gambaryan, K. M.; Harutyunyan, V. G.; Aroutiounian, V. M.; Ai, Y.; Ashalley, E.; Wang, Z. M.
2015-06-01
The InAsSbP composition type-II quantum dots (QDs) are grown on a InAs(1 0 0) substrate from In-As-Sb-P quaternary liquid phase at a constant temperature in Stranski-Krastanow growth mode. Device structures in the form of photoconductive cells are prepared for investigation. Magnetospectroscopy and high-precision capacitance spectrometry are used to explore the QDs structure’s electric sheet resistance in a magnetic field and the capacitance (charge) law at lateral current flow. Aharonov-Bohm (AB) oscillations with the period of δB = 0.38 ± 0.04 T are found on the magnetoresistance curve at both room and liquid nitrogen temperatures. The influence of the QDs size distribution on the period of AB oscillations is investigated. The magnetoresistance hysteresis equals to ~50 mΩ and ~400 mΩ is revealed at room and liquid nitrogen temperature, respectively. The capacitance hysteresis (CH) and contra-directional oscillations are also detected. Behavior of the CH versus applied voltage frequency in the range f = 103-106 Hz is investigated. It is shown that the CH decreases with increasing frequency up to 106 Hz. The time constant and corresponding frequency for the QDs R-C parallel circuit (generator) equal to τ = 2.9 × 10-7 s and f 0 = 5.5 × 105 Hz, respectively, are calculated.
Electronic Properties of Semimetal-Semiconductor (V/III-V) Heterostructures and Devices
2007-11-02
structures exhibiting negative differential resistances and Sb submicron loops displaying Aharonov - Bohm oscil- lations. 14. SUBJECT TERMS 17...resonant tunneling structures exhibiting negative differential resistances and Sb submicron loops displaying Aharonov - Bohm oscillations. B...structures were fabricated using ion beam milling techniques. Aharonov - Bohm effects were studied in a l|i.m diameter Sb loop. Variation of the sample
Aharonov-Bohm Effect in Perturbation Theory.
ERIC Educational Resources Information Center
Purcell, Kay M.; Henneberger, Walter C.
1978-01-01
The Aharonov-Bohn effect is obtained in first-order perturbation theory. It is shown that the effect occurs only when the initial state is a superposition of eigenstates of Lz corresponding to eigenvalues having opposite sign. (Author/GA)
Klein-Gordon oscillator in Kaluza-Klein theory
NASA Astrophysics Data System (ADS)
Carvalho, Josevi; Carvalho, Alexandre M. de M.; Cavalcante, Everton; Furtado, Claudio
2016-07-01
In this contribution we study the Klein-Gordon oscillator on the curved background within the Kaluza-Klein theory. The problem of the interaction between particles coupled harmonically with topological defects in Kaluza-Klein theory is studied. We consider a series of topological defects, then we treat the Klein-Gordon oscillator coupled to this background, and we find the energy levels and corresponding eigenfunctions in these cases. We show that the energy levels depend on the global parameters characterizing these spacetimes. We also investigate a quantum particle described by the Klein-Gordon oscillator interacting with a cosmic dislocation in Som-Raychaudhuri spacetime in the presence of homogeneous magnetic field in a Kaluza-Klein theory. In this case, the energy spectrum is determined, and we observe that these energy levels represent themselves as the sum of the terms related with Aharonov-Bohm flux and of the parameter associated to the rotation of the spacetime.
Quantum interference and decoherence in hexagonal antidot lattices
NASA Astrophysics Data System (ADS)
Iye, Yasuhiro; Ueki, Masaaki; Endo, Akira; Katsumoto, Shingo
2003-09-01
The Altshuler-Aronov-Spivak (AAS) oscillations and the Aharonov-Bohm (AB) type oscillations both at low and high magnetic fields were observed in hexagonal antidot lattices fabricated from a GaAs/AlGaAs two-dimensional electron gas sample. The periodicities in the magnetic field and in the gate bias voltage, of the high field AB oscillation furnish information on the edge states localized around the antidots. The temperature dependences of these quantum oscillations are studied.
Conductance oscillations of core-shell nanowires in transversal magnetic fields
NASA Astrophysics Data System (ADS)
Manolescu, Andrei; Nemnes, George Alexandru; Sitek, Anna; Rosdahl, Tomas Orn; Erlingsson, Sigurdur Ingi; Gudmundsson, Vidar
2016-05-01
We analyze theoretically electronic transport through a core-shell nanowire in the presence of a transversal magnetic field. We calculate the conductance for a variable coupling between the nanowire and the attached leads and show how the snaking states, which are low-energy states localized along the lines of the vanishing radial component of the magnetic field, manifest their existence. In the strong-coupling regime they induce flux periodic, Aharonov-Bohm-like, conductance oscillations, which, by decreasing the coupling to the leads, evolve into well-resolved peaks. The flux periodic oscillations arise due to interference of the snaking states, which is a consequence of backscattering at either the contacts with leads or magnetic or potential barriers in the wire.
Electronic Transport Control of Bi Nanowires
2007-09-07
TERMS night vision coolers, thermoelectrics, nanowires, bismuth, Aharonov Bohm , quantum, confinement Tito E. Huber Howard University Office Of...journals or in conference proceedings (N/A for none) Quantum Interference of Surface States in Bismuth Nanowires probed by the Aharonov - Bohm Oscillation of...indications that this in indeed the case because the nanowires exhibit Aharonov - Bohm oscillations that are generally observed in tubes or rings. 6
Quantum Phenomena in Semiconductor Structures
1988-04-01
observed by changing the magnetic field through the loop, which changes the phase of the wavefunction, due to the Aharonov - Bohm effect. The...fields (<IT), in order to determine the dependence of the Aharonov - Bohm (AB) effect on channel width and field. The Quantum Hall Effect was studied at...interference may be observed through the addition of an extra phase difference between the two waves. The Aharonov - Bohm effect gives rise to such a phase
Measuring the momentum of a nanomechanical oscillator using tunnel junctions
NASA Astrophysics Data System (ADS)
Doiron, Charles; Trauzettel, Bjoern; Bruder, Christoph
2008-03-01
We present a way to measure the momentum p of a nanomechanical oscillatorootnotetextC. B. Doiron, B. Trauzettel, C. Bruder. arXiv:0707.2709.. The momentum detector is based on two tunnel junctions in an Aharonov-Bohm-type setup, where one of the tunneling amplitudes depends on the motion of the oscillator and the other one does not. The coupling between the first tunnel junction and the oscillator is assumed to be linear in the position x of the oscillator t(x) = t0+ t1x. However, the presence of two junctions can, under certain conditions, lead to an effective imaginary coupling t(x) = t0+ i t1x. By calculating the equation-of-motion for the density matrix of the coupled (oscillator+tunnel junction) systemootnotetextA.A Clerk, S. Girvin. Phys. Rev. B 70, 121303 (2004)., we show that in this case the finite-frequency current noise of the detector is proportional to the momentum spectrum of the oscillator.
Self-oscillating AB diblock copolymer developed by post modification strategy
Ueki, Takeshi E-mail: ryo@cross.t.u-tokyo.ac.jp; Onoda, Michika; Tamate, Ryota; Yoshida, Ryo E-mail: ryo@cross.t.u-tokyo.ac.jp; Shibayama, Mitsuhiro
2015-06-15
We prepared AB diblock copolymer composed of hydrophilic poly(ethylene oxide) segment and self-oscillating polymer segment. In the latter segment, ruthenium tris(2,2′-bipyridine) (Ru(bpy){sub 3}), a catalyst of the Belousov-Zhabotinsky reaction, is introduced into the polymer architecture based on N-isopropylacrylamide (NIPAAm). The Ru(bpy){sub 3} was introduced into the polymer segment by two methods; (i) direct random copolymerization (DP) of NIPAAm and Ru(bpy){sub 3} vinyl monomer and (ii) post modification (PM) of Ru(bpy){sub 3} with random copolymer of NIPAAm and N-3-aminopropylmethacrylamide. For both the diblock copolymers, a bistable temperature region (the temperature range; ΔT{sub m}), where the block copolymer self-assembles into micelle at reduced Ru(bpy){sub 3}{sup 2+} state whereas it breaks-up into individual polymer chain at oxidized Ru(bpy){sub 3}{sup 3+} state, monotonically extends as the composition of the Ru(bpy){sub 3} increases. The ΔT{sub m} of the block copolymer prepared by PM is larger than that by DP. The difference in ΔT{sub m} is rationalized from the statistical analysis of the arrangement of the Ru(bpy){sub 3} moiety along the self-oscillating segments. By using the PM method, the well-defined AB diblock copolymer having ΔT{sub m} (ca. 25 °C) large enough to cause stable self-oscillation can be prepared. The periodic structural transition of the diblock copolymer in a dilute solution ([Polymer] = 0.1 wt. %) is closely investigated in terms of the time-resolved dynamic light scattering technique at constant temperature in the bistable region. A macroscopic viscosity oscillation of a concentrated polymer solution (15 wt. %) coupled with the periodic microphase separation is also demonstrated.
Quantum Phenomena in Semiconductor Structures
1988-12-13
oscillated with magnetic flux - the Aharonov - Bohm effect - and was investigated in detail. Evidence of interference was also found between electrons...Transistors", T P C Judd, M Pepper and G Hill, AppI. Phys. Lett. U3, 54, 1988. 5. ’The Aharonov - Bohm Effect in Electrostatically Defined Heterojunction
Aharonov-Bohm effect on Aharonov-Casher scattering
NASA Astrophysics Data System (ADS)
Lin, Qiong-Gui
2010-01-01
The scattering of relativistic spin-1/2 neutral particles with a magnetic dipole moment by a long straight charged line and a magnetic flux line at the same position is studied. The scattering cross sections for unpolarized and polarized particles are obtained by solving the Dirac-Pauli equation. The results are in general the same as those for pure Aharonov-Casher scattering (by the charged line alone) as expected. However, in special cases when the incident energy, the line charge density, and the magnetic flux satisfy some relations, the cross section for polarized particles is dramatically changed. Relations between the polarization of incident particles and that of scattered ones are presented, both in the full relativistic case and the nonrelativistic limit. The characteristic difference between the general and special cases lies in the backward direction: in the general cases the incident particles are simply bounced while in the special cases their polarization is turned over simultaneously. For pure Aharonov-Casher scattering there exist cases where the helicities of all scattered particles are reversed. This seems to be remarkable but appears unnoticed previously. Two mathematical approaches are employed to deal with the singularity of the electric and magnetic field and it turns out that the physical results are essentially the same.
Induced current and Aharonov-Bohm effect in graphene
NASA Astrophysics Data System (ADS)
Jackiw, R.; Milstein, A. I.; Pi, S.-Y.; Terekhov, I. S.
2009-07-01
The effect of vacuum polarization in the field of an infinitesimally thin solenoid at distances much larger than the radius of solenoid is investigated. The induced charge density and induced current are calculated. Though the induced charge density turned out to be zero, the induced current is a finite periodical function of the magnetic flux Φ . The expression for this function is found exactly in a value of the flux. The induced current is equal to zero at the integer values of Φ/Φ0 as well as at half-integer values of this ratio, where Φ0=2πℏc/e is the elementary magnetic flux. The latter is a consequence of the Furry theorem and periodicity of the induced current with respect to magnetic flux. As an example we consider the graphene in the field of solenoid perpendicular to the plane of a sample.
Semifluxon degeneracy choreography in Aharonov-Bohm billiards
NASA Astrophysics Data System (ADS)
Berry, M. V.; Popescu, S.
2010-09-01
Every energy level of a charged quantum particle confined in a region threaded by a magnetic flux line with quantum flux one-half must be degenerate for some position of the semifluxon within the boundary B. This is illustrated by computations for which B is a circle and a conformal transformation of a circle without symmetry. As the shape of B is varied, two degeneracies between the same pair of levels can collide and annihilate. Degeneracy of three levels requires three shape parameters, or the positions of three semifluxons; degeneracy of N levels can be generated by int{N(N + 1)/4} semifluxons. The force on the semifluxon is derived.
Aharonov-Bohm phase in high density quark matter
NASA Astrophysics Data System (ADS)
Chatterjee, Chandrasekhar; Nitta, Muneto
2016-03-01
Stable non-Abelian vortices, which are color magnetic flux tubes as well as superfluid vortices, are present in the color-flavor locked phase of dense quark matter with diquark condensations. We calculate the Aharanov-Bohm phases of charged particles, that is, electrons, muons, and color-flavor locked mesons made of tetraquarks around a non-Abelian vortex.
The Aharonov-Bohm effect and classical potentials
Mijatovic, M.; Trencevski, K.; Veljanoski, B.
1993-06-01
Using the inverse scattering method we derive the classical potential which produces the same cross section as the Ahaxonov-Bohm effect. Because the potential is velocity dependent it shows that this effect of quantum scattering theory can reduce to non-potential classical mechanics, only. 7 refs., 3 figs.
Aharonov-Bohm effect on Aharonov-Casher scattering
Lin Qionggui
2010-01-15
The scattering of relativistic spin-1/2 neutral particles with a magnetic dipole moment by a long straight charged line and a magnetic flux line at the same position is studied. The scattering cross sections for unpolarized and polarized particles are obtained by solving the Dirac-Pauli equation. The results are in general the same as those for pure Aharonov-Casher scattering (by the charged line alone) as expected. However, in special cases when the incident energy, the line charge density, and the magnetic flux satisfy some relations, the cross section for polarized particles is dramatically changed. Relations between the polarization of incident particles and that of scattered ones are presented, both in the full relativistic case and the nonrelativistic limit. The characteristic difference between the general and special cases lies in the backward direction: in the general cases the incident particles are simply bounced while in the special cases their polarization is turned over simultaneously. For pure Aharonov-Casher scattering there exist cases where the helicities of all scattered particles are reversed. This seems to be remarkable but appears unnoticed previously. Two mathematical approaches are employed to deal with the singularity of the electric and magnetic field and it turns out that the physical results are essentially the same.
Nonequilibrium work statistics of an Aharonov-Bohm flux.
Yi, Juyeon; Talkner, Peter; Campisi, Michele
2011-07-01
We investigate the statistics of work performed on a noninteracting electron gas confined in a ring as a threaded magnetic field is turned on. For an electron gas initially prepared in a grand canonical state it is demonstrated that the Jarzynski equality continues to hold in this case, with the free energy replaced by the grand potential. The work distribution displays a marked dependence on the temperature. While in the classical (high-temperature) regime, the work probability density function follows a Gaussian distribution and the free energy difference entering the Jarzynski equality is null, the free energy difference is finite in the quantum regime, and the work probability distribution function becomes multimodal. We point out the dependence of the work statistics on the number of electrons composing the system.
Malbon, Christopher L; Zhu, Xiaolei; Guo, Hua; Yarkony, David R
2016-12-21
For two electronic states coupled by conical intersections, the line integral of the derivative coupling can be used to construct a complex-valued multiplicative phase factor that makes the real-valued adiabatic electronic wave function single-valued, provided that the curl of the derivative coupling is zero. Unfortunately for ab initio determined wave functions, the curl is never rigorously zero. However, when the wave functions are determined from a coupled two diabatic state Hamiltonian H(d) (fit to ab initio data), the resulting derivative couplings are by construction curl free, except at points of conical intersection. In this work we focus on a recently introduced diabatization scheme that produces the H(d) by fitting ab initio determined energies, energy gradients, and derivative couplings to the corresponding H(d) determined quantities in a least squares sense, producing a removable approximation to the ab initio determined derivative coupling. This approach and related numerical issues associated with the nonremovable ab initio derivative couplings are illustrated using a full 33-dimensional representation of phenol photodissociation. The use of this approach to provide a general framework for treating the molecular Aharonov Bohm effect is demonstrated.
NASA Astrophysics Data System (ADS)
Malbon, Christopher L.; Zhu, Xiaolei; Guo, Hua; Yarkony, David R.
2016-12-01
For two electronic states coupled by conical intersections, the line integral of the derivative coupling can be used to construct a complex-valued multiplicative phase factor that makes the real-valued adiabatic electronic wave function single-valued, provided that the curl of the derivative coupling is zero. Unfortunately for ab initio determined wave functions, the curl is never rigorously zero. However, when the wave functions are determined from a coupled two diabatic state Hamiltonian Hd (fit to ab initio data), the resulting derivative couplings are by construction curl free, except at points of conical intersection. In this work we focus on a recently introduced diabatization scheme that produces the Hd by fitting ab initio determined energies, energy gradients, and derivative couplings to the corresponding Hd determined quantities in a least squares sense, producing a removable approximation to the ab initio determined derivative coupling. This approach and related numerical issues associated with the nonremovable ab initio derivative couplings are illustrated using a full 33-dimensional representation of phenol photodissociation. The use of this approach to provide a general framework for treating the molecular Aharonov Bohm effect is demonstrated.
Ab initio oscillator strengths and transition probabilities in oxygen-like Cr XVII
Bogdanovich, P.; Karpuskiene, R.
2008-09-15
Ab initio energy spectra of the ground configuration 2s{sup 2}2p{sup 4}, the excited configurations 2s2p{sup 5}, 2p{sup 6}, 2s{sup 2}2p{sup 3}3s, 2s{sup 2}2p{sup 3}3p, 2s{sup 2}2p{sup 3}3d, 2s2p{sup 4}3s, 2s2p{sup 4}3p, and 2s2p{sup 4}3d of oxygen-like chromium Cr XVII have been calculated using the configuration interaction method. The wavelengths, oscillator strengths and the emission transition probabilities from configurations 2s{sup 2}2p{sup 3}3l and 2s2p{sup 4}3l are obtained. The radiative lifetimes of excited levels are also presented.0.
Ensemble Averaging in Metallic Quantum Networks
NASA Astrophysics Data System (ADS)
Mallet, François; Schopfer, Félicien; Ericsson, Jerry; Saminadayar, Laurent; Bäuerle, Christopher; Mailly, Dominique; Texier, Christophe; Montambaux, Gilles
2008-10-01
We report on the size dependence of the amplitudes of Aharonov-Bohm (AB) as well as Altshuler-Aronov-Spivak (AAS) magnetoconductance oscillations in silver networks with anisotropic aspect ratio and for various sizes ranging from 10 to 106 plaquettes. We show that the amplitude of both AB and AAS oscillations exhibit an unexpected dependence as a function of number of plaquettes N when the smallest dimension of the network becomes smaller than the phase coherence length: in this case, the network can be considered as a fully coherent object (mesoscopic) in one direction, whereas macroscopic in the other.
NASA Astrophysics Data System (ADS)
Kreisbeck, C.; Kramer, T.; Molina, R. A.
2017-04-01
We have performed time-dependent wave packet simulations of realistic Aharonov-Bohm (AB) devices with a quantum dot embedded in one of the arms of the interferometer. The AB ring can function as a measurement device for the intrinsic transmission phase through the quantum dot, however, care has to be taken in analyzing the influence of scattering processes in the junctions of the interferometer arms. We consider a harmonic quantum dot and show how the Darwin–Fock spectrum emerges as a unique pattern in the interference fringes of the AB oscillations.
NASA Astrophysics Data System (ADS)
Kang, Ning; Abe, Eisuke; Hashimoto, Yoshiaki; Iye, Yasuhiro; Katsumoto, Shingo
2007-08-01
We report a study of the Aharonov-Bohm (AB) type oscillation of weak field magnetoresistance in an anti-dot lattice (ADL) of a two-dimensional hole system in the presence of strong spin-orbit interaction. The Fourier transform of the oscillations reveals non-monotonic evolutions with the different range of harmonic component, which are indicative of the existence of additional phase factors. A simulation considering Berry’s phase and the phase arising from the spin-orbit shift in the momentum space shows qualitative agreement with the experiment.
NASA Astrophysics Data System (ADS)
Li, Hai-Tao; Liu, Li-Zhe; Liu, Jian-Jun
2008-11-01
We calculate the energy states and Aharonov-Bohm oscillations of an electron in elliptical quantum rings in the presence of a uniform magnetic Geld by using an exact numerical diagonalization. The calculated results show that the elliptical quantum rings are flatter, larger amplitudes and periods of the Aharonov-Bohm oscillations are observed. In addition, in the limits of a circular quantum ring, the results of our approach are in good agreement with those of earlier theories.
Superconductivity of the magnetized electron gas of a quantum cylinder
Eminov, P. A. Sezonov, Yu. I.
2008-10-15
A microscopic theory of superconductivity is developed for the magnetized electron gas on a cylindrical surface. The Gibbs free energy is calculated for the superconducting system. A gap equation is derived that determines the critical temperature as a function of the quantum-cylinder dimensions and the Aharonov-Bohm parameter. It is shown that the gap not only exhibits Aharonov-Bohm oscillations, but also oscillates with varying curvature of the cylindrical surface.
NASA Astrophysics Data System (ADS)
Poniedziałek, M. R.; Szafran, B.
2012-02-01
We study the electron transport in three terminal junctions and quantum rings looking for the classical deflection of electron trajectories in the presence of intersubband scattering. We indicate that although the Aharonov-Bohm oscillations and the Lorentz force effects co-exist in the low subband transport, for higher Fermi energies a simultaneous observation of both effects is difficult and calls for carefully formed structures. In particular, in quantum rings with channels wider than the input lead the Lorentz force is well resolved but the Aharonov-Bohm periodicity is lost in chaotic scattering events. In quantum rings with equal lengths of the channels and T-shaped junctions the Aharonov-Bohm oscillations are distinctly periodic but the Lorentz force effects are not well pronounced. We find that systems with wedge-shaped junctions allow for observation of both the periodic Aharonov-Bohm oscillations and the magnetic deflection.
Extended AB period study of the electron pairing transition in t-J ladders
Kusakabe, Koichi; Aoki, Hideo
1996-11-01
The extended Aharonov-Bohm period test, recently proposed by the present authors, is used to study the electron pairing transition in the t-J ladders. The critical point is detected as a gap opening in the extended spectral flow. The result suggests a pairing prior to the onset of a phase separation, which is consistent with a recent Tomonaga-Luttinger analysis.
Ab initio study of the SeS local oscillator in zinc sulfide
NASA Astrophysics Data System (ADS)
Petzke, K.
1999-11-01
A method is presented to calculate the energy and symmetry of local vibrational modes (LVM's) at point defects in semiconductors from first principles. The force constants for the disturbed and undisturbed systems are calculated using a variant of the direct approach. The ab initio results are used as input parameters for a cluster simulation with up to 489 vibrating atoms, which accounts for hybridization effects between the LVM and the host lattice modes. The method is applied to the LVM of ZnS:SeS, which shows a pronounced fine structure due to both host and ligand induced isotope effects. The energy of the main peak, which represents the most abundant Selen isotope 80Se, is calculated as 229.6 cm-1. This agrees very well with the result of 229.2 cm-1 from Fourier transform infrared experiments found in the literature. It is shown that the ab initio result improves the understanding of the LVM, when compared to the previously used ad hoc model, especially in the low-energy region.
Ab initio oscillator strengths and transition probabilities in aluminum-like calcium, Ca VIII
Karpuskiene, R. Bogdanovich, P.
2009-07-15
An ab initio study of aluminum-like calcium is presented. The calculations are performed within the configuration interaction method in the basis of transformed radial orbitals with a variable parameter. Relativistic effects are accounted for within the Breit-Pauli approximation. Energy spectra, transition characteristics and lifetimes of excited levels of configurations 3s{sup 2}3p, 3s3p{sup 2}, 3s{sup 2}3d, 3p{sup 3}, 3s3p3d, 3p{sup 2}3d, 3s{sup 2}4s, 3s{sup 2}4p, 3s{sup 2}4d, 3s{sup 2}4f, 3s3p4s, and 3s3p4p are obtained. The results are compared with available experimental and theoretical data.
Quantum interference in an electron-hole graphene ring system
Smirnov, D.; Schmidt, H.; Haug, R. J.
2013-12-04
Quantum interference is observed in a graphene ring system via the Aharonov Bohm effect. As graphene is a gapless semiconductor, this geometry allows to study the unique situation of quantum interference between electrons and holes in addition to the unipolar quantum interference. The period and amplitude of the observed Aharonov-Bohm oscillations are independent of the sign of the applied gate voltage showing the equivalence between unipolar and dipolar interference.
Comment on "Aharonov-Casher and Scalar Aharonov-Bohm Topological Effects"
NASA Astrophysics Data System (ADS)
Choi, Taeseung; Cho, Sam Young
2014-04-01
In this Comment we point out (i) that the Hamiltonian, Eq. (17) in the Letter(Phys. Rev. Lett. 108, 070405 (2012)), is not a relativistic Hamiltonian, (ii) then that the conditions in the Letter are irrelevant for a topological AC and SAB effects, and (iii) conclusively that the non-relativistic Hamiltonian employed by Peshkin and Lipkin (Phys. Rev. Lett. 74, 2847 (1995)) has the same $U(1)_{mm}$ gauge structure for a fixed spin and then is not wrong, but their incorrect interpretation of the spin autocorrelations led to the incorrect conclusion.
Conductance phases in the quantum dots of an Aharonov-Bohm ring
NASA Astrophysics Data System (ADS)
Yahalom, A.; Englman, R.
2006-09-01
The regimes of growing phases (for electron numbers N≈0 8 ) that pass into regions of self-returning phases (for N>8 ), found recently in quantum dot conductances by Heiblum and co-workers are accounted for by an elementary Green’s function formalism, appropriate to an equi-spaced ladder structure (with at least three rungs) of electronic levels in the quantum dot. The key features of the theory are physically a dissipation rate that increases linearly with the level number (and is tentatively linked to coupling to longitudinal optical phonons) and a set of Fano-like metastable levels, which disturb the unitarity, and mathematically the changeover of the position of the complex transmission amplitude zeros from the upper half in the complex gap-voltage plane to the lower half of that plane. The two regimes are identified with (respectively) the Blaschke term and the Kramers-Kronig integral term in the theory of complex variables.
Random Aharonov Bohm vortices and some exact families of integrals: II
NASA Astrophysics Data System (ADS)
Mashkevich, Stefan; Ouvry, Stéphane
2008-03-01
At sixth order in perturbation theory, the random magnetic impurity problem at second order in impurity density narrows down to the evaluation of a single Feynman diagram with maximal impurity line crossing. This diagram can be rewritten as a sum of ordinary integrals and nested double integrals of products of the modified Bessel functions Kν and Iν, with ν = 0,1. That sum, in turn, is shown to be a linear combination with rational coefficients of (25-1)ζ(5), \\int_0^{\\infty }u \\,K_0(u)^6\\,\\rmd u , and \\int_0^{\\infty }u^3 K_0(u)^6\\,\\rmd u . Unlike what happens at lower orders, these two integrals are not linear combinations with rational coefficients of Euler sums, even though they appear in combination with ζ(5). On the other hand, any integral \\int_0^{\\infty }u^{n+1} K_0(u)^p (uK_1(u))^q \\,\\rmd u with weight p+q = 6 and an even n is shown to be a linear combination with rational coefficients of the above two integrals and 1, a result that can be easily generalized to any weight p+q = k. A matrix recurrence relation in n is built for such integrals. The initial conditions are such that the asymptotic behavior is determined by the smallest eigenvalue of the transition matrix.
Comment on "Role of potentials in the Aharonov-Bohm effect"
NASA Astrophysics Data System (ADS)
Aharonov, Yakir; Cohen, Eliahu; Rohrlich, Daniel
2015-08-01
Are the electromagnetic scalar and vector potentials dispensable? Vaidman [Phys. Rev. A 86, 040101(R) (2012)], 10.1103/PhysRevA.86.040101 has suggested that local interactions of gauge-invariant quantities, e.g., magnetic torques, suffice for the description of all quantum electromagnetic phenomena. We analyze six thought experiments that challenge this suggestion. All of them have explanations in terms of local interactions of gauge-dependent quantities, and, in addition, some have explanations in terms of nonlocal interactions of gauge-invariant quantities. We claim, however, that two of our examples have no gauge-invariant formal description and that, in general, no local description can dispense with electromagnetic potentials.
Single electron bipolar conductance switch driven by the molecular Aharonov-Bohm effect.
Lee, Joonhee; Tallarida, Nicholas; Rios, Laura; Perdue, Shawn M; Apkarian, Vartkess Ara
2014-06-24
We demonstrate a conductance switch controlled by the spin-vibronic density of an odd electron on a single molecule. The junction current is modulated by the spin-flip bistability of the electron. Functional images are provided as wiring diagrams for control of the switch's frequency, amplitude, polarity, and duty-cycle. The principle of operation relies on the quantum mechanical phase associated with the adiabatic circulation of a spin-aligned electron around a conical intersection. The functional images quantify the governing vibronic Hamiltonian.
Exciton storage in a nanoscale Aharonov-Bohm ring with electric field tuning.
Fischer, Andrea M; Campo, Vivaldo L; Portnoi, Mikhail E; Römer, Rudolf A
2009-03-06
We study analytically the optical properties of a simple model for an electron-hole pair on a ring subjected to perpendicular magnetic flux and in-plane electric field. We show how to tune this excitonic system from optically active to optically dark as a function of these external fields. Our results offer a simple mechanism for exciton storage and readout.
Aharonov-Bohm interference in neutral excitons: effects of built-in electric fields.
Teodoro, M D; Campo, V L; Lopez-Richard, V; Marega, E; Marques, G E; Gobato, Y Galvão; Iikawa, F; Brasil, M J S P; Abuwaar, Z Y; Dorogan, V G; Mazur, Yu I; Benamara, M; Salamo, G J
2010-02-26
We report a comprehensive discussion of quantum interference effects due to the finite structure of neutral excitons in quantum rings and their first experimental corroboration observed in the optical recombinations. The signatures of built-in electric fields and temperature on quantum interference are demonstrated by theoretical models that describe the modulation of the interference pattern and confirmed by complementary experimental procedures.
Exciton Storage in a Nanoscale Aharonov-Bohm Ring with Electric Field Tuning
Fischer, Andrea M.; Roemer, Rudolf A.; Campo, Vivaldo L. Jr.; Portnoi, Mikhail E.
2009-03-06
We study analytically the optical properties of a simple model for an electron-hole pair on a ring subjected to perpendicular magnetic flux and in-plane electric field. We show how to tune this excitonic system from optically active to optically dark as a function of these external fields. Our results offer a simple mechanism for exciton storage and readout.
Effects of interactions in transport through Aharonov-Bohm-Casher interferometers.
Lobos, A M; Aligia, A A
2008-01-11
We study the conductance through a ring described by the Hubbard model (such as an array of quantum dots), threaded by a magnetic flux and subject to Rashba spin-orbit coupling (SOC). We develop a formalism that is able to describe the interference effects as well as the Kondo effect when the number of electrons in the ring is odd. In the Kondo regime, the SOC reduces the conductance from the unitary limit, and, in combination with the magnetic flux, the device acts as a spin polarizer.
Exciton storage in type-II quantum dots using the optical Aharonov-Bohm effect
Climente, Juan I.; Planelles, Josep
2014-05-12
We investigate the bright-to-dark exciton conversion efficiency in type-II quantum dots subject to a perpendicular magnetic field. To this end, we take the exciton storage protocol recently proposed by Simonin and co-workers [Phys. Rev. B 89, 075304 (2014)] and simulate its coherent dynamics. We confirm the storage is efficient in perfectly circular structures subject to weak external electric fields, where adiabatic evolution is dominant. In practice, however, the efficiency rapidly degrades with symmetry lowering. Besides, the use of excited states is likely unfeasible owing to the fast decay rates. We then propose an adaptation of the protocol which does not suffer from these limitations.
Quantum Phenomena Observed Using Electrons
Tonomura, Akira
2011-05-06
Electron phase microscopy based on the Aharonov-Bohm (AB) effect principle has been used to illuminate fundamental phenomena concerning magnetism and superconductivity by visualizing quantitative magnetic lines of force. This paper deals with confirmation experiments on the AB effect, the magnetization process of tiny magnetic heads for perpendicular recording, and vortex behaviors in high-Tc superconductors.
Quantum mechanical effects of topological origin
NASA Technical Reports Server (NTRS)
Duru, I. H.
1993-01-01
Following a brief review of the original Casimir and Aharonov-Bohm effects, some other effects of similar natures are mentioned. A Casimir interaction between AB fluxes is presented. Possible realizations of the Casimir effects for massive charged fields in solid state structures and a new AB effect for photons are suggested.
Strong dependence of multichannel ballistic transport on the geometric symmetry
NASA Astrophysics Data System (ADS)
Shin, M.; Park, K. W.; Lee, S.; Lee, E.-H.
1998-01-01
Ballistic electron transport in Aharonov-Bohm-type ring structures is investigated where the single-channel problem is nontrivially extended to the multichannel one in which the important interchannel scattering effect is considered. It is found that theS-matrix of a ring structure should reflect the geometric symmetry if the interchannel scattering effect is properly accounted for and that the symmetry relationships of theS-matrix plays a crucial role in the conductance oscillation behavior in ballistic two-dimensional rings. The magnetostatic as well as the electrostatic Aharonov-Bohm effects are studied for two ring structures of different symmetry.
Magnetoexciton in nanotube under external electric field
NASA Astrophysics Data System (ADS)
Garcia Russi, L. F.; Paredes Gutiérrez, H.; Santos, Y. F.; Mikhailov, I. D.
2016-08-01
We study the Aharonov-Bohm oscillation of the energy levels of an electron-hole pair confined in a narrow nanotube in the presence of the magnetic field applied along the symmetry axis. We show that the electric field applied at the same direction makes the oscillation more pronounced.
Spin Interference In Silicon One-Dimensional Rings
NASA Astrophysics Data System (ADS)
Bagraev, N. T.; Galkin, N. G.; Gehlhoff, W.; Klyachkin, L. E.; Malyarenko, A. M.; Shelykh, I. A.
2010-01-01
We present the first findings of the spin transistor effect in the Rashba gate-controlled ring embedded in the p-type self-assembled silicon quantum well that is prepared on the n-type Si (100) surface. Firstly, the amplitude and phase sensitivity of the "0.7ṡ(2 e2/h)" feature of the hole quantum conductance staircase revealed by the quantum point contact inserted in the one of the arms of the double-slit ring are found to result from the Aharonov-Bohm (AB) and Aharonov-Casher (AC) conductance oscillations by varying respectively the value of the external magnetic field and the top-gate bias voltage. Secondly, the "0.7ṡ(2 e2/h)" feature appears to exhibit the fractional form revealed by both the plateuas and steps as a function of the top-gate bias voltage, with the variations of their positions in the external magnetic field.
Energy levels and far-infrared spectra of oval-shaped nanorings
Gutiérrez, W.; García, L. F.; Mikhailov, I. D.
2014-05-15
The evolution of the Aharonov-Bohm oscillation of low-lying states and far infrared spectrum associated to variation of the path curvature for electron motion along nanorings with centerlines in a form of a set of Cassini ovals, whose shape is changed continuously from a single elongated loop to two separated loops is theoretically investigated.
Quantum interference effects in topological nanowires in a longitudinal magnetic field
NASA Astrophysics Data System (ADS)
Sacksteder, Vincent E.; Wu, Quansheng
2016-11-01
We study the magnetoconductance of topological insulator nanowires in a longitudinal magnetic field, including Aharonov-Bohm, Altshuler-Aronov-Spivak, perfectly conducting channel, and universal conductance fluctuation effects. Our focus is on predicting experimental behavior in single wires in the quantum limit where temperature is reduced to zero. We show that changing the Fermi energy EF can tune a wire from from ballistic to diffusive conduction and to localization. In both ballistic and diffusive single wires we find both Aharonov-Bohm and Altshuler-Aronov-Spivak oscillations with similar strengths, accompanied by quite strong universal conductance fluctuations, all with amplitudes between 0.3 G0 and 1 G0 . This contrasts strongly with the average behavior of many wires, which shows Aharonov-Bohm oscillations in the ballistic regime and Altshuler-Aronov-Spivak oscillations in the diffusive regime, with both oscillations substantially larger than the conductance fluctuations. In single wires the ballistic and diffusive regimes can be distinguished by varying EF and studying the sign of the Aharonov-Bohm signal, which depends periodically on EF in ballistic wires and randomly on EF in diffusive wires. We also show that in long wires the perfectly conducting channel is visible at a wide range of energies within the bulk gap. We present typical conductance profiles at several wire lengths, showing that conductance fluctuations can dominate the average signal. Similar behavior will be found in carbon nanotubes.
Dmitriev, A P; Gornyi, I V; Kachorovskii, V Yu; Polyakov, D G
2010-07-16
We study the effect of electron-electron interaction on transport through a tunnel-coupled single-channel ring. We find that the conductance as a function of magnetic flux shows a series of interaction-induced resonances that survive thermal averaging. The period of the series is given by the interaction strength α. The physics behind this behavior is the blocking of the tunneling current by the circular current. The main mechanism of dephasing is due to circular-current fluctuations. The dephasing rate is proportional to the tunneling rate and does not depend on α.
NASA Astrophysics Data System (ADS)
Englman, R.
2016-08-01
The recent phase shift data of Takada et al. (Phys. Rev. Lett. 113 (2014) 126601) for a two level system are reconstructed from their current intensity curves by the method of Hilbert transform, for which the underlying Physics is the principle of causality. An introductory algebraic model illustrates pedagogically the working of the method and leads to newly derived relationships involving phenomenological parameters, in particular for the sign of the phase slope between the resonance peaks. While the parametrization of the experimental current intensity data in terms of a few model parameters shows only a qualitative agreement for the phase shift, due to the strong impact of small, detailed variations in the experimental intensity curve on the phase behavior, the numerical Hilbert transform yields a satisfactory reproduction of the phase.
Moulopoulos, Konstantinos; Constantinou, Martha
2004-12-15
By using a Green's function procedure we determine exactly the energy spectrum and the associated eigenstates of a system of two oppositely charged particles interacting through a contact potential and moving in a one-dimensional ring threaded by a magnetic flux. Critical interactions for the appearance of bound states are analytically determined and are viewed as limiting cases of many-body results from the area of interaction-induced metal-insulator transitions in charged quantal mixtures. Analytical expressions on one-body probability and charge current densities for this overall neutral system are derived and their single-valuedness leads to the possibility of states with broken symmetry, with possible experimental signatures in exciton spectra. Persistent currents are analytically determined and their properties investigated from the point of view of an interacting mesoscopic system. A cyclic adiabatic process on the interaction potential is also identified, with the associated Berry's phase directly linked to the electric (persistent) currents, the probability currents having no contribution for a neutral system.
Numerical simulations of a ballistic spin interferometer with Rashba spin-orbital interaction
NASA Astrophysics Data System (ADS)
Zhu, Zhenyue; Sun, Qing-Feng; Chen, Bin; Xie, X. C.
2006-08-01
We numerically investigate the transport behavior of a quasi-one-dimensional (1D) square loop device containing the Rashba spin-orbital interaction in the presence of a magnetic flux. The conductance versus the magnetic field shows the Al’tshuler-Aronov-Spivak (AAS) and Aharonov-Bohm (AB) oscillations. We focus on the oscillatory amplitudes, and find that both of them are strongly dependent on the spin precession angle (i.e., the strength of the spin-orbit interaction) and exhibit no periodic oscillations, in good agreement with a recent experiment by Koga [cond-mat/0504743 (unpublished)]. However, our numerical results for the ideal 1D square loop device for the node positions of the amplitudes of the AB and AAS oscillations are found to show some discrepancies with the results for quasi-1D square loops with a finite width. In the presence of disorder and taking the disorder ensemble average, the AB oscillation in the conductance disappears, while the time-reversal symmetric AAS oscillation still remains. Furthermore, the node positions of the AAS oscillatory amplitude remain the same.
Thank You and Farewell to Tonomura-kun
NASA Astrophysics Data System (ADS)
Fukuyama, Hidetoshi
2014-01-01
"Science triggers technology; technology inspires science" is true, so is your case, when you proved partially1 in 1982 and completely2,3 in 1986 the Aharonov-Bohm(AB) effect, the principal manifestation of gauge field, based on the state-of-the-art electron microscope that you developed. You put "period," i.e., an end, on the controversy associated with the AB effect...
Quantum gates with topological phases
Ionicioiu, Radu
2003-09-01
We investigate two models for performing topological quantum gates with the Aharonov-Bohm (AB) and Aharonov-Casher (AC) effects. Topological one- and two-qubit Abelian phases can be enacted with the AB effect using charge qubits, whereas the AC effect can be used to perform all single-qubit gates (Abelian and non-Abelian) for spin qubits. Possible experimental setups suitable for a solid-state implementation are briefly discussed.
Quantum Interference and Surface States Effects in Bismuth Nanowires
NASA Astrophysics Data System (ADS)
Konopko, L.; Huber, T.; Nikolaeva, A.
2010-02-01
We report the observation of Aharonov-Bohm (AB) oscillations for single Bi nanowires with diameter d< 80 nm. The single nanowire samples with glass coating were prepared by the Ulitovsky technique; they were cylindrical single crystals with (10 bar{1} 1) orientation along the wire axis. The surface of Bi nanowire supports surface states which give rise to a significant population of charge carriers with high effective mass that form a highly conducting tube around the nanowire. The oscillations of longitudinal magnetoresistance (MR) of Bi nanowires with two periods Δ B 1 and Δ B 2 proportional to Φ0 and Φ0/2 were observed, where Φ0= h/ e is the flux quantum. From B˜ 8 T down to B = 0 the extremums of Φ0/2 oscillations are shifted up to 3 π at B = 0 which is the manifestation of Berry phase shift due to electron moving in a nonuniform magnetic field. A derivative of MR was measured at various inclined angles. The observed angle variation of the periods is not in agreement with the theoretical dependence Δ( α)=Δ(0)/cos α of the size effect oscillations of the “flux quantization” type. Moreover, the equidistant oscillations of MR exist in transverse magnetic fields under certain rotation angles. An interpretation of the MR oscillations is presented.
Competition of phase-breaking and thermal broadening in few-mode mesoscopic rings
NASA Astrophysics Data System (ADS)
Espe Hansen, Adam; Kristensen, Anders; Pedersen, Simon; Sorensen, Claus; Lindelof, Poul Erik
2001-03-01
The electron phase coherence length L_φ is measured in a ballistic few-mode ring interferometer. For the first time, it is demonstrated that the phase-breaking rate of the n'th harmonic h/ne of the Aharonov-Bohm (AB) magnetoconductance oscillations depends on temperature T like n\\cdot L/L_φ(T), hence scales with the actual pathlength n\\cdot L. Here L is half the ring circumference. To obtain this result, it is necessary to account for the effect of thermal broadening, which depends on the phase-shifts of the AB oscillations. The even harmonics h/2ne are found to be less affected by thermal broadening than the odd harmonics h/(2n+1)e, which can be understood in terms of a simple argument, resembling the argument explaining the h/2e Aharonov-Altshuler-Spivak oscillations in disordered systems. The rings are fabricated by shallow wet-etching in GaAs/GaAlAs heterostructures. The phase coherence length is found to vary as T-1 in the temperature regime from 0.3 K to 4 K, and is estimated to be of the order of 30 μ m at T = 0.3 K.
Karpuskiene, R. . E-mail: karra@itpa.lt; Bogdanovich, P.; Udris, A.
2005-01-01
Ab initio energy spectra of the ground configuration 2s{sup 2}2p{sup 3} and the excited configurations 2s2p{sup 4}, 2p{sup 5}, 2s{sup 2}2p{sup 2}3s, 2s{sup 2}2p{sup 2}3p, 2s{sup 2}2p{sup 2}3d, 2s2p{sup 3}3s, 2s2p{sup 3}3p, and 2s2p{sup 3}3d of nitrogen-like sulphur S X have been calculated using the configuration interaction method. The wavelengths, oscillator strengths, and the emission transition probabilities from configurations 2s{sup 2}2p{sup 2}3l and 2s2p{sup 3}3l are obtained. The calculated results are compared with the recent experimental data.
Direct observation of the Aharonov-Casher phase.
König, M; Tschetschetkin, A; Hankiewicz, E M; Sinova, Jairo; Hock, V; Daumer, V; Schäfer, M; Becker, C R; Buhmann, H; Molenkamp, L W
2006-02-24
Ring structures fabricated from HgTe/HgCdTe quantum wells have been used to study Aharonov-Bohm type conductance oscillations as a function of Rashba spin-orbit splitting strength. We observe nonmonotonic phase changes indicating that an additional phase factor modifies the electron wave function. We associate these observations with the Aharonov-Casher effect. This is confirmed by comparison with numerical calculations of the magnetoconductance for a multichannel ring structure within the Landauer-Büttiker formalism.
Quantum phenomena in transport measurements of topological insulator nanostructures (Review Article)
NASA Astrophysics Data System (ADS)
Fang, Lei; Kwok, Wai-Kwong
2014-04-01
We review the recent experimental advances on quantum phenomena in transport measurements of topological insulators with emphasis on quantum oscillation, weak antilocalization and Aharonov-Bohm effect and Altshuler-Aronov-Spivak effect. Following a brief introduction on the topic, we discuss the identification of the topological surface state based on quantum phenomena. Research prospect of topological insulators is described at the end of this article.
Measurement of the transmission phase of an electron in a quantum two-path interferometer
Takada, S. Watanabe, K.; Yamamoto, M.; Bäuerle, C.; Ludwig, A.; Wieck, A. D.; Tarucha, S.
2015-08-10
A quantum two-path interferometer allows for direct measurement of the transmission phase shift of an electron, providing useful information on coherent scattering problems. In mesoscopic systems, however, the two-path interference is easily smeared by contributions from other paths, and this makes it difficult to observe the true transmission phase shift. To eliminate this problem, multi-terminal Aharonov-Bohm (AB) interferometers have been used to derive the phase shift by assuming that the relative phase shift of the electrons between the two paths is simply obtained when a smooth shift of the AB oscillations is observed. Nevertheless, the phase shifts using such a criterion have sometimes been inconsistent with theory. On the other hand, we have used an AB ring contacted to tunnel-coupled wires and acquired the phase shift consistent with theory when the two output currents through the coupled wires oscillate with well-defined anti-phase. Here, we investigate thoroughly these two criteria used to ensure a reliable phase measurement, the anti-phase relation of the two output currents, and the smooth phase shift in the AB oscillation. We confirm that the well-defined anti-phase relation ensures a correct phase measurement with a quantum two-path interference. In contrast, we find that even in a situation where the anti-phase relation is less well-defined, the smooth phase shift in the AB oscillation can still occur but does not give the correct transmission phase due to contributions from multiple paths. This indicates that the phase relation of the two output currents in our interferometer gives a good criterion for the measurement of the true transmission phase, while the smooth phase shift in the AB oscillation itself does not.
NASA Astrophysics Data System (ADS)
Belyayev, S. T.
2013-06-01
In 1947 I became a second-year student at Moscow State University's Physics and Engineering Department, where a part of the week's classes were taught at base organizations. Our group's base was the future Kurchatov Institute, at that time known as the mysterious "Laboratory N^circ 2," and later as LIPAN.
NASA Astrophysics Data System (ADS)
de Lima, A. G.; Belich, H.; Bakke, K.
2016-10-01
From the effects of the Lorentz symmetry violation in the CPT-even gauge sector of the Standard Model Extension determined by a tensor background (KF)μναβ, we establish a possible scenario where an analogue of the He-McKellar-Wilkens effect can stem from. Besides, we build quantum holonomies associated with the analogue of the He-McKellar-Wilkens effect and discuss a possible analogy with the geometric quantum computation. Finally, we investigate the dependence of the energy levels on the He-McKellar-Wilkens geometric phase induced by Lorentz symmetry breaking effects when the particle is confined to a hard-wall confining potential.
NASA Astrophysics Data System (ADS)
Sarkar, Daipayan
The objective of this research is to understand the temperature variation in dielectric materials of different geometry. The work is divided into three major segments. The Thermal Wave model has been taken into consideration as the classical Fourier law of heat conduction breaks down when a dielectric material of sub-micron geometry is heated rapidly. The first part of the work discusses primarily about the temperature distribution in a semi-infinite dielectric material, followed by the temperature profile in a finite body (plate) and finally mathematical formulation is presented for a two-layered body. The thermal wave equation is used because in dielectric materials the lag time due to temperature (taut) is much less than the lag time due to heat flux (tauq), ( taut <
Dimensional Crossover in Quantum Networks: From Macroscopic to Mesoscopic Physics
NASA Astrophysics Data System (ADS)
Schopfer, Félicien; Mallet, François; Mailly, Dominique; Texier, Christophe; Montambaux, Gilles; Bäuerle, Christopher; Saminadayar, Laurent
2007-01-01
We report on magnetoconductance measurements of metallic networks of various sizes ranging from 10 to 106 plaquettes, with an anisotropic aspect ratio. Both Altshuler-Aronov-Spivak h/2e periodic oscillations and Aharonov-Bohm h/e periodic oscillations are observed for all networks. For large samples, the amplitude of both oscillations results from the incoherent superposition of contributions of phase coherent regions. When the transverse size becomes smaller than the phase coherent length Lϕ, one enters a new regime which is phase coherent (mesoscopic) along one direction and macroscopic along the other, leading to a new size dependence of the quantum oscillations.
Quantum-ring spin interference device tuned by quantum point contacts
NASA Astrophysics Data System (ADS)
Diago-Cisneros, Leo; Mireles, Francisco
2013-11-01
We introduce a spin-interference device that comprises a quantum ring (QR) with three embedded quantum point contacts (QPCs) and study theoretically its spin transport properties in the presence of Rashba spin-orbit interaction. Two of the QPCs conform the lead-to-ring junctions while a third one is placed symmetrically in the upper arm of the QR. Using an appropriate scattering model for the QPCs and the S-matrix scattering approach, we analyze the role of the QPCs on the Aharonov-Bohm (AB) and Aharonov-Casher (AC) conductance oscillations of the QR-device. Exact formulas are obtained for the spin-resolved conductances of the QR-device as a function of the confinement of the QPCs and the AB/AC phases. Conditions for the appearance of resonances and anti-resonances in the spin-conductance are derived and discussed. We predict very distinctive variations of the QR-conductance oscillations not seen in previous QR proposals. In particular, we find that the interference pattern in the QR can be manipulated to a large extend by varying electrically the lead-to-ring topological parameters. The latter can be used to modulate the AB and AC phases by applying gate voltage only. We have shown also that the conductance oscillations exhibits a crossover to well-defined resonances as the lateral QPC confinement strength is increased, mapping the eigenenergies of the QR. In addition, unique features of the conductance arise by varying the aperture of the upper-arm QPC and the Rashba spin-orbit coupling. Our results may be of relevance for promising spin-orbitronics devices based on quantum interference mechanisms.
Quantum-ring spin interference device tuned by quantum point contacts
Diago-Cisneros, Leo; Mireles, Francisco
2013-11-21
We introduce a spin-interference device that comprises a quantum ring (QR) with three embedded quantum point contacts (QPCs) and study theoretically its spin transport properties in the presence of Rashba spin-orbit interaction. Two of the QPCs conform the lead-to-ring junctions while a third one is placed symmetrically in the upper arm of the QR. Using an appropriate scattering model for the QPCs and the S-matrix scattering approach, we analyze the role of the QPCs on the Aharonov-Bohm (AB) and Aharonov-Casher (AC) conductance oscillations of the QR-device. Exact formulas are obtained for the spin-resolved conductances of the QR-device as a function of the confinement of the QPCs and the AB/AC phases. Conditions for the appearance of resonances and anti-resonances in the spin-conductance are derived and discussed. We predict very distinctive variations of the QR-conductance oscillations not seen in previous QR proposals. In particular, we find that the interference pattern in the QR can be manipulated to a large extend by varying electrically the lead-to-ring topological parameters. The latter can be used to modulate the AB and AC phases by applying gate voltage only. We have shown also that the conductance oscillations exhibits a crossover to well-defined resonances as the lateral QPC confinement strength is increased, mapping the eigenenergies of the QR. In addition, unique features of the conductance arise by varying the aperture of the upper-arm QPC and the Rashba spin-orbit coupling. Our results may be of relevance for promising spin-orbitronics devices based on quantum interference mechanisms.
The Electromagnetic Duality Formulation of Geometric Phases
NASA Astrophysics Data System (ADS)
Zhang, Yuchao; Li, Kang
2015-06-01
This paper focuses on the electromagnetic(EM) duality formulation of geometric phases of Aharonov-Bohm(A-B) effect and Aharonov-Casher(A-C) effect. Through the two four-vector potential formulation of electromagnetic theory, we construct a EM duality formulation for both A-B effect and A-C effect. The He-McKellar-Wilkens(HMW) effect is included as a EM duality counterpart of the A-C effect, and also the EM duality counterpart of the A-B effect is also predicted.
An experimental proposal to test the physical effect of the vector potential.
Wang, Rui-Feng
2016-01-29
There are two interpretations of the Aharonov-Bohm (A-B) effect. One interpretation asserts that the A-B effect demonstrates that the vector potential is a physical reality that can result in the phase shift of a moving charge in quantum mechanics. The other interpretation asserts that the phase shift of the moving charge results from the interaction energy between the electromagnetic field of the moving charge and external electromagnetic fields. This paper briefly reviews these two interpretations and analyzes their differences. In addition, a new experimental scheme is proposed to determine which interpretation is correct.
NASA Technical Reports Server (NTRS)
Espinosa, Ismael; Gonzalez, Hortensia; Quiza, Jorge; Gonazalez, J. Jesus; Arroyo, Ruben; Lara, Ritaluz
1995-01-01
Oscillation of electrical activity has been found in many nervous systems, from invertebrates to vertebrates including man. There exists experimental evidence of very simple circuits with the capability of oscillation. Neurons with intrinsic oscillation have been found and also neural circuits where oscillation is a property of the network. These two types of oscillations coexist in many instances. It is nowadays hypothesized that behind synchronization and oscillation there is a system of coupled oscillators responsible for activities that range from locomotion and feature binding in vision to control of sleep and circadian rhythms. The huge knowledge that has been acquired on oscillators from the times of Lord Rayleigh has made the simulation of neural oscillators a very active endeavor. This has been enhanced with more recent physiological findings about small neural circuits by means of intracellular and extracellular recordings as well as imaging methods. The future of this interdisciplinary field looks very promising; some researchers are going into quantum mechanics with the idea of trying to provide a quantum description of the brain. In this work we describe some simulations using neuron models by means of which we form simple neural networks that have the capability of oscillation. We analyze the oscillatory activity with root locus method, cross-correlation histograms, and phase planes. In the more complicated neural network models there is the possibility of chaotic oscillatory activity and we study that by means of Lyapunov exponents. The companion paper shows an example of that kind.
Altshuler-Aronov-Spivak Oscillation in Graphene Antidot lattice
NASA Astrophysics Data System (ADS)
Yagi, Ryuta; Sakakibara, Ryoji; Onishi, Junpei; Yagi Lab. Team
2015-03-01
We have observed the Altshuler-Aronov-Spivac (AAS) oscillation in triangular antidot lattice of single layer graphene. Low temperature magnetoresistance exhibited h / 2 e periodic oscillations near zero magnetic field, negative magnetoresistance, and h / e periodic (AB-type) oscillations at higher magnetic fields. Phase of the AAS oscillation was the same as those for conventional 2D electrons with negligible spin orbit interaction, showing that inter-valley scattering averaged the Berry phase effect which results in anti-localization.
Magnetic Flux Effect on a Kondo-Induced Electric Polarization in a Triangular Triple Quantum Dot
NASA Astrophysics Data System (ADS)
Koga, Mikito; Matsumoto, Masashige; Kusunose, Hiroaki
2014-08-01
A magnetic flux effect is studied theoretically on an electric polarization induced by the Kondo effect in a triangular triple-quantum-dot system, where one of the three dots is connected to a metallic lead. This electric polarization exhibits an Aharonov-Bohm oscillation as a function of the magnetic flux penetrating through the triangular loop. The numerical renormalization group analysis reveals how the oscillation pattern depends on the Kondo coupling of a local spin with lead electrons, which is sensitive to the point contact with the lead. It provides an experimental implication that the Kondo effect is the origin of the emergent electric polarization.
Aharonov-casher effect in Bi2Se3 square-ring interferometers.
Qu, Fanming; Yang, Fan; Chen, Jun; Shen, Jie; Ding, Yue; Lu, Jiangbo; Song, Yuanjun; Yang, Huaixin; Liu, Guangtong; Fan, Jie; Li, Yongqing; Ji, Zhongqing; Yang, Changli; Lu, Li
2011-07-01
Electrical control of spin dynamics in Bi(2)Se(3) was investigated in ring-type interferometers. Aharonov-Bohm and Altshuler-Aronov-Spivak resistance oscillations against a magnetic field, and Aharonov-Casher resistance oscillations against the gate voltage were observed in the presence of a Berry phase of π. A very large tunability of spin precession angle by the gate voltage has been obtained, indicating that Bi(2)Se(3)-related materials with strong spin-orbit coupling are promising candidates for constructing novel spintronic devices.
Surface state dominated transport in topological insulator Bi{sub 2}Te{sub 3} nanowires
Hamdou, Bacel Gooth, Johannes; Dorn, August; Nielsch, Kornelius; Pippel, Eckhard
2013-11-04
We report on low temperature magnetoresistance measurements on single-crystalline Bi{sub 2}Te{sub 3} nanowires synthesized via catalytic growth and post-annealing in a Te-rich atmosphere. The observation of Aharonov-Bohm oscillations indicates the presence of topological surface states. Analyses of Subnikov-de Haas oscillations in perpendicular magnetoresistance yield extremely low two-dimensional carrier concentrations and effective electron masses, and very high carrier mobilities. All our findings are in excellent agreement with theoretical predictions of massless Dirac fermions at the surfaces of topological insulators.
Quantum Electronic Transport of Topological Surface States in β-Ag2Se Nanowire.
Kim, Jihwan; Hwang, Ahreum; Lee, Sang-Hoon; Jhi, Seung-Hoon; Lee, Sunghun; Park, Yun Chang; Kim, Si-In; Kim, Hong-Seok; Doh, Yong-Joo; Kim, Jinhee; Kim, Bongsoo
2016-04-26
Single-crystalline β-Ag2Se nanostructures, a new class of 3D topological insulators (TIs), were synthesized using the chemical vapor transport method. The topological surface states were verified by measuring electronic transport properties including the weak antilocalization effect, Aharonov-Bohm oscillations, and Shubnikov-de Haas oscillations. First-principles band calculations revealed that the band inversion in β-Ag2Se is caused by strong spin-orbit coupling and Ag-Se bonding hybridization. These investigations provide evidence of nontrivial surface state about β-Ag2Se TIs that have anisotropic Dirac cones.
Aharonov-Casher Effect in Bi2Se3 Square-Ring Interferometers
NASA Astrophysics Data System (ADS)
Qu, Fanming; Yang, Fan; Chen, Jun; Shen, Jie; Ding, Yue; Lu, Jiangbo; Song, Yuanjun; Yang, Huaixin; Liu, Guangtong; Fan, Jie; Li, Yongqing; Ji, Zhongqing; Yang, Changli; Lu, Li
2011-07-01
Electrical control of spin dynamics in Bi2Se3 was investigated in ring-type interferometers. Aharonov-Bohm and Altshuler-Aronov-Spivak resistance oscillations against a magnetic field, and Aharonov-Casher resistance oscillations against the gate voltage were observed in the presence of a Berry phase of π. A very large tunability of spin precession angle by the gate voltage has been obtained, indicating that Bi2Se3-related materials with strong spin-orbit coupling are promising candidates for constructing novel spintronic devices.
NASA Astrophysics Data System (ADS)
Stojetz, B.; Roche, S.; Miko, C.; Triozon, F.; Forró, L.; Strunk, C.
2007-03-01
Magnetotransport measurements in large diameter multiwall carbon nanotubes (20 40 nm) demonstrate the competition of a magnetic-field dependent bandstructure and Altshuler Aronov Spivak oscillations. By means of an efficient capacitive coupling to a backgate electrode, the magnetoconductance oscillations are explored as a function of Fermi level shift. Changing the magnetic field orientation with respect to the tube axis and by ensemble averaging, allows the contributions of different Aharonov Bohm phases to be identified. The results are in qualitative agreement with numerical calculations of the band structure and the conductance.
Relativistic Killingbeck energy states under external magnetic fields
NASA Astrophysics Data System (ADS)
Eshghi, M.; Mehraban, H.; Ikhdair, S. M.
2016-07-01
We address the behavior of the Dirac equation with the Killingbeck radial potential including the external magnetic and Aharonov-Bohm (AB) flux fields. The spin and pseudo-spin symmetries are considered. The correct bound state spectra and their corresponding wave functions are obtained. We seek such a solution using the biconfluent Heun's differential equation method. Further, we give some of our results at the end of this study. Our final results can be reduced to their non-relativistic forms by simply using some appropriate transformations. The spectra, in the spin and pseudo-spin symmetries, are very similar with a slight difference in energy spacing between different states.
Gitsevich, Aleksandr
2001-01-01
An oscillator includes an amplifier having an input and an output, and an impedance transformation network connected between the input of the amplifier and the output of the amplifier, wherein the impedance transformation network is configured to provide suitable positive feedback from the output of the amplifier to the input of the amplifier to initiate and sustain an oscillating condition, and wherein the impedance transformation network is configured to protect the input of the amplifier from a destructive feedback signal. One example of the oscillator is a single active element device capable of providing over 70 watts of power at over 70% efficiency. Various control circuits may be employed to match the driving frequency of the oscillator to a plurality of tuning states of the lamp.
Measurement of Aharonov-Casher effect in a Josephson junction chain
NASA Astrophysics Data System (ADS)
Pop, Ioan Mihai; Lecocq, Florent; Pannetier, Bernard; Buisson, Olivier; Guichard, Wiebke
2011-03-01
We have recently measured the effect of superconducting phase-slips on the ground state of a Josephson junction chain and a rhombi chain. Here we report clear evidence of Aharonov-Casher effect in a chain of Josephson junctions. This phenomenon is the dual of the well known Aharonov-Bohm interference. Using a capacitively coupled gate to the islands of the chain, we induce oscillations of the supercurrent by tuning the polarization charges on the islands. We observe complex interference patterns for different quantum phase slip amplitudes, that we understand quantitatively as Aharonov-Casher vortex interferences. European STREP MIDAS.
Quasiballistic Transport of Dirac Fermions in a Bi2Se3 Nanowire
NASA Astrophysics Data System (ADS)
Dufouleur, J.; Veyrat, L.; Teichgräber, A.; Neuhaus, S.; Nowka, C.; Hampel, S.; Cayssol, J.; Schumann, J.; Eichler, B.; Schmidt, O. G.; Büchner, B.; Giraud, R.
2013-05-01
Quantum coherent transport of surface states in a mesoscopic nanowire of the three-dimensional topological insulator Bi2Se3 is studied in the weak-disorder limit. At very low temperatures, many harmonics are evidenced in the Fourier transform of Aharonov-Bohm oscillations, revealing the long phase coherence length of spin-chiral Dirac fermions. Remarkably, from their exponential temperature dependence, we infer an unusual 1/T power law for the phase coherence length Lφ(T). This decoherence is typical for quasiballistic fermions weakly coupled to their environment.
Luttinger liquid theory of Coulomb drag in mesoscopic rings,(Supported in part by US DOE.)
NASA Astrophysics Data System (ADS)
Shahbazyan, T. V.; Ulloa, S. E.
1997-03-01
We develop a Luttinger liquid theory of the Coulomb drag of persistent currents, flowing in concentric mesoscopic rings, by incorporating non-linear corrections to the electron dispersion relation. We demonstrate that at low temperatures interactions between electrons in different rings generate an additional phase and thus alter the period of Aharonov-Bohm oscillations. The resulting nondissipative(A. G. Rojo and G. D. Mahan, Phys. Rev. Lett. 68) 2074 (1992). drag depends strongly on the relative parity of the electron numbers. We also show that interactions set a new temperature scale below which the linear response theory does not apply at certain values of external flux.
Electron Interference in Hall Effect Measurements on GaAs/InAs Core/Shell Nanowires.
Haas, Fabian; Zellekens, Patrick; Lepsa, Mihail; Rieger, Torsten; Grützmacher, Detlev; Lüth, Hans; Schäpers, Thomas
2017-01-11
We present low-temperature magnetotransport measurements on GaAs/InAs core/shell nanowires contacted by regular source-drain leads as well as laterally attached Hall contacts, which only touch parts of the nanowire sidewalls. Low-temperature measurements between source and drain contacts show typical phase coherent effects, such as universal conductance fluctuations in a magnetic field aligned perpendicularly to the nanowire axis as well as Aharonov-Bohm-type oscillations in a parallel aligned magnetic field. However, the signal between the Hall contacts shows a Hall voltage buildup, when the magnetic field is turned perpendicular to the nanowire axis while current is driven through the wire using the source-drain contacts. At low temperatures, the phase coherent effects measured between source and drain leads are superimposed on the Hall voltage, which can be explained by nonlocal probing of large segments of the nanowire. In addition, the Aharonov-Bohm-type oscillations are also observed in the magnetoconductance at magnetic fields aligned parallel to the nanowire axis, using the laterally contacted leads. This measurement geometry hereby directly corresponds to classical Aharonov-Bohm experiments using planar quantum rings. In addition, the Hall voltage is used to characterize the nanowires in terms of charge carrier concentration and mobility, using temperature- and gate-dependent measurements as well as measurements in tilted magnetic fields. The GaAs/InAs core/shell nanowire used in combination with laterally attached contacts is therefore the ideal system to three-dimensionally combine quantum ring experiments using the cross-sectional plane and Hall experiments using the axial nanowire plane.
Baryogenesis via particle-antiparticle oscillations
Ipek, Seyda; March-Russell, John
2016-06-29
CP violation, which is crucial for producing the baryon asymmetry of the Universe, is enhanced in particle-antiparticle oscillations. We study particle-antiparticle oscillations [of a particle with mass O(100GeV)] with CP violation in the early Universe in the presence of interactions with O(ab-fb) cross sections. We show that if baryon-number-violating interactions exist, a baryon asymmetry can be produced via out-of-equilibrium decays of oscillating particles. As a concrete example we study a U(1)R-symmetric, R-parity-violating supersymmetry model with pseudo-Dirac gauginos, which undergo particle-antiparticle oscillations. Hence, taking bino to be the lightest U(1)_{R}-symmetric particle, and assuming it decays via baryon-number-violating interactions, we show that bino-antibino oscillations can produce the baryon asymmetry of the Universe.
Baryogenesis via particle-antiparticle oscillations
Ipek, Seyda; March-Russell, John
2016-06-29
CP violation, which is crucial for producing the baryon asymmetry of the Universe, is enhanced in particle-antiparticle oscillations. We study particle-antiparticle oscillations [of a particle with mass O(100GeV)] with CP violation in the early Universe in the presence of interactions with O(ab-fb) cross sections. We show that if baryon-number-violating interactions exist, a baryon asymmetry can be produced via out-of-equilibrium decays of oscillating particles. As a concrete example we study a U(1)R-symmetric, R-parity-violating supersymmetry model with pseudo-Dirac gauginos, which undergo particle-antiparticle oscillations. Hence, taking bino to be the lightest U(1)R-symmetric particle, and assuming it decays via baryon-number-violating interactions, we show thatmore » bino-antibino oscillations can produce the baryon asymmetry of the Universe.« less
Miller, Kristen; Hunt, Raegan; Chu, Julie; Meehan, Shane; Stein, Jennifer
2011-10-15
Erythema ab igne is a reticulated, erythematous or hyperpigmented dermatosis that results from chronic and repeated exposure to low levels of infrared radiation. Multiple heat sources have been reported to cause this condition, which include heated reclining chairs, heating pads, hot water bottles, car heaters, electric space heaters, and, more recently, laptop computers. Treatment consists of withdrawing the inciting heat source. Although erythema ab igne carries a good prognosis, it is not necessarily a self-limited diagnosis as patients are at long-term risk of developing subsequent cutaneous malignant conditions, which include squamous cell and merkel-cell carcinomas.
George Neil
2003-05-12
FEL Oscillators have been around since 1977 providing not only a test bed for the physics of Free Electron Lasers and electron/photon interactions but as a workhorse of scientific research. More than 30 FEL oscillators are presently operating around the world spanning a wavelength range from the mm region to the ultraviolet using DC and rf linear accelerators and storage rings as electron sources. The characteristics that have driven the development of these sources are the desire for high peak and average power, high micropulse energies, wavelength tunability, timing flexibility, and wavelengths that are unavailable from more conventional laser sources. Substantial user programs have been performed using such sources encompassing medicine, biology, solid state research, atomic and molecular physics, effects of non-linear fields, surface science, polymer science, pulsed laser vapor deposition, to name just a few.
Jessen, P.L.; Price, H.J.
1958-03-18
This patent relates to sine-wave generators and in particular describes a generator with a novel feedback circuit resulting in improved frequency stability. The generator comprises two triodes having a common cathode circuit connected to oscillate at a frequency and amplitude at which the loop galn of the circutt ls unity, and another pair of triodes having a common cathode circuit arranged as a conventional amplifier. A signal is conducted from the osciliator through a frequency selective network to the amplifier and fed back to the osciliator. The unique feature of the feedback circuit is the amplifier operates in the nonlinear portion of its tube characteristics thereby providing a relatively constant feedback voltage to the oscillator irrespective of the amplitude of its input signal.
NASA Technical Reports Server (NTRS)
Duvall, Thomas
2004-01-01
Oscillations were first detected in the solar photosphere in 1962 by Leighton and students. In 1970 it was calculated that these oscillations, with a period near five minutes, were the manifestations of acoustic waves trapped in the interior. The subsequent measurements of the frequencies of global oscillation modes from the spatio-temporal power spectrum of the waves made possible the refinement of solar interior models. Over the years, increased understanding of the nuclear reaction rates, the opacity, the equation of state, convection, and gravitational settling have resulted. Mass flows shift the frequencies of modes leading to very accurate measurements of the interior rotation as a function of radius and latitude. In recent years, analogues of terrestrial seismology have led to a tomography of the interior, including measurements of global north-south flows and flow and wave speed measurements below features such as sunspots. The future of helioseismology seems bright with the approval of NASA's Solar Dynamics Observatory mission, to be launched in 2008.
Band nonparabolicity effect on spectral properties of quantum ring
NASA Astrophysics Data System (ADS)
García, L. F.; Revinova, S. Yu.; Mikhailov, I. D.
2017-03-01
We study the effect of the non-parabolicity of the conduction band and of the interband mixing, on the Aharonov Bohm oscillations of the energy levels of a volcano-shaped thin layer, made of InAs material and deposited on the GaAs substrate, by using the Kane model. We derive a simple interpolative relationship between geometrical parameters of the layer and the confinement potential governing the in-plane electron's movement, which allows us to separate the non-linear energy confinement problem in a volcano-shaped structure with a special geometry. Our results show that the nonparabolicity of dispersion of the conduction band, given by the Kane formula, conduces to a significant lowering of the charge carriers' energies and their stronger localization inside the ring. On the contrary, the nonparabolicity almost does not change neither the amplitude nor the period of the Aharonov Bohm oscillations. Additionally, we analyze the interplay between the localization and tunneling of the charge carriers, generated by the external magnetic field in structures with radially directed single, double and quadruple valleys.
NASA Technical Reports Server (NTRS)
Popovic, Zorana B.; Kim, Moonil; Rutledge, David B.
1988-01-01
Loading a two-dimensional grid with active devices offers a means of combining the power of solid-state oscillators in the microwave and millimeter-wave range. The grid structure allows a large number of negative resistance devices to be combined. This approach is attractive because the active devices do not require an external locking signal, and the combining is done in free space. In addition, the loaded grid is a planar structure amenable to monolithic integration. Measurements on a 25-MESFET grid at 9.7 GHz show power-combining and frequency-locking without an external locking signal, with an ERP of 37 W. Experimental far-field patterns agree with theoretical results obtained using reciprocity.
Potter, B.M.
1980-05-13
An alien liquid detector employs a monitoring element and an oscillatory electronic circuit for maintaining the temperature of the monitoring element substantially above ambient temperature. The output wave form, eg., frequency of oscillation or wave shape, of the oscillatory circuit depends upon the temperaturedependent electrical characteristic of the monitoring element. A predetermined change in the output waveform allows water to be discriminated from another liquid, eg., oil. Features of the invention employing two thermistors in two oscillatory circuits include positioning one thermistor for contact with water and the other thermistor above the oil-water interface to detect a layer of oil if present. Unique oscillatory circuit arrangements are shown that achieve effective thermistor action with an economy of parts and energizing power. These include an operational amplifier employed in an astable multivibrator circuit, a discrete transistor-powered tank circuit, and use of an integrated circuit chip.
Investigation of Quantum Computing With Laughlin Quasiparticles
2007-12-31
Review B 72, 075342, 1-8 (2005) F.E.Camino, W.Zhou, and V.J.Goldman Aharonov - Bohm electron interferometer in the integer quantum Hall regime Physical...Review B 72, 155313, 1-6 (2005) F.E.Camino, W.Zhou, and V.J.Goldman Aharonov - Bohm Superperiod in a Laughlin Quasiparticle Interferometer Physical...is the number of particles being encircled. This quantization condition explicitly adds the Aharonov - Bohm and the statistical contributions to the
Theoretical Studies of the Lifetime of Metastable H3
1990-11-01
Aharonov - Bohm , MAB, metastable 21 09 lifetimes 19. ABSTRACT (Continue on reverse if necessary and identify by block number) In this report, the major steps...Molecular Aharonov - Bohm (MAB) effect (or Berry’s geometric phase). This effect has a profound influence on both the bound and scattering states of...this surface and the ground state one introduces the Molecular Aharonov - Bohm (MBA) effect 49 - 5 2 which needs special treatment, and since we also want
Oscillating Permanent Magnets.
ERIC Educational Resources Information Center
Michaelis, M. M.; Haines, C. M.
1989-01-01
Describes several ways to partially levitate permanent magnets. Computes field line geometries and oscillation frequencies. Provides several diagrams illustrating the mechanism of the oscillation. (YP)
Laptop induced erythema ab igne.
Nayak, Sudhir U K; Shenoi, Shrutakirthi D; Prabhu, Smitha
2012-03-01
Erythema ab igne is a reticular, pigmented dermatosis caused by prolonged and repeated exposure to infrared radiation that is insufficient to produce a burn. The use of laptop computers has increased manifold in the recent past. Prolonged contact of the laptop with the skin can lead to the development of erythema ab igne. We present a case of erythema ab igne secondary to laptop use in an Indian student.
Arango, Yulieth C; Huang, Liubing; Chen, Chaoyu; Avila, Jose; Asensio, Maria C; Grützmacher, Detlev; Lüth, Hans; Lu, Jia Grace; Schäpers, Thomas
2016-09-01
We report on low-temperature transport and electronic band structure of p-type Sb2Te3 nanowires, grown by chemical vapor deposition. Magnetoresistance measurements unravel quantum interference phenomena, which depend on the cross-sectional dimensions of the nanowires. The observation of periodic Aharonov-Bohm-type oscillations is attributed to transport in topologically protected surface states in the Sb2Te3 nanowires. The study of universal conductance fluctuations demonstrates coherent transport along the Aharonov-Bohm paths encircling the rectangular cross-section of the nanowires. We use nanoscale angle-resolved photoemission spectroscopy on single nanowires (nano-ARPES) to provide direct experimental evidence on the nontrivial topological character of those surface states. The compiled study of the bandstructure and the magnetotransport response unambiguosly points out the presence of topologically protected surface states in the nanowires and their substantial contribution to the quantum transport effects, as well as the hole doping and Fermi velocity among other key issues. The results are consistent with the theoretical description of quantum transport in intrinsically doped quasi-one-dimensional topological insulator nanowires.
NASA Astrophysics Data System (ADS)
Arango, Yulieth C.; Huang, Liubing; Chen, Chaoyu; Avila, Jose; Asensio, Maria C.; Grützmacher, Detlev; Lüth, Hans; Lu, Jia Grace; Schäpers, Thomas
2016-09-01
We report on low-temperature transport and electronic band structure of p-type Sb2Te3 nanowires, grown by chemical vapor deposition. Magnetoresistance measurements unravel quantum interference phenomena, which depend on the cross-sectional dimensions of the nanowires. The observation of periodic Aharonov-Bohm-type oscillations is attributed to transport in topologically protected surface states in the Sb2Te3 nanowires. The study of universal conductance fluctuations demonstrates coherent transport along the Aharonov-Bohm paths encircling the rectangular cross-section of the nanowires. We use nanoscale angle-resolved photoemission spectroscopy on single nanowires (nano-ARPES) to provide direct experimental evidence on the nontrivial topological character of those surface states. The compiled study of the bandstructure and the magnetotransport response unambiguosly points out the presence of topologically protected surface states in the nanowires and their substantial contribution to the quantum transport effects, as well as the hole doping and Fermi velocity among other key issues. The results are consistent with the theoretical description of quantum transport in intrinsically doped quasi-one-dimensional topological insulator nanowires.
Arango, Yulieth C.; Huang, Liubing; Chen, Chaoyu; Avila, Jose; Asensio, Maria C.; Grützmacher, Detlev; Lüth, Hans; Lu, Jia Grace; Schäpers, Thomas
2016-01-01
We report on low-temperature transport and electronic band structure of p-type Sb2Te3 nanowires, grown by chemical vapor deposition. Magnetoresistance measurements unravel quantum interference phenomena, which depend on the cross-sectional dimensions of the nanowires. The observation of periodic Aharonov-Bohm-type oscillations is attributed to transport in topologically protected surface states in the Sb2Te3 nanowires. The study of universal conductance fluctuations demonstrates coherent transport along the Aharonov-Bohm paths encircling the rectangular cross-section of the nanowires. We use nanoscale angle-resolved photoemission spectroscopy on single nanowires (nano-ARPES) to provide direct experimental evidence on the nontrivial topological character of those surface states. The compiled study of the bandstructure and the magnetotransport response unambiguosly points out the presence of topologically protected surface states in the nanowires and their substantial contribution to the quantum transport effects, as well as the hole doping and Fermi velocity among other key issues. The results are consistent with the theoretical description of quantum transport in intrinsically doped quasi-one-dimensional topological insulator nanowires. PMID:27581169
Screening of the Coulomb field in a magnetized electron gas of a quantum cylinder
Eminov, P. A.
2009-05-15
The quantum theory is constructed for screening of the Coulomb field of a point charge in a magnetized electron gas of a quantum cylinder. The asymptotics of the screened potential are calculated for both degenerate and Boltzmann electron gases. It is demonstrated that, in the degenerate case, apart from the known quasi-classical monotonic part, the result contains the quantum oscillating part, which corresponds to Friedel oscillations. The Aharonov-Bohm oscillations of the screened Coulomb interaction of electrons on a cylindrical surface are described analytically. It is shown that the Friedel oscillations can be represented as a superposition of oscillations with different frequencies which are determined by the macroscopic properties of the nanotube.
Chemical oscillator as a generalized Rayleigh oscillator
NASA Astrophysics Data System (ADS)
Ghosh, Shyamolina; Ray, Deb Shankar
2013-10-01
We derive the conditions under which a set of arbitrary two dimensional autonomous kinetic equations can be reduced to the form of a generalized Rayleigh oscillator which admits of limit cycle solution. This is based on a linear transformation of field variables which can be found by inspection of the kinetic equations. We illustrate the scheme with the help of several chemical and bio-chemical oscillator models to show how they can be cast as a generalized Rayleigh oscillator.
Synchronization of genetic oscillators
NASA Astrophysics Data System (ADS)
Zhou, Tianshou; Zhang, Jiajun; Yuan, Zhanjiang; Chen, Luonan
2008-09-01
Synchronization of genetic or cellular oscillators is a central topic in understanding the rhythmicity of living organisms at both molecular and cellular levels. Here, we show how a collective rhythm across a population of genetic oscillators through synchronization-induced intercellular communication is achieved, and how an ensemble of independent genetic oscillators is synchronized by a common noisy signaling molecule. Our main purpose is to elucidate various synchronization mechanisms from the viewpoint of dynamics, by investigating the effects of various biologically plausible couplings, several kinds of noise, and external stimuli. To have a comprehensive understanding on the synchronization of genetic oscillators, we consider three classes of genetic oscillators: smooth oscillators (exhibiting sine-like oscillations), relaxation oscillators (displaying jump dynamics), and stochastic oscillators (noise-induced oscillation). For every class, we further study two cases: with intercellular communication (including phase-attractive and repulsive coupling) and without communication between cells. We find that an ensemble of smooth oscillators has different synchronization phenomena from those in the case of relaxation oscillators, where noise plays a different but key role in synchronization. To show differences in synchronization between them, we make comparisons in many aspects. We also show that a population of genetic stochastic oscillators have their own synchronization mechanisms. In addition, we present interesting phenomena, e.g., for relaxation-type stochastic oscillators coupled to a quorum-sensing mechanism, different noise intensities can induce different periodic motions (i.e., inhomogeneous limit cycles).
Holographic charge oscillations
NASA Astrophysics Data System (ADS)
Blake, Mike; Donos, Aristomenis; Tong, David
2015-04-01
The Reissner-Nordström black hole provides the prototypical description of a holographic system at finite density. We study the response of this system to the presence of a local, charged impurity. Below a critical temperature, the induced charge density, which screens the impurity, exhibits oscillations. These oscillations can be traced to the singularities in the density-density correlation function moving in the complex momentum plane. At finite temperature, the oscillations are very similar to the Friedel oscillations seen in Fermi liquids. However, at zero temperature the oscillations in the black hole background remain exponentially damped, while Friedel oscillations relax to a power-law.
Pantcheva, Mina B.; Kahook, Malik Y.
2010-01-01
Anterior chamber drainage angle surgery, namely trabeculotomy and goniotomy, has been commonly utilized in children for many years. Its’ reported success has ranged between 68% and 100% in infants and young children with congenital glaucoma. However, the long-term success of these procedures has been limited in adults presumably due to the formation of anterior synechiae (AS) in the postoperative phase. Recently, ab interno trabeculectomy with the Trabectome™ has emerged as a novel surgical approach to effectively and selectively remove and ablate the trabecular meshwork and the inner wall of the Schlemm’s canal in an attempt to avoid AS formation or other forms of wound healing with resultant closure of the cleft. This procedure seems to have an appealing safety profile with respect to early hypotony or infection if compared to trabeculectomy or glaucoma drainage device implantation. This might be advantageous in some of the impoverish regions of the Middle East and Africa where patients experience difficulties keeping up with their postoperative visits. It is important to note that no randomized trial comparing the Trabectome to other glaucoma procedures appears to have been published to date. Trabectome surgery is not a panacea, however, and it is associated with early postoperative intraocular pressure spikes that may require additional glaucoma surgery as well as a high incidence of hyphema. Reported results show that postoperative intraocular pressure (IOP) remains, at best, in the mid-teen range making it undesirable in patients with low-target IOP goals. A major advantage of Trabectome surgery is that it does not preclude further glaucoma surgery involving the conjunctiva, such as a trabeculectomy or drainage device implantation. As prospective randomized long-term clinical data become available, we will be better positioned to elucidate the exact role of this technique in the glaucoma surgical armamentarium. PMID:21180426
Autonomous Biological System (ABS) experiments.
MacCallum, T K; Anderson, G A; Poynter, J E; Stodieck, L S; Klaus, D M
1998-12-01
Three space flight experiments have been conducted to test and demonstrate the use of a passively controlled, materially closed, bioregenerative life support system in space. The Autonomous Biological System (ABS) provides an experimental environment for long term growth and breeding of aquatic plants and animals. The ABS is completely materially closed, isolated from human life support systems and cabin atmosphere contaminants, and requires little need for astronaut intervention. Testing of the ABS marked several firsts: the first aquatic angiosperms to be grown in space; the first higher organisms (aquatic invertebrate animals) to complete their life cycles in space; the first completely bioregenerative life support system in space; and, among the first gravitational ecology experiments. As an introduction this paper describes the ABS, its flight performance, advantages and disadvantages.
Saturation in coupled oscillators
NASA Astrophysics Data System (ADS)
Roman, Ahmed; Hanna, James
2015-03-01
We consider a weakly nonlinear system consisting of a resonantly forced oscillator coupled to an unforced oscillator. It has long been known that, for quadratic nonlinearities and a 2:1 resonance between the oscillators, a perturbative solution of the dynamics exhibits a phenomenon known as saturation. At low forcing, the forced oscillator responds, while the unforced oscillator is quiescent. Above a critical value of the forcing, the forced oscillator's steady-state amplitude reaches a plateau, while that of the unforced oscillator increases without bound. We show that, contrary to established folklore, saturation is not unique to quadratically nonlinear systems. We present conditions on the form of the nonlinear couplings and resonance that lead to saturation. Our results elucidate a mechanism for localization or diversion of energy in systems of coupled oscillators, and suggest new approaches for the control or suppression of vibrations in engineered systems.
A realistic quantum capacitance model for quantum Hall edge state based Fabry-Pérot interferometers
NASA Astrophysics Data System (ADS)
Kilicoglu, O.; Eksi, D.; Siddiki, A.
2017-01-01
In this work, the classical and the quantum capacitances are calculated for a Fabry-Pérot interferometer operating in the integer quantized Hall regime. We first consider a rotationally symmetric electrostatic confinement potential and obtain the widths and the spatial distribution of the insulating (incompressible) circular strips using a charge density profile stemming from self-consistent calculations. Modelling the electrical circuit of capacitors composed of metallic gates and incompressible/compressible strips, we investigate the conditions to observe Aharonov-Bohm (quantum mechanical phase dependent) and Coulomb blockade (capacitive coupling dependent) effects reflected in conductance oscillations. In a last step, we solve the Schrödinger and the Poisson equations self-consistently in a numerical manner taking into account realistic experimental geometries. We find that, describing the conductance oscillations either by Aharanov-Bohm or Coulomb blockade strongly depends on sample properties also other than size, therefore, determining the origin of these oscillations requires further experimental and theoretical investigation.
Magnetization of disclinated graphene in nonuniform magnetic field
NASA Astrophysics Data System (ADS)
Roshanzamir-Nikou, M.; Goudarzi, H.
2017-02-01
Two-dimensional disclinated atomic graphene layer in curved space-time is exactly discussed, and the explicit dependence of Landau levels on the topological defect and external magnetic field are obtained in the presence of nonuniform magnetic field. It is worth mentioning that the presence of topological defect reduces the degeneracy of energy levels. The persistent current, magnetization, susceptibility and the magnetoresistance of structure are investigated. It can be shown that the curvature of the conical surface affects the pattern of oscillations of persistent current and, of course, corresponding magnetoresistance. The behavior of the above physical quantities as a function of magnetic flux is explicitly found for various defects. We observe that increasing magnetic field leads to a aperiodic oscillation. The large Aharonov-Bohm flux gives rise to vanish the magnetization oscillations.
Bäßler, Svenja Hamdou, Bacel; Sergelius, Philip; Michel, Ann-Kathrin; Zierold, Robert; Gooth, Johannes; Reith, Heiko; Nielsch, Kornelius
2015-11-02
The geometry of topological insulators (TIs) has a major impact on the magnetoelectric band structure of their surface states. Here, we investigate the surface states of cylindrical TI bismuth telluride selenide nanowires with three different diameters, by parallel and transverse magnetoresistance (MR) measurements. In parallel configuration, we observe Aharonov-Bohm oscillations as well as weak antilocalization, indicating two-dimensional TI surface states. In transverse magnetic fields, we observed MR oscillations that are non-linear against the reciprocal of the magnetic field and thus cannot be explained by two- or three-dimensional states. Instead, our transport data analysis reveals that these MR oscillations are the consequence of one-dimensional edge channels at the nanowire surface that form due to the projection of the external magnetic field on the cylindrically curved surface plane in high magnetic fields. Our observation provides an exotic class of surface states that might be used for electronic and spintronic devices.
A realistic quantum capacitance model for quantum Hall edge state based Fabry-Pérot interferometers.
Kilicoglu, O; Eksi, D; Siddiki, A
2017-01-25
In this work, the classical and the quantum capacitances are calculated for a Fabry-Pérot interferometer operating in the integer quantized Hall regime. We first consider a rotationally symmetric electrostatic confinement potential and obtain the widths and the spatial distribution of the insulating (incompressible) circular strips using a charge density profile stemming from self-consistent calculations. Modelling the electrical circuit of capacitors composed of metallic gates and incompressible/compressible strips, we investigate the conditions to observe Aharonov-Bohm (quantum mechanical phase dependent) and Coulomb blockade (capacitive coupling dependent) effects reflected in conductance oscillations. In a last step, we solve the Schrödinger and the Poisson equations self-consistently in a numerical manner taking into account realistic experimental geometries. We find that, describing the conductance oscillations either by Aharanov-Bohm or Coulomb blockade strongly depends on sample properties also other than size, therefore, determining the origin of these oscillations requires further experimental and theoretical investigation.
Covariant harmonic oscillators and coupled harmonic oscillators
NASA Technical Reports Server (NTRS)
Han, Daesoo; Kim, Young S.; Noz, Marilyn E.
1995-01-01
It is shown that the system of two coupled harmonic oscillators shares the basic symmetry properties with the covariant harmonic oscillator formalism which provides a concise description of the basic features of relativistic hadronic features observed in high-energy laboratories. It is shown also that the coupled oscillator system has the SL(4,r) symmetry in classical mechanics, while the present formulation of quantum mechanics can accommodate only the Sp(4,r) portion of the SL(4,r) symmetry. The possible role of the SL(4,r) symmetry in quantum mechanics is discussed.
Creveling, R.
1957-12-17
S> A shock-excited quartz crystal oscillator is described. The circuit was specifically designed for application in micro-time measuring work to provide an oscillator which immediately goes into oscillation upon receipt of a trigger pulse and abruptly ceases oscillation when a second pulse is received. To achieve the instant action, the crystal has a prestressing voltage applied across it. A monostable multivibrator receives the on and off trigger pulses and discharges a pulse through the crystal to initiate or terminate oscillation instantly.
Nature's Autonomous Oscillators
NASA Technical Reports Server (NTRS)
Mayr, H. G.; Yee, J.-H.; Mayr, M.; Schnetzler, R.
2012-01-01
Nonlinearity is required to produce autonomous oscillations without external time dependent source, and an example is the pendulum clock. The escapement mechanism of the clock imparts an impulse for each swing direction, which keeps the pendulum oscillating at the resonance frequency. Among nature's observed autonomous oscillators, examples are the quasi-biennial oscillation and bimonthly oscillation of the Earth atmosphere, and the 22-year solar oscillation. The oscillations have been simulated in numerical models without external time dependent source, and in Section 2 we summarize the results. Specifically, we shall discuss the nonlinearities that are involved in generating the oscillations, and the processes that produce the periodicities. In biology, insects have flight muscles, which function autonomously with wing frequencies that far exceed the animals' neural capacity; Stretch-activation of muscle contraction is the mechanism that produces the high frequency oscillation of insect flight, discussed in Section 3. The same mechanism is also invoked to explain the functioning of the cardiac muscle. In Section 4, we present a tutorial review of the cardio-vascular system, heart anatomy, and muscle cell physiology, leading up to Starling's Law of the Heart, which supports our notion that the human heart is also a nonlinear oscillator. In Section 5, we offer a broad perspective of the tenuous links between the fluid dynamical oscillators and the human heart physiology.
NASA Technical Reports Server (NTRS)
Phillips, D. H.
1982-01-01
During warmup, crystal oscillators often show a frequency offset as large as 1 part in 10 to the 5th power. If timing information is transferred to the oscillator and then the oscillator is allowed to warmup, a timing error greater than 1 millisecond will occur. For many applications, it is unsuitable to wait for the oscillator to warmup. For medium accuracy timing requirements where overall accuracies in the order of 1 millisecond are required, a no warmup crystal concept was developed. The concept utilizes two crystal oscillator, used sequentially to avoid using a crystal oscillator for timing much higher frequency accuracy once warmed up. The accuracy achieved with practical TCXOs at initial start over a range of temperatures is discussed. A second design utilizing two oven controlled oscillators is also discussed.
NASA Astrophysics Data System (ADS)
Hagedorn, P.
The mathematical pendulum is used to provide a survey of free and forced oscillations in damped and undamped systems. This simple model is employed to present illustrations for and comparisons between the various approximation schemes. A summary of the Liapunov stability theory is provided. The first and the second method of Liapunov are explained for autonomous as well as for nonautonomous systems. Here, a basic familiarity with the theory of linear oscillations is assumed. La Salle's theorem about the stability of invariant domains is explained in terms of illustrative examples. Self-excited oscillations are examined, taking into account such oscillations in mechanical and electrical systems, analytical approximation methods for the computation of self-excited oscillations, analytical criteria for the existence of limit cycles, forced oscillations in self-excited systems, and self-excited oscillations in systems with several degrees of freedom. Attention is given to Hamiltonian systems and an introduction to the theory of optimal control is provided.
Low-temperature magnetoresistance of individual single-walled carbon nanotubes: A numerical study
NASA Astrophysics Data System (ADS)
Zhang, Zhenhua; Peng, Jingcui; Huang, Xiaoyi; Zhang, Hua
2002-08-01
The low-temperature magnetoresistance induced by an axial magnetic field in individual single-walled carbon nanotubes (SWNTs) is studied numerically based on Boltzmann transport equation and π electronic energy dispersion relations for individual SWNTs as well as taking one-dimensional weak localization (WL) into account. It is shown that the Altshuler-Aronov-Spivak effect related to WL is much weaker in individual SWNTs than in individual multiwalled carbon nanotubes, whereas the Aharonov-Bohm (AB) effect related to tubular energy band structure is stronger in individual SWNTs when the conducting electrons occupy lower energy levels, but this effect weakens rapidly as conducting electron energy increases. This suggests that only the AB effect can be observed remarkably in the states of the conducting electrons with lower energy.
Ab Initio and Ab Exitu No-Core Shell Model
Vary, J P; Navratil, P; Gueorguiev, V G; Ormand, W E; Nogga, A; Maris, P; Shirokov, A
2007-10-02
We outline two complementary approaches based on the no core shell model (NCSM) and present recent results. In the ab initio approach, nuclear properties are evaluated with two-nucleon (NN) and three-nucleon interactions (TNI) derived within effective field theory (EFT) based on chiral perturbation theory (ChPT). Fitting two available parameters of the TNI generates good descriptions of light nuclei. In a second effort, an ab exitu approach, results are obtained with a realistic NN interaction derived by inverse scattering theory with off-shell properties tuned to fit light nuclei. Both approaches produce good results for observables sensitive to spin-orbit properties.
Optical analog of the Iordanskii force in a Bose-Einstein condensate
Leonhardt, U.; Oehberg, P.
2003-05-01
A vortex in a Bose-Einstein condensate generates the optical analog of the Aharonov-Bohm effect when illuminated with slow light. In contrast to the original Aharonov-Bohm effect the vortex will exchange forces with the light that leads to a measurable motion of the vortex.
Quantum optics: Photons taught new tricks
NASA Astrophysics Data System (ADS)
Stern, Ady
2016-10-01
Experiments of the Aharonov-Bohm type typically involve particles that are charged and interact with a magnetic flux. Photons aren't the former and don't do the latter. Yet, an Aharonov-Bohm ring for photons has just been realized experimentally.
Paradoxes of neutrino oscillations
Akhmedov, E. Kh.; Smirnov, A. Yu.
2009-08-15
Despite the theory of neutrino oscillations being rather old, some of its basic issues are still being debated in the literature. We discuss a number of such issues, including the relevance of the 'same energy' and 'same momentum' assumptions, the role of quantum-mechanical uncertainty relations in neutrino oscillations, the dependence of the coherence and localization conditions that ensure the observability of neutrino oscillations on neutrino energy and momentum uncertainties, the question of (in)dependence of the oscillation probabilities on the neutrino production and detection processes, and the applicability limits of the stationary-source approximation. We also develop a novel approach to calculation of the oscillation probability in the wave-packet approach, based on the summation/integration conventions different from the standard one, which allows a new insight into the 'same energy' vs. 'same momentum' problem. We also discuss a number of apparently paradoxical features of the theory of neutrino oscillations.
Edge-channel interferometer at the graphene quantum Hall pn junction
Morikawa, Sei; Moriya, Rai; Masubuchi, Satoru Machida, Tomoki; Watanabe, Kenji; Taniguchi, Takashi
2015-05-04
We demonstrate a quantum Hall edge-channel interferometer in a high-quality graphene pn junction under a high magnetic field. The co-propagating p and n quantum Hall edge channels traveling along the pn interface functions as a built-in Aharonov-Bohm-type interferometer, the interferences in which are sensitive to both the external magnetic field and the carrier concentration. The trajectories of peak and dip in the observed resistance oscillation are well reproduced by our numerical calculation that assumes magnetic flux quantization in the area enclosed by the co-propagating edge channels. Coherent nature of the co-propagating edge channels is confirmed by the checkerboard-like pattern in the dc-bias and magnetic-field dependences of the resistance oscillations.
Point-contact spectroscopy of hopping transport : efffects of a magnetic field.
Kozub, V. I.; Zyuzin, A. A.; Entin-Wohlman, O.; Aharony, A.; Galperin, Y. M.; Vinokur, V.; Materials Science Division; Russian Acad. Sci.; Ben Gurion Univ.; Univ. Oslo
2007-01-01
The conductance of a point contact between two hopping insulators is expected to be dominated by the individual localized states in its vicinity. Here, we study the additional effects due to an external magnetic field. Combined with the measured conductance, the measured magnetoresistance provides detailed information on these states (e.g., their localization length, the energy difference, and the hopping distance between them). We also calculate the statistics of this magnetoresistance, which can be collected by changing the gate voltage in a single device. Since the conductance is dominated by the quantum interference of particular mesoscopic structures near the point contact, it is predicted to exhibit Aharonov-Bohm oscillations, which yield information on the geometry of these structures. These oscillations also depend on local spin accumulation and correlations, which can be modified by the external field. Finally, we also estimate the mesoscopic Hall voltage due to these structures.
Conductance maps of quantum rings due to a local potential perturbation
NASA Astrophysics Data System (ADS)
Petrović, M. D.; Peeters, F. M.; Chaves, A.; Farias, G. A.
2013-12-01
We performed a numerical simulation of the dynamics of a Gaussian shaped wavepacket inside a small sized quantum ring, smoothly connected to two leads and exposed to a perturbing potential of a biased atomic force microscope tip. Using the Landauer formalism, we calculated conductance maps of this system in the case of single and two subband transport. We explain the main features in the conductance maps as due to the AFM tip influence on the wavepacket phase and amplitude. In the presence of an external magnetic field, the tip modifies the ϕ0 periodic Aharonov-Bohm oscillation pattern into a ϕ0/2 periodic Al’tshuler-Aronov-Spivak oscillation pattern. Our results in the case of multiband transport suggest tip selectivity to higher subbands, making them more observable in the total conductance map.
Oscillations in stellar atmospheres
NASA Technical Reports Server (NTRS)
Costa, A.; Ringuelet, A. E.; Fontenla, J. M.
1989-01-01
Atmospheric excitation and propagation of oscillations are analyzed for typical pulsating stars. The linear, plane-parallel approach for the pulsating atmosphere gives a local description of the phenomenon. From the local analysis of oscillations, the minimum frequencies are obtained for radially propagating waves. The comparison of the minimum frequencies obtained for a variety of stellar types is in good agreement with the observed periods of the oscillations. The role of the atmosphere in the globar stellar pulsations is thus emphasized.
Workshop on Harmonic Oscillators
NASA Technical Reports Server (NTRS)
Han, D. (Editor); Kim, Y. S. (Editor); Zachary, W. W. (Editor)
1993-01-01
Proceedings of a workshop on Harmonic Oscillators held at the College Park Campus of the University of Maryland on March 25 - 28, 1992 are presented. The harmonic oscillator formalism is playing an important role in many branches of physics. This is the simplest mathematical device which can connect the basic principle of physics with what is observed in the real world. The harmonic oscillator is the bridge between pure and applied physics.
NASA Astrophysics Data System (ADS)
Jenkins, Alejandro
2013-04-01
Physicists are very familiar with forced and parametric resonance, but usually not with self-oscillation, a property of certain dynamical systems that gives rise to a great variety of vibrations, both useful and destructive. In a self-oscillator, the driving force is controlled by the oscillation itself so that it acts in phase with the velocity, causing a negative damping that feeds energy into the vibration: no external rate needs to be adjusted to the resonant frequency. The famous collapse of the Tacoma Narrows bridge in 1940, often attributed by introductory physics texts to forced resonance, was actually a self-oscillation, as was the swaying of the London Millennium Footbridge in 2000. Clocks are self-oscillators, as are bowed and wind musical instruments. The heart is a “relaxation oscillator”, i.e., a non-sinusoidal self-oscillator whose period is determined by sudden, nonlinear switching at thresholds. We review the general criterion that determines whether a linear system can self-oscillate. We then describe the limiting cycles of the simplest nonlinear self-oscillators, as well as the ability of two or more coupled self-oscillators to become spontaneously synchronized (“entrained”). We characterize the operation of motors as self-oscillation and prove a theorem about their limit efficiency, of which Carnot’s theorem for heat engines appears as a special case. We briefly discuss how self-oscillation applies to servomechanisms, Cepheid variable stars, lasers, and the macroeconomic business cycle, among other applications. Our emphasis throughout is on the energetics of self-oscillation, often neglected by the literature on nonlinear dynamical systems.
Registration of nine sorghum seed parent (A/B) lines
Technology Transfer Automated Retrieval System (TEKTRAN)
Nine sorghum [Sorghum bicolor (L.) Moench] A1 cyto plasmic-genic male sterile seed parent (A) and their maintainer (B) lines [KS 133A/B, KS 134A/B, KS 135A/B, KS 136A/B, KS 137A/B, KS 138A/B, KS 139A/B, KS 140A/B and KS 141A/B] were released by the Kansas State University, Agricultural Research Cent...
12 CFR Appendixes A-B - [Reserved
Code of Federal Regulations, 2014 CFR
2014-01-01
... 12 Banks and Banking 6 2014-01-01 2012-01-01 true A Appendixes A-B Banks and Banking OFFICE OF THRIFT SUPERVISION, DEPARTMENT OF THE TREASURY CAPITAL Regulatory Capital Requirements Appendixes A-B...
12 CFR Appendixes A-B - [Reserved
Code of Federal Regulations, 2013 CFR
2013-01-01
... 12 Banks and Banking 6 2013-01-01 2012-01-01 true A Appendixes A-B Banks and Banking OFFICE OF THRIFT SUPERVISION, DEPARTMENT OF THE TREASURY CAPITAL Regulatory Capital Requirements Appendixes A-B...
12 CFR Appendixes A-B - [Reserved
Code of Federal Regulations, 2010 CFR
2010-01-01
... 12 Banks and Banking 5 2010-01-01 2010-01-01 false A Appendixes A-B Banks and Banking OFFICE OF THRIFT SUPERVISION, DEPARTMENT OF THE TREASURY CAPITAL Regulatory Capital Requirements Appendixes A-B...
12 CFR Appendixes A-B - [Reserved
Code of Federal Regulations, 2011 CFR
2011-01-01
... 12 Banks and Banking 5 2011-01-01 2011-01-01 false A Appendixes A-B Banks and Banking OFFICE OF THRIFT SUPERVISION, DEPARTMENT OF THE TREASURY CAPITAL Regulatory Capital Requirements Appendixes A-B...
12 CFR Appendixes A-B - [Reserved
Code of Federal Regulations, 2012 CFR
2012-01-01
... 12 Banks and Banking 6 2012-01-01 2012-01-01 false A Appendixes A-B Banks and Banking OFFICE OF THRIFT SUPERVISION, DEPARTMENT OF THE TREASURY CAPITAL Regulatory Capital Requirements Appendixes A-B...
Electronically Tuned Microwave Oscillator
NASA Technical Reports Server (NTRS)
Lakshminarayana, Mysore
1987-01-01
Features include low phase noise and frequency stability. Bias-tuned, low-phase-noise microwave oscillator circuit based on npn bipolar transistor and dielectric resonator. Operating at frequency of about 8.4 GHz, oscillator adjusted to give low phase noise, relatively flat power output versus frequency, and nearly linear frequency versus bias voltage.
Investigating Magnetic Oscillations.
ERIC Educational Resources Information Center
Brueningsen, Christopher A.
1993-01-01
Studies magnetic oscillation using an air track. Ceramic magnets are attached to the cart and also are used as dampeners in place of the springs. The resulting oscillations are fairly sinusoidal and is a good example of simple harmonic motion. (MVL)
Wessendorf, Kurt O.
2001-01-01
An active bridge oscillator is formed from a differential amplifier where positive feedback is a function of the impedance of one of the gain elements and a relatively low value common emitter resistance. This use of the nonlinear transistor parameter h stabilizes the output and eliminates the need for ALC circuits common to other bridge oscillators.
Dirac bound states of anharmonic oscillator in external fields
Hamzavi, Majid; Ikhdair, Sameer M.; Falaye, Babatunde J.
2014-02-15
We explore the effect of the external magnetic and Aharonov–Bohm (AB) flux fields on the energy levels of Dirac particle subjects to mixed scalar and vector anharmonic oscillator field in the two-dimensional (2D) space. We calculate the exact energy eigenvalues and the corresponding un-normalized two-spinor-components wave functions in terms of the chemical potential parameter, magnetic field strength, AB flux field and magnetic quantum number by using the Nikiforov–Uvarov (NU) method. -- Highlights: • Effect of the external fields on the energy levels of Dirac particle with the anharmonic oscillator is investigated. • The solutions are discussed in view of spin and pseudospin symmetries limits. • The energy levels and wave function are presented by the Nikiforov–Uvarov method.
Singer, S.; Neher, L.K.
1957-09-24
A high powered, radio frequency pulse oscillator is described for generating trains of oscillations at the instant an input direct voltage is impressed, or immediately upon application of a light pulse. In one embodiment, the pulse oscillator comprises a photo-multiplier tube with the cathode connected to the first dynode by means of a resistor, and adjacent dynodes are connected to each other through adjustable resistors. The ohmage of the resistors progressively increases from a very low value for resistors adjacent the cathode to a high value adjacent the plate, the last dynode. Oscillation occurs with this circuit when a high negative voltage pulse is applied to the cathode and the photo cathode is bombarded. Another embodiment adds capacitors at the resistor connection points of the above circuit to increase the duration of the oscillator train.
Oscillators and Oscillations in the Basal Ganglia
Wilson, Charles J.
2015-01-01
What is the meaning of an action potential? There must be different answers for neurons that oscillate spontaneously, firing action potentials even in the absence of any synaptic input, and those driven to fire from a resting membrane potential. In spontaneously firing neurons, the occurrence of the next action potential is guaranteed. Only variations in its timing can carry the message. Among cells of this type are all those making up the deeper nuclei of the basal ganglia, including both segments of the globus pallidus, the substantia nigra, and the subthalamic nucleus. These cells receive thousands of excitatory and inhibitory synaptic inputs, but no input is required to maintain the firing of the cells; they fire at approximately the same rate when the synapses are silenced. Instead, synaptic inputs produce brief changes in spike timing and firing rate. The interactions among oscillating cells within and among the basal ganglia nuclei produce a complex resting pattern of activity. Normally, this pattern is highly irregular and decorrelates the network, so that the firing of each cell is statistically independent of the others. This maximizes the potential information that may be transmitted by the basal ganglia to its target structures. In Parkinson’s disease, the resting pattern of activity is dominated by a slow oscillation shared by all the neurons. Treatment with deep brain stimulation may gain its therapeutic value by disrupting this shared pathological oscillation, and restoring independent action by each neuron in the network. PMID:25449134
Ultrastable Cryogenic Microwave Oscillators
NASA Astrophysics Data System (ADS)
Mann, Anthony G.
Ultrastable cryogenic microwave oscillators are secondary frequency standards in the microwave domain. The best of these oscillators have demonstrated a short term frequency stability in the range 10-14 to a few times 10-16. The main application for these oscillators is as flywheel oscillators for the next generation of passive atomic frequency standards, and as local oscillators in space telemetry ground stations to clean up the transmitter close in phase noise. Fractional frequency stabilities of passive atomic frequency standards are now approaching 3 x10^-14 /τ where τ is the measurement time, limited only by the number of atoms that are being interrogated. This requires an interrogation oscillator whose short-term stability is of the order of 10-14 or better, which cannot be provided by present-day quartz technology. Ultrastable cryogenic microwave oscillators are based on resonators which have very high electrical Q-factors. The resolution of the resonator's linewidth is typically limited by electronics noise to about 1ppm and hence Q-factors in excess of 108 are required. As these are only attained in superconducting cavities or sapphire resonators at low temperatures, use of liquid helium cooling is mandatory, which has so far restricted these oscillators to the research or metrology laboratory. Recently, there has been an effort to dispense with the need for liquid helium and make compact flywheel oscillators for the new generation of primary frequency standards. Work is under way to achieve this goal in space-borne and mobile liquid-nitrogen-cooled systems. The best cryogenic oscillators developed to date are the ``whispering gallery'' (WG) mode sapphire resonator-oscillators of NASA's Jet Propulsion Laboratory (JPL) and the University of Western Australia (UWA), as well as Stanford University's superconducting cavity stabilized oscillator (SCSO). All of these oscillators have demonstrated frequency
NASA Astrophysics Data System (ADS)
Gavrilik, A. M.; Kachurik, I. I.; Rebesh, A. P.
2010-06-01
We study the properties of the sequences of the energy eigenvalues for some generalizations of q-deformed oscillators including the p, q-oscillator, and the three-, four- and five-parameter deformed oscillators given in the literature. It is shown that most of the considered models belong to the class of so-called Fibonacci oscillators for which any three consecutive energy levels satisfy the relation En + 1 = λEn + ρEn - 1 with real constants λ, ρ. On the other hand, for a certain μ-oscillator known since 1993, we prove its non-Fibonacci nature. Possible generalizations of the three-term Fibonacci relation are discussed, among which for the μ-oscillator we choose, as the most adequate, the so-called quasi-Fibonacci (or local Fibonacci) property of the energy levels. The property is encoded in the three-term quasi-Fibonacci (QF) relation with the non-constant, n-dependent coefficients λ and ρ. Various aspects of the QF relation are elaborated for the μ-oscillator and some of its extensions.
Undamped fritting oscillations
NASA Astrophysics Data System (ADS)
Titov, V. A.
2013-01-01
Fritting oscillations in a glasslike film of methane and chlorine rapidly attenuate. A change in the boundary condition makes them weakly damped, while dosed synchronized injections of vacancies with high-energy particles make it possible to obtain a self-oscillatory system. The mechanism of fritting oscillations is described in detail. An oscillating dissipative structure is formed in the active medium of nonequilibrium glass supersaturated with vacancies and exhibiting a liquid-like behavior. A capillary flow of the medium plays a special role in its evolution.
Solar atmosphere neutrino oscillations
Fogli, G.L.; Lisi, E.; Mirizzi, A.; Montanino, D.; Serpico, P.D.; /Fermilab
2007-02-01
The Sun is a source of high energy neutrinos (E > 10 GeV) produced by cosmic ray interactions in the solar atmosphere. We study the impact of three-flavor oscillations on the solar atmosphere neutrino fluxes observable at Earth. We find that peculiar matter oscillation effects in the Sun do exist, but are significantly suppressed by averaging over the production region and over the neutrino and antineutrino components. In particular, the relation between the neutrino fluxes at the Sun and at the Earth can be approximately expressed in terms of phase-averaged ''vacuum'' oscillations, dominated by a single mixing parameter (the angle {theta}{sub 23}).
LSND neutrino oscillation results
Louis, W.C.
1996-06-01
In the past several years, a number of experiments have searched for neutrino oscillations, where a neutrino of one type (say {bar {nu}}{sub {mu}}) spontaneously transforms into a neutrino of another type (say {bar {nu}}{sub e}). For this phenomenon to occur, neutrinos must be massive and the apparent conservation law of lepton families must be violated. In 1995 the LSND experiment published data showing candidate events that are consistent with {bar {nu}}{sub {mu}} oscillations. Additional data are reported here which provide stronger evidence for neutrino oscillations.
Effect of a cosmic string on spin dynamics
NASA Astrophysics Data System (ADS)
Chowdhury, Debashree; Basu, B.
2014-12-01
In the present paper, we have investigated the role of the cosmic string on spin current and Hall electric field. Due to the background cosmic string, the modified electric field of the system generates renormalized spin-orbit coupling, which induces a modified non-Abelian gauge field. The defect causes a change in the Aharonov-Bohm and Aharonov-Casher phases appearing due to the modified electromagnetic field. In addition, for a time varying electric field we perform explicit analytic calculations to derive the exact form of spin electric field and spin current, which is defect parameter dependent and of oscillating type. Furthermore, in an asymmetric crystal within the Drude model approach we investigate the dependence of the cosmic string parameters on cosmic string induced Hall electric field.
Electronic and optical properties of core-shell nanowires in a magnetic field.
Ravi Kishore, V V; Partoens, B; Peeters, F M
2014-03-05
The electronic and optical properties of zincblende nanowires are investigated in the presence of a uniform magnetic field directed along the [001] growth direction within the k · p method. We focus our numerical study on core-shell nanowires consisting of the III-V materials GaAs, Al(x)Ga(1-x)As and (Al(y)Ga(1-y))₀.₅₁In₀.₄₉P. Nanowires with electrons confined in the core exhibit a Fock-Darwin-like spectrum, whereas nanowires with electrons confined in the shell show Aharonov-Bohm oscillations. Thus, by properly choosing the core and the shell materials of the nanowire, the optical properties in a magnetic field can be tuned in very different ways.
Quantum operations: technical or fundamental challenge?
NASA Astrophysics Data System (ADS)
Mielnik, Bogdan
2013-09-01
A class of unitary operations generated by idealized, semiclassical fields is studied. The operations implemented by sharp potential kicks are revisited and the possibility of performing them by softly varying external fields is examined. The possibility of using the ion traps as ‘operation factories’ transforming quantum states is discussed. The non-perturbative algorithms indicate that the results of abstract δ-pulses of oscillator potentials can become real. Some of them, if empirically achieved, could be essential to examine certain atypical quantum ideas. In particular, simple dynamical manipulations might contribute to the Aharonov-Bohm criticism of the time-energy uncertainty principle, while some others may verify the existence of fundamental precision limits of the position measurements or the reality of ‘non-commutative geometries’.
Omidi, Mahboubeh Faizabadi, Edris
2015-03-21
Magnetic susceptibility is investigated in a man-made elliptical quantum ring in the presence of Rashba spin-orbit interactions and the magnetic flux. It is shown that magnetic susceptibility as a function of magnetic flux changes between negative and positive signs periodically. The periodicity of the Aharonov-Bohm oscillations depends on the geometry of the region where magnetic field is applied, the eccentricity, and number of sites in each chain ring (the elliptical ring is composed of chain rings). The magnetic susceptibility sign can be reversed by tuning the Rashba spin-orbit strength as well. Both the magnetic susceptibility strength and sign can be controlled via external spin-orbit interactions, which can be exploited in spintronics and nanoelectronics.
NASA Astrophysics Data System (ADS)
Omidi, Mahboubeh; Faizabadi, Edris
2015-09-01
We use a simple model to study the electron-phonon interaction influences on persistent current in a one-dimensional quantum ring enclosed by a magnetic flux. With increasing the temperature, persistent current amplitude is reduced, especially in a quantum ring with two ions per primitive cell (diatomic ring) because of the participation of optical phonons. Furthermore, the periodicity of the Aharonov-Bohm oscillations changes to Φ0 / 2 (Φ0 is magnetic flux quantum). In a diatomic ring, by increasing the difference between left and right nearest-neighbor hopping integrals at zero temperature, persistent current variations show a transition from metallic to insulator against distinctive behavior at nonzero temperature.
Transport of Massless Dirac Fermions in Non-topological Type Edge States
Latyshev, Yu I.; Orlov, A. P.; Volkov, V. A.; Enaldiev, V. V.; Zagorodnev, I. V.; Vyvenko, O. F.; Petrov, Yu V.; Monceau, P.
2014-01-01
There are two types of intrinsic surface states in solids. The first type is formed on the surface of topological insulators. Recently, transport of massless Dirac fermions in the band of “topological” states has been demonstrated. States of the second type were predicted by Tamm and Shockley long ago. They do not have a topological background and are therefore strongly dependent on the properties of the surface. We study the problem of the conductivity of Tamm-Shockley edge states through direct transport experiments. Aharonov-Bohm magneto-oscillations of resistance are found on graphene samples that contain a single nanohole. The effect is explained by the conductivity of the massless Dirac fermions in the edge states cycling around the nanohole. The results demonstrate the deep connection between topological and non-topological edge states in 2D systems of massless Dirac fermions. PMID:25524881
Quantum Phase Coherence in Mesoscopic Transport Devices with Two-Particle Interaction
Wang, Zhimei; Guo, Xiaofang; Xue, Haibin; Xue, Naitao; Liang, J.-Q.
2015-01-01
In this paper we demonstrate a new type of quantum phase coherence (QPC), which is generated by the two-body interaction. This conclusion is based on quantum master equation analysis for the full counting statistics of electron transport through two parallel quantum-dots with antiparallel magnetic fluxes in order to eliminate the Aharonov-Bohm interference of either single-particle or non-interacting two-particle wave functions. The interacting two-particle QPC is realized by the flux-dependent oscillation of the zero-frequency cumulants including the shot noise and skewness with a characteristic period. The accurately quantized peaks of cumulant spectrum may have technical applications to probe the two-body Coulomb interaction. PMID:26255858
Decoherence of high-energy electrons in weakly disordered quantum Hall edge states
NASA Astrophysics Data System (ADS)
Nigg, Simon E.; Lunde, Anders Mathias
2016-07-01
We investigate theoretically the phase coherence of electron transport in edge states of the integer quantum Hall effect at filling factor ν =2 , in the presence of disorder and inter edge state Coulomb interaction. Within a Fokker-Planck approach, we calculate analytically the visibility of the Aharonov-Bohm oscillations of the current through an electronic Mach-Zehnder interferometer. In agreement with recent experiments, we find that the visibility is independent of the energy of the current-carrying electrons injected high above the Fermi sea. Instead, it is the amount of disorder at the edge that sets the phase space available for inter edge state energy exchange and thereby controls the visibility suppression.
NASA Astrophysics Data System (ADS)
Zhao, Hong-Kang; Wang, Jian; Wang, Qing
2014-04-01
The shot noise of a hybrid triple-quantum-dot (TQD) interferometer has been investigated by employing the nonequilibrium Green's function method, and the general shot noise formula has been derived. The oscillation behaviors of transmission coefficients and shot noise versus the Aharonov-Bohm phase ϕ exhibit asymmetric Fano resonance structure and blockade effect. Sub-Poissonian and super-Poissonian behaviors of shot noise appear in different regimes of terminal bias eVγ contributed by the Andreev reflection, and correlation of Andreev tunneling with the normal electron transport. The inverse resonance and resonance structures emerge in the shot noise and Fano factor with respect to one of the gate voltages in different regimes of eVγ. The asymmetric structure can be enhanced by modifying the energy levels and gate biases of the TQD. The self-correlation and cross-correlation of current components contribute to the enhancement and suppression of shot noise.
Entraining synthetic genetic oscillators
NASA Astrophysics Data System (ADS)
Wagemakers, Alexandre; Buldú, Javier M.; Sanjuán, Miguel A. F.; de Luis, Oscar; Izquierdo, Adriana; Coloma, Antonio
2009-09-01
We propose a new approach for synchronizing a population of synthetic genetic oscillators, which consists in the entrainment of a colony of repressilators by external modulation. We present a model where the repressilator dynamics is affected by periodic changes in temperature. We introduce an additional plasmid in the bacteria in order to correlate the temperature variations with the enhancement of the transcription rate of a certain gene. This can be done by introducing a promoter that is related to the heat shock response. This way, the expression of that gene results in a protein that enhances the overall oscillations. Numerical results show coherent oscillations of the population for a certain range of the external frequency, which is in turn related to the natural oscillation frequency of the modified repressilator. Finally we study the transient times related with the loss of synchronization and we discuss possible applications in biotechnology of large-scale production coupled to synchronization events induced by heat shock.
Oscillating fluid power generator
Morris, David C
2014-02-25
A system and method for harvesting the kinetic energy of a fluid flow for power generation with a vertically oriented, aerodynamic wing structure comprising one or more airfoil elements pivotably attached to a mast. When activated by the moving fluid stream, the wing structure oscillates back and forth, generating lift first in one direction then in the opposite direction. This oscillating movement is converted to unidirectional rotational movement in order to provide motive power to an electricity generator. Unlike other oscillating devices, this device is designed to harvest the maximum aerodynamic lift forces available for a given oscillation cycle. Because the system is not subjected to the same intense forces and stresses as turbine systems, it can be constructed less expensively, reducing the cost of electricity generation. The system can be grouped in more compact clusters, be less evident in the landscape, and present reduced risk to avian species.
High frequency nanotube oscillator
Peng, Haibing [Houston, TX; Zettl, Alexander K [Kensington, TX
2012-02-21
A tunable nanostructure such as a nanotube is used to make an electromechanical oscillator. The mechanically oscillating nanotube can be provided with inertial clamps in the form of metal beads. The metal beads serve to clamp the nanotube so that the fundamental resonance frequency is in the microwave range, i.e., greater than at least 1 GHz, and up to 4 GHz and beyond. An electric current can be run through the nanotube to cause the metal beads to move along the nanotube and changing the length of the intervening nanotube segments. The oscillator can operate at ambient temperature and in air without significant loss of resonance quality. The nanotube is can be fabricated in a semiconductor style process and the device can be provided with source, drain, and gate electrodes, which may be connected to appropriate circuitry for driving and measuring the oscillation. Novel driving and measuring circuits are also disclosed.
NASA Technical Reports Server (NTRS)
Yao, X. S.; Maleki, L.
1995-01-01
We report a novel oscillator for photonic RF systems. This oscillator is capable of generating high-frequency signals up to 70 GHz in both electrical and optical domains and is a special voltage-controlled oscillator with an optical output port. It can be used to make a phase-locked loop (PLL) and perform all functions that a PLL is capable of for photonic systems. It can be synchronized to a reference source by means of optical injection locking, electrical injection locking, and PLL. It can also be self-phase locked and self-injection locked to generate a high-stability photonic RF reference. Its applications include high-frequency reference regeneration and distribution, high-gain frequency multiplication, comb-frequecy and square-wave generation, carrier recovery, and clock recovery. We anticipate that such photonic voltage-controlled oscillators (VCOs) will be as important to photonic RF systems as electrical VCOs are to electrical RF systems.
Oscillating Filaments. I. Oscillation and Geometrical Fragmentation
NASA Astrophysics Data System (ADS)
Gritschneder, Matthias; Heigl, Stefan; Burkert, Andreas
2017-01-01
We study the stability of filaments in equilibrium between gravity and internal as well as external pressure using the grid-based AMR code RAMSES. A homogeneous, straight cylinder below a critical line mass is marginally stable. However, if the cylinder is bent, such as with a slight sinusoidal perturbation, an otherwise stable configuration starts to oscillate, is triggered into fragmentation, and collapses. This previously unstudied behavior allows a filament to fragment at any given scale, as long as it has slight bends. We call this process “geometrical fragmentation.” In our realization, the spacing between the cores matches the wavelength of the sinusoidal perturbation, whereas up to now, filaments were thought to be only fragmenting on the characteristic scale set by the mass-to-line ratio. Using first principles, we derive the oscillation period as well as the collapse timescale analytically. To enable a direct comparison with observations, we study the line-of-sight velocity for different inclinations. We show that the overall oscillation pattern can hide the infall signature of cores.
Current oscillations in nanopores
NASA Astrophysics Data System (ADS)
Hyland, Brittany
We develop a simple phenomenological model to describe current oscillations in single, conically shaped nanopores. The model utilizes aspects of reaction rate theory, electrochemical oscillators, and nonlinear dynamical systems. Time series of experimental data were analyzed and compared to time series simulated using the model equations. There is good qualitative agreement between experiment and simulation, though the model needs to be improved in order to obtain better quantitative agreement.
Ultrastable Multigigahertz Photonic Oscillator
NASA Technical Reports Server (NTRS)
Logan, Ronald T., Jr.
1996-01-01
Novel photonic oscillator developed to serve as ultrastable source of microwave and millimeter-wave signals. In system, oscillations generated photonically, then converted to electronic form. Includes self-mode-locked semiconductor laser producing stream of pulses, detected and fed back to laser as input. System also includes fiber-optic-delay-line discriminator, which detects fluctuations of self-mode-locking frequency and generates error signal used in negative-feedback loop to stabilize pulse-repetition frequency.
Rocket Engine Oscillation Diagnostics
NASA Technical Reports Server (NTRS)
Nesman, Tom; Turner, James E. (Technical Monitor)
2002-01-01
Rocket engine oscillating data can reveal many physical phenomena ranging from unsteady flow and acoustics to rotordynamics and structural dynamics. Because of this, engine diagnostics based on oscillation data should employ both signal analysis and physical modeling. This paper describes an approach to rocket engine oscillation diagnostics, types of problems encountered, and example problems solved. Determination of design guidelines and environments (or loads) from oscillating phenomena is required during initial stages of rocket engine design, while the additional tasks of health monitoring, incipient failure detection, and anomaly diagnostics occur during engine development and operation. Oscillations in rocket engines are typically related to flow driven acoustics, flow excited structures, or rotational forces. Additional sources of oscillatory energy are combustion and cavitation. Included in the example problems is a sampling of signal analysis tools employed in diagnostics. The rocket engine hardware includes combustion devices, valves, turbopumps, and ducts. Simple models of an oscillating fluid system or structure can be constructed to estimate pertinent dynamic parameters governing the unsteady behavior of engine systems or components. In the example problems it is shown that simple physical modeling when combined with signal analysis can be successfully employed to diagnose complex rocket engine oscillatory phenomena.
Oscillating asymmetric dark matter
Tulin, Sean; Yu, Hai-Bo; Zurek, Kathryn M. E-mail: haiboyu@umich.edu
2012-05-01
We study the dynamics of dark matter (DM) particle-antiparticle oscillations within the context of asymmetric DM. Oscillations arise due to small DM number-violating Majorana-type mass terms, and can lead to recoupling of annihilation after freeze-out and washout of the DM density. Asymmetric DM oscillations 'interpolate' between symmetric and asymmetric DM freeze-out scenarios, and allow for a larger DM model-building parameter space. We derive the density matrix equations for DM oscillations and freeze-out from first principles using nonequilibrium field theory, and our results are qualitatively different than in previous studies. DM dynamics exhibits particle-vs-antiparticle 'flavor' effects, depending on the interaction type, analogous to neutrino oscillations in a medium. 'Flavor-sensitive' DM interactions include scattering or annihilation through a new vector boson, while 'flavor-blind' interactions include scattering or s-channel annihilation through a new scalar boson. In particular, we find that flavor-sensitive annihilation does not recouple when coherent oscillations begin, and that flavor-blind scattering does not lead to decoherence.
Oscillating asymmetric dark matter
NASA Astrophysics Data System (ADS)
Tulin, Sean; Yu, Hai-Bo; Zurek, Kathryn M.
2012-05-01
We study the dynamics of dark matter (DM) particle-antiparticle oscillations within the context of asymmetric DM. Oscillations arise due to small DM number-violating Majorana-type mass terms, and can lead to recoupling of annihilation after freeze-out and washout of the DM density. Asymmetric DM oscillations "interpolate" between symmetric and asymmetric DM freeze-out scenarios, and allow for a larger DM model-building parameter space. We derive the density matrix equations for DM oscillations and freeze-out from first principles using nonequilibrium field theory, and our results are qualitatively different than in previous studies. DM dynamics exhibits particle-vs-antiparticle "flavor" effects, depending on the interaction type, analogous to neutrino oscillations in a medium. "Flavor-sensitive" DM interactions include scattering or annihilation through a new vector boson, while "flavor-blind" interactions include scattering or s-channel annihilation through a new scalar boson. In particular, we find that flavor-sensitive annihilation does not recouple when coherent oscillations begin, and that flavor-blind scattering does not lead to decoherence.
Kayser, Boris
2012-06-01
To complement the neutrino-physics lectures given at the 2011 International School on Astro Particle Physics devoted to Neutrino Physics and Astrophysics (ISAPP 2011; Varenna, Italy), at the 2011 European School of High Energy Physics (ESHEP 2011; Cheila Gradistei, Romania), and, in modified form, at other summer schools, we present here a written description of the physics of neutrino oscillation. This description is centered on a new way of deriving the oscillation probability. We also provide a brief guide to references relevant to topics other than neutrino oscillation that were covered in the lectures. Neutrinos and photons are by far the most abundant elementary particles in the universe. Thus, if we would like to comprehend the universe, we must understand the neutrinos. Of course, studying the neutrinos is challenging, since the only known forces through which these electrically-neutral leptons interact are the weak force and gravity. Consequently, interactions of neutrinos in a detector are very rare events, so that very large detectors and intense neutrino sources are needed to make experiments feasible. Nevertheless, we have confirmed that the weak interactions of neutrinos are correctly described by the Standard Model (SM) of elementary particle physics. Moreover, in the last 14 years, we have discovered that neutrinos have nonzero masses, and that leptons mix. These discoveries have been based on the observation that neutrinos can change from one 'flavor' to another - the phenomenon known as neutrino oscillation. We shall explain the physics of neutrino oscillation, deriving the probability of oscillation in a new way. We shall also provide a very brief guide to references that can be used to study some major neutrino-physics topics other than neutrino oscillation.
AB INITIO AND CALPHAD THERMODYNAMICS OF MATERIALS
Turchi, P A
2004-04-14
Ab initio electronic structure methods can supplement CALPHAD in two major ways for subsequent applications to stability in complex alloys. The first one is rather immediate and concerns the direct input of ab initio energetics in CALPHAD databases. The other way, more involved, is the assessment of ab initio thermodynamics {acute a} la CALPHAD. It will be shown how these results can be used within CALPHAD to predict the equilibrium properties of multi-component alloys.
Parke, Stephen J.; /Fermilab
2011-07-01
Starting in the late 1960s, neutrino detectors began to see signs that neutrinos, now known to come in the flavors electron ({nu}{sub e}), muon ({nu}{sub {mu}}), and tau ({nu}{sub {tau}}), could transform from one flavor to another. The findings implied that neutrinos must have mass, since massless particles travel at the speed of light and their clocks, so to speak, don't tick, thus they cannot change. What has since been discovered is that neutrinos oscillate at two distinct scales, 500 km/GeV and 15,000 km/GeV, which are defined by the baseline (L) of the experiment (the distance the neutrino travels) divided by the neutrino energy (E). Neutrinos of one flavor can oscillate into neutrinos of another flavor at both L/E scales, but the amplitude of these oscillations is different for the two scales and depends on the initial and final flavor of the neutrinos. The neutrino states that propogate unchanged in time, the mass eigenstates {nu}1, {nu}2, {nu}3, are quantum mechanical mixtures of the electron, muon, and tau neutrino flavors, and the fraction of each flavor in a given mass eigenstate is controlled by three mixing angles and a complex phase. Two of these mixing angles are known with reasonable precision. An upper bound exists for the third angle, called {theta}{sub 13}, which controls the size of the muon neutrino to electron neutrino oscillation at an L/E of 500 km/GeV. The phase is completely unknown. The existence of this phase has important implications for the asymmetry between matter and antimatter we observe in the universe today. Experiments around the world have steadily assembled this picture of neutrino oscillation, but evidence of muon neutrino to electron neutrino oscillation at 500 km/GeV has remained elusive. Now, a paper from the T2K (Tokai to Kamioka) experiment in Japan, reports the first possible observation of muon neutrinos oscillating into electron neutrinos at 500 km/GeV. They see 6 candidate signal events, above an expected background
Oscillate boiling from microheaters
NASA Astrophysics Data System (ADS)
Li, Fenfang; Gonzalez-Avila, S. Roberto; Nguyen, Dang Minh; Ohl, Claus-Dieter
2017-01-01
We report about an intriguing boiling regime occurring for small heaters embedded on the boundary in subcooled water. The microheater is realized by focusing a continuous wave laser beam to about 10 μ m in diameter onto a 165-nm-thick layer of gold, which is submerged in water. After an initial vaporous explosion a single bubble oscillates continuously and repeatedly at several 100 kHz albeit with constant laser power input. The microbubble's oscillations are accompanied with bubble pinch-off, leading to a stream of gaseous bubbles in the subcooled water. The self-driven bubble oscillation is explained with a thermally kicked oscillator caused by surface attachment and by the nonspherical collapses. Additionally, Marangoni stresses induce a recirculating streaming flow which transports cold liquid towards the microheater, reducing diffusion of heat along the substrate and therefore stabilizing the phenomenon to many million cycles. We speculate that this oscillate boiling regime may overcome the heat transfer thresholds observed during the nucleate boiling crisis and offers a new pathway for heat transfer under microgravity conditions.
Oscillations following periodic reinforcement.
Monteiro, Tiago; Machado, Armando
2009-06-01
Three experiments examined behavior in extinction following periodic reinforcement. During the first phase of Experiment 1, four groups of pigeons were exposed to fixed interval (FI 16s or FI 48s) or variable interval (VI 16s or VI 48s) reinforcement schedules. Next, during the second phase, each session started with reinforcement trials and ended with an extinction segment. Experiment 2 was similar except that the extinction segment was considerably longer. Experiment 3 replaced the FI schedules with a peak procedure, with FI trials interspersed with non-food peak interval (PI) trials that were four times longer. One group of pigeons was exposed to FI 20s PI 80s trials, and another to FI 40s PI 160s trials. Results showed that, during the extinction segment, most pigeons trained with FI schedules, but not with VI schedules, displayed pause-peck oscillations with a period close to, but slightly greater than the FI parameter. These oscillations did not start immediately after the onset of extinction. Comparing the oscillations from Experiments 1 and 2 suggested that the alternation of reconditioning and re-extinction increases the reliability and earlier onset of the oscillations. In Experiment 3 the pigeons exhibited well-defined pause-peck cycles since the onset of extinction. These cycles had periods close to twice the value of the FI and lasted for long intervals of time. We discuss some hypotheses concerning the processes underlying behavioral oscillations following periodic reinforcement.
Digital numerically controlled oscillator
NASA Technical Reports Server (NTRS)
Cellier, A.; Huey, D. C.; Ma, L. N. (Inventor)
1980-01-01
The frequency and phase of an output signal from an oscillator circuit are controlled with accuracy by a digital input word. Positive and negative alterations in output frequency are both provided for by translating all values of input words so that they are positive. The oscillator reference frequency is corrected only in one direction, by adding phase to the output frequency of the oscillator. The input control word is translated to a single algebraic sign and the digital 1 is added thereto. The translated input control word is then accumulated. A reference clock signal having a frequency at an integer multiple of the desired frequency of the output signal is generated. The accumulated control word is then compared with a threshold level. The output signal is adjusted in a single direction by dividing the frequency of the reference clock signal by a first integer or by an integer different from the first integer.
NASA Astrophysics Data System (ADS)
Hrkac, Gino; Keatley, Paul S.; Bryan, Matthew T.; Butler, Keith
2015-11-01
The magnetic vortex has sparked the interest of the academic and industrial communities over the last few decades. From their discovery in the 1970s for bubble memory devices to their modern application as radio frequency oscillators, magnetic vortices have been adopted to modern telecommunication and sensor applications. Basic properties of vortex structures in the static and dynamic regime, from a theoretical and experimental point of view, are presented as well as their application in spin torque driven nano-pillar and magnetic tunnel junction devices. Single vortex excitations and phase locking phenomena of coupled oscillators are discussed with an outlook of vortex oscillators in magnetic hybrid structures with imprinted domain confinement and dynamic encryption devices.
Chalcogenide optical parametric oscillator.
Ahmad, Raja; Rochette, Martin
2012-04-23
We demonstrate the first optical parametric oscillator (OPO) based on chalcogenide glass. The parametric gain medium is an As(2)Se(3) chalcogenide microwire coated with a layer of polymer. The doubly-resonant OPO oscillates simultaneously at a Stokes and an anti Stokes wavelength shift of >50 nm from the pump wavelength that lies at λ(P) = 1,552 nm. The oscillator has a peak power threshold of 21.6 dBm and a conversion efficiency of >19%. This OPO experiment provides an additional application of the chalcogenide microwire technology; and considering the transparency of As(2)Se(3) glass extending far in the mid-infrared (mid-IR) wavelengths, the device holds promise for realizing mid-IR OPOs utilizing existing optical sources in the telecommunications wavelength region.
Ab initio dynamical vertex approximation
NASA Astrophysics Data System (ADS)
Galler, Anna; Thunström, Patrik; Gunacker, Patrik; Tomczak, Jan M.; Held, Karsten
2017-03-01
Diagrammatic extensions of dynamical mean-field theory (DMFT) such as the dynamical vertex approximation (DΓ A) allow us to include nonlocal correlations beyond DMFT on all length scales and proved their worth for model calculations. Here, we develop and implement an Ab initio DΓ A approach (AbinitioDΓ A ) for electronic structure calculations of materials. The starting point is the two-particle irreducible vertex in the two particle-hole channels which is approximated by the bare nonlocal Coulomb interaction and all local vertex corrections. From this, we calculate the full nonlocal vertex and the nonlocal self-energy through the Bethe-Salpeter equation. The AbinitioDΓ A approach naturally generates all local DMFT correlations and all nonlocal G W contributions, but also further nonlocal correlations beyond: mixed terms of the former two and nonlocal spin fluctuations. We apply this new methodology to the prototypical correlated metal SrVO3.
Three-cluster dynamics within an ab initio framework
Quaglioni, Sofia; Romero-Redondo, Carolina; Navratil, Petr
2013-09-26
In this study, we introduce a fully antisymmetrized treatment of three-cluster dynamics within the ab initio framework of the no-core shell model/resonating-group method. Energy-independent nonlocal interactions among the three nuclear fragments are obtained from realistic nucleon-nucleon interactions and consistent ab initio many-body wave functions of the clusters. The three-cluster Schrödinger equation is solved with bound-state boundary conditions by means of the hyperspherical-harmonic method on a Lagrange mesh. We discuss the formalism in detail and give algebraic expressions for systems of two single nucleons plus a nucleus. Using a soft similarity-renormalization-group evolved chiral nucleon-nucleon potential, we apply the method to amore » 4He+n+n description of 6He and compare the results to experiment and to a six-body diagonalization of the Hamiltonian performed within the harmonic-oscillator expansions of the no-core shell model. Differences between the two calculations provide a measure of core (4He) polarization effects.« less
Micromechanical Oscillating Mass Balance
NASA Technical Reports Server (NTRS)
Altemir, David A. (Inventor)
1997-01-01
A micromechanical oscillating mass balance and method adapted for measuring minute quantities of material deposited at a selected location, such as during a vapor deposition process. The invention comprises a vibratory composite beam which includes a dielectric layer sandwiched between two conductive layers. The beam is positioned in a magnetic field. An alternating current passes through one conductive layers, the beam oscillates, inducing an output current in the second conductive layer, which is analyzed to determine the resonant frequency of the beam. As material is deposited on the beam, the mass of the beam increases and the resonant frequency of the beam shifts, and the mass added is determined.
New sensitive marginal oscillator
NASA Astrophysics Data System (ADS)
Rahf, L.
1981-09-01
A new type of a sensitive marginal oscillator has been developed for the determination of high magnetic inductions by means of nuclear magnetic resonance. Obtaining a high sensitivity with this measuring principle demands a soft behavior of the oscillator which is a particular feature of the circuit presented. It is shown that this behavior is due to the fact that a very weak positive feedback is established by the inner capacitances of the single field effect transistor used in the circuit. Optimal values for the operation parameters are calculated.
Ultrasound Biomicroscopy Comparison of Ab Interno and Ab Externo Intraocular Lens Scleral Fixation.
Horiguchi, Lie; Garcia, Patricia Novita; Malavazzi, Gustavo Ricci; Allemann, Norma; Gomes, Rachel L R
2016-01-01
Purpose. To compare ab interno and ab externo scleral fixation of posterior chamber intraocular lenses (PCIOL) using ultrasound biomicroscopy (UBM). Methods. Randomized patients underwent ab externo or ab interno scleral fixation of a PCIOL. Ultrasound biomicroscopy was performed 3 to 6 months postoperatively, to determine PCIOL centration, IOL distance to the iris at 12, 3, 6, and 9 hours, and haptics placement in relation to the ciliary sulcus. Results. Fifteen patients were enrolled in the study. The ab externo technique was used in 7 eyes (46.6%) and the ab interno in 8 eyes (53.3%). In the ab externo technique, 14 haptics were located: 4 (28.57%) in the ciliary sulcus; 2 (14.28%) anterior to the sulcus; and 8 (57.14%) posterior to the sulcus, 6 in the ciliary body and 2 posterior to the ciliary body. In the ab interno group, 4 haptics (25.0%) were in the ciliary sulcus, 2 (12.50%) anterior to the sulcus, and 10 (75.0%) posterior to the sulcus, 4 in the ciliary body and 6 posterior to the ciliary body. Conclusions. Ab externo and ab interno scleral fixation techniques presented similar results in haptic placement. Ab externo technique presented higher vertical tilt when compared to the ab interno.
Coupled opto-electronic oscillator
NASA Technical Reports Server (NTRS)
Yao, X. Steve (Inventor); Maleki, Lute (Inventor)
1999-01-01
A coupled opto-electronic oscillator that directly couples a laser oscillation with an electronic oscillation to simultaneously achieve a stable RF oscillation at a high frequency and ultra-short optical pulsation by mode locking with a high repetition rate and stability. Single-mode selection can be achieved even with a very long opto-electronic loop. A multimode laser can be used to pump the electronic oscillation, resulting in a high operation efficiency. The optical and the RF oscillations are correlated to each other.
Erythema ab igne: Usual site, unusual cause.
Manoharan, D
2015-04-01
Erythema ab igne is reticular erythematous pigmented dermatoses seen in patients exposed to prolonged or repeated sub-threshold Infrared radiation inadequate to cause burns. Here, we report a case of erythema ab igne in a 40-year-old male patient seen over the abdomen due to prolonged laptop use.
Glaser, Rainer; Jost, Mary
2012-08-16
The results are reported of an ab initio study of the thermochemistry and of the kinetics of the HOBrO disproportionation reaction 2HOBrO (2) ⇄ HOBr (1) + HBrO(3) (3), reaction ( R4' ), in gas phase (MP2(full)/6-311G*) and aqueous solution (SMD(MP2(full)/6-311G*)). The reaction energy of bromous acid disproportionation is discussed in the context of the coupled reaction system R2-R4 of the FKN mechanism of the Belousov-Zhabotinsky reaction and considering the acidities of HBr and HOBrO(2). The structures were determined of ten dimeric aggregates 4 of bromous acid, (HOBrO)(2), of eight mixed aggregates 5 formed between the products of disproportionation, (HOBr)(HOBrO(2)), and of four transition states structures 6 for disproportionation by direct O-transfer. It was found that the condensation of two HOBrO molecules provides facile access to bromous acid anhydride 7, O(BrO)(2). A discussion of the potential energy surface of Br(2)O(3) shows that O(BrO)(2) is prone to isomerization to the mixed anhydride 8, BrO-BrO(2), and to dissociation to 9, BrO, and 10, BrO(2), and their radical pair 11. Hence, three possible paths from O(BrO)(2) to the products of disproportionation, HOBr and HOBrO(2), are discussed: (1) hydrolysis of O(BrO)(2) along a path that differs from its formation, (2) isomerization of O(BrO)(2) to BrO-BrO(2) followed by hydrolysis, and (3) O(BrO)(2) dissociation to BrO and BrO(2) and their reactions with water. The results of the potential energy surface analysis show that the rate-limiting step in the disproportionation of HOBrO consists of the formation of the hydrate 12a of bromous acid anhydride 7 via transition state structure 14a. The computed activation free enthalpy ΔG(act)(SMD) = 13.6 kcal/mol for the process 2·2a → [14a](‡) → 12a corresponds to the reaction rate constant k(4) = 667.5 M(-1) s(-1) and is in very good agreement with experimental measurements. The potential energy surface analysis further shows that anhydride 7 is
Oscillating Reactions: Two Analogies
ERIC Educational Resources Information Center
Petruševski, Vladimir M.; Stojanovska, Marina I.; Šoptrajanov, Bojan T.
2007-01-01
Oscillating chemical reactions are truly spectacular phenomena, and demonstrations are always appreciated by the class. However, explaining such reactions to high school or first-year university students is problematic, because it may seem that no acceptable explanation is possible unless the students have profound knowledge of both physical…
Wein bridge oscillator circuit
NASA Technical Reports Server (NTRS)
Lipoma, P. C.
1971-01-01
Circuit with minimum number of components provides stable outputs of 2 to 8 volts at frequencies of .001 to 100 kHz. Oscillator exhibits low power consumption, portability, simplicity, and drive capability, it has application as loudspeaker tester and audible alarm, as well as in laboratory and test generators.
NASA Technical Reports Server (NTRS)
Jones, R. T.
1976-01-01
For acoustic tests the violin is driven laterally at the bridge by a small speaker of the type commonly found in pocket transistor radios. An audio oscillator excites the tone which is picked up by a sound level meter. Gross patterns of vibration modes are obtained by the Chladni method.
NASA Technical Reports Server (NTRS)
1995-01-01
Integrated Component Systems, Inc. incorporated information from a NASA Tech Briefs article into a voltage-controlled oscillator it designed for a customer. The company then applied the technology to its series of phase-locked loop synthesizers, which offer superior phase noise performance.
LSND neutrino oscillation results
Louis, W.C.; LSND Collaboration
1997-06-01
The LSND experiment at Los Alamos has conducted searches for {anti {nu}}{sub {mu}} {r_arrow} {anti {nu}}{sub e} oscillations using {anti {nu}}{sub {mu}} from U{sup +} decay at rest and for {nu}{sub {mu}} {r_arrow} {nu}{sub e} oscillations using {nu}{sub {mu}} from {pi}{sup +} decay in flight. For the {anti {nu}}{sub {mu}} {r_arrow} {anti {nu}}{sub e} search, a total excess of 51.8{sub {minus}16.9}{sup +18.7} {+-} 8.0 events is observed with e{sup +} energy between 20 and 60 MeV, while for the {nu}{sub {mu}} {r_arrow} {nu}{sub e} search, a total excess of 18.1 {+-} 6.6 {+-} 4.0 events is observed with e{sup {minus}} energy between 60 and 200 MeV. If attributed to neutrino oscillations, these excesses correspond to oscillation probabilities (averaged over the experimental energies and spatial acceptances) of (0.31 {+-} 0.12 {+-} 0.05)% and (0.26 {+-} 0.10 {+-} 0.05)%, respectively.
Relativistic harmonic oscillator revisited
Bars, Itzhak
2009-02-15
The familiar Fock space commonly used to describe the relativistic harmonic oscillator, for example, as part of string theory, is insufficient to describe all the states of the relativistic oscillator. We find that there are three different vacua leading to three disconnected Fock sectors, all constructed with the same creation-annihilation operators. These have different spacetime geometric properties as well as different algebraic symmetry properties or different quantum numbers. Two of these Fock spaces include negative norm ghosts (as in string theory), while the third one is completely free of ghosts. We discuss a gauge symmetry in a worldline theory approach that supplies appropriate constraints to remove all the ghosts from all Fock sectors of the single oscillator. The resulting ghost-free quantum spectrum in d+1 dimensions is then classified in unitary representations of the Lorentz group SO(d,1). Moreover, all states of the single oscillator put together make up a single infinite dimensional unitary representation of a hidden global symmetry SU(d,1), whose Casimir eigenvalues are computed. Possible applications of these new results in string theory and other areas of physics and mathematics are briefly mentioned.
Monolithic Millimeter Wave Oscillator
NASA Astrophysics Data System (ADS)
Wang, Nan-Lei
There is an increasing interest in the millimeter -wave spectrum for use in communications and for military and scientific applications. The concept of monolithic integration aims to produce very-high-frequency circuits in a more reliable, reproducible way than conventional electronics, and also at lower cost, with smaller size and lighter weight. In this thesis, a negative resistance device is integrated monolithically with a resonator to produce an effective oscillator. This work fills the void resulting from the exclusion of the local oscillator from the monolithic millimeter-wave integrated circuit (MMMIC) receiver design. For convenience a microwave frequency model was used to design the resonator circuit. A 5 GHz hybrid oscillator was first fabricated to test the design; the necessary GaAs process technology was developed for the fabrication. Negative resistance devices and oscillator theory were studied, and a simple but practical model of the Gunn diode was devised to solve the impedance matching problem. Monolithic oscillators at the Ka band (35 GHz) were built and refined. All devices operated in CW mode. By means of an electric-field probe, the output power was coupled into a metallic waveguide for measurement purposes. The best result was 3.63 mW of power output, the highest efficiency was 0.43% and the frequency stability was better than 10-4. In the future, an IMPATT diode could replace the Gunn device to give much higher power and efficiency. A varactor-tuned circuit also suitable for large-scale integration is under study.
Orthogonal polynomials and deformed oscillators
NASA Astrophysics Data System (ADS)
Borzov, V. V.; Damaskinsky, E. V.
2015-10-01
In the example of the Fibonacci oscillator, we discuss the construction of oscillator-like systems associated with orthogonal polynomials. We also consider the question of the dimensions of the corresponding Lie algebras.
Master oscillator stability requirements considerations
Schwarz, H.; Vancraeynest, J.
1986-06-24
This note attempts to point out some ideas about the required stability of the 476 MHz master oscillator, assuming that the phase noise of the oscillator is the only source of noise in the accelerator system.
Ionization oscillations in Hall accelerators
NASA Astrophysics Data System (ADS)
Barral, S.; Peradzyński, Z.
2010-01-01
The underlying mechanism of low-frequency oscillations in Hall accelerators is investigated theoretically. It is shown that relaxation oscillations arise from a competition between avalanche ionization and the advective transport of the working gas. The model derived recovers the slow progression and fast recession of the ionization front. Analytical approximations of the shape of current pulses and of the oscillation frequency are provided for the case of large amplitude oscillations.
NASA Astrophysics Data System (ADS)
Haque, Masud
2014-03-01
We consider Bloch oscillations of interacting quantum particles in a one-dimensional lattice subject to a linear potential gradient (a tilt). For hard-core bosons and for free fermions, we show perfectly periodic behavior of density and momentum distributions. The oscillations can be predominantly position oscillations, or predominantly width oscillations, depending on the initial state. We show how the periodic behavior is modified for weak and strong interactions.
Neutrino Oscillations with Reactor Neutrinos
NASA Astrophysics Data System (ADS)
Cabrera, Anatael
2007-06-01
Prospect measurements of neutrino oscillations with reactor neutrinos are reviewed in this document. The following items are described: neutrinos oscillations status, reactor neutrino experimental strategy, impact of uncertainties on the neutrino oscillation sensitivity and, finally, the experiments in the field. This is the synthesis of the talk delivered during the NOW2006 conference at Otranto (Italy) during September 2006.
NASA Astrophysics Data System (ADS)
Aubert, B.; Bazan, A.; Boucham, A.; Boutigny, D.; De Bonis, I.; Favier, J.; Gaillard, J.-M.; Jeremie, A.; Karyotakis, Y.; Le Flour, T.; Lees, J. P.; Lieunard, S.; Petitpas, P.; Robbe, P.; Tisserand, V.; Zachariadou, K.; Palano, A.; Chen, G. P.; Chen, J. C.; Qi, N. D.; Rong, G.; Wang, P.; Zhu, Y. S.; Eigen, G.; Reinertsen, P. L.; Stugu, B.; Abbott, B.; Abrams, G. S.; Amerman, L.; Borgland, A. W.; Breon, A. B.; Brown, D. N.; Button-Shafer, J.; Clark, A. R.; Dardin, S.; Day, C.; Dow, S. F.; Fan, Q.; Gaponenko, I.; Gill, M. S.; Goozen, F. R.; Gowdy, S. J.; Gritsan, A.; Groysman, Y.; Hernikl, C.; Jacobsen, R. G.; Jared, R. C.; Kadel, R. W.; Kadyk, J.; Karcher, A.; Kerth, L. T.; Kipnis, I.; Kluth, S.; Kral, J. F.; Lafever, R.; LeClerc, C.; Levi, M. E.; Lewis, S. A.; Lionberger, C.; Liu, T.; Long, M.; Luo, L.; Lynch, G.; Luft, P.; Mandelli, E.; Marino, M.; Marks, K.; Matuk, C.; Meyer, A. B.; Minor, R.; Mokhtarani, A.; Momayezi, M.; Nyman, M.; Oddone, P. J.; Ohnemus, J.; Oshatz, D.; Patton, S.; Pedrali-Noy, M.; Perazzo, A.; Peters, C.; Pope, W.; Pripstein, M.; Quarrie, D. R.; Rasson, J. E.; Roe, N. A.; Romosan, A.; Ronan, M. T.; Shelkov, V. G.; Stone, R.; Strother, P. D.; Telnov, A. V.; von der Lippe, H.; Weber, T. F.; Wenzel, W. A.; Zizka, G.; Bright-Thomas, P. G.; Hawkes, C. M.; Kirk, A.; Knowles, D. J.; O'Neale, S. W.; Watson, A. T.; Watson, N. K.; Deppermann, T.; Koch, H.; Krug, J.; Kunze, M.; Lewandowski, B.; Peters, K.; Schmuecker, H.; Steinke, M.; Andress, J. C.; Barlow, N. R.; Bhimji, W.; Chevalier, N.; Clark, P. J.; Cottingham, W. N.; De Groot, N.; Dyce, N.; Foster, B.; Mass, A.; McFall, J. D.; Wallom, D.; Wilson, F. F.; Abe, K.; Hearty, C.; McKenna, J. A.; Thiessen, D.; Camanzi, B.; Harrison, T. J.; McKemey, A. K.; Tinslay, J.; Antohin, E. I.; Blinov, V. E.; Bukin, A. D.; Bukin, D. A.; Buzykaev, A. R.; Dubrovin, M. S.; Golubev, V. B.; Ivanchenko, V. N.; Kolachev, G. M.; Korol, A. A.; Kravchenko, E. A.; Mikhailov, S. F.; Onuchin, A. P.; Salnikov, A. A.; Serednyakov, S. I.; Skovpen, Yu. I.; Telnov, V. I.; Yushkov, A. N.; Booth, J.; Lankford, A. J.; Mandelkern, M.; Pier, S.; Stoker, D. P.; Zioulas, G.; Ahsan, A.; Arisaka, K.; Buchanan, C.; Chun, S.; Faccini, R.; MacFarlane, D. B.; Prell, S. A.; Rahatlou, Sh.; Raven, G.; Sharma, V.; Burke, S.; Callahan, D.; Campagnari, C.; Dahmes, B.; Hale, D.; Hart, P. A.; Kuznetsova, N.; Kyre, S.; Levy, S. L.; Long, O.; Lu, A.; May, J.; Richman, J. D.; Verkerke, W.; Witherell, M.; Yellin, S.; Beringer, J.; DeWitt, J.; Dorfan, D. E.; Eisner, A. M.; Frey, A.; Grillo, A. A.; Grothe, M.; Heusch, C. A.; Johnson, R. P.; Kroeger, W.; Lockman, W. S.; Pulliam, T.; Rowe, W.; Sadrozinski, H.; Schalk, T.; Schmitz, R. E.; Schumm, B. A.; Seiden, A.; Spencer, E. N.; Turri, M.; Walkowiak, W.; Wilder, M.; Williams, D. C.; Chen, E.; Dubois-Felsmann, G. P.; Dvoretskii, A.; Hanson, J. E.; Hitlin, D. G.; Kolomensky, Yu. G.; Metzler, S.; Oyang, J.; Porter, F. C.; Ryd, A.; Samuel, A.; Weaver, M.; Yang, S.; Zhu, R. Y.; Devmal, S.; Geld, T. L.; Jayatilleke, S.; Jayatilleke, S. M.; Mancinelli, G.; Meadows, B. T.; Sokoloff, M. D.; Bloom, P.; Broomer, B.; Erdos, E.; Fahey, S.; Ford, W. T.; Gaede, F.; van Hoek, W. C.; Johnson, D. R.; Michael, A. K.; Nauenberg, U.; Olivas, A.; Park, H.; Rankin, P.; Roy, J.; Sen, S.; Smith, J. G.; Wagner, D. L.; Blouw, J.; Harton, J. L.; Krishnamurthy, M.; Soffer, A.; Toki, W. H.; Warner, D. W.; Wilson, R. J.; Zhang, J.; Brandt, T.; Brose, J.; Dahlinger, G.; Dickopp, M.; Dubitzky, R. S.; Eckstein, P.; Futterschneider, H.; Kocian, M. L.; Krause, R.; Müller-Pfefferkorn, R.; Schubert, K. R.; Schwierz, R.; Spaan, B.; Wilden, L.; Behr, L.; Bernard, D.; Bonneaud, G. R.; Brochard, F.; Cohen-Tanugi, J.; Ferrag, S.; Fouque, G.; Gastaldi, F.; Matricon, P.; Mora de Freitas, P.; Renard, C.; Roussot, E.; T'Jampens, S.; Thiebaux, C.; Vasileiadis, G.; Verderi, M.; Anjomshoaa, A.; Bernet, R.; Di Lodovico, F.; Muheim, F.; Playfer, S.; Swain, J. E.; Falbo, M.; Bozzi, C.; Dittongo, S.; Folegani, M.; Piemontese, L.; Ramusino, A. C.; Treadwell, E.; Anulli, F.; Baldini-Ferroli, R.; Calcaterra, A.; de Sangro, R.; Falciai, D.; Finocchiaro, G.; Patteri, P.; Peruzzi, I. M.; Piccolo, M.; Xie, Y.; Zallo, A.; Bagnasco, S.; Buzzo, A.; Contri, R.; Crosetti, G.; Fabbricatore, P.; Farinon, S.; Lo Vetere, M.; Macri, M.; Minutoli, S.; Monge, M. R.; Musenich, R.; Pallavicini, M.; Parodi, R.; Passaggio, S.; Pastore, F. C.; Patrignani, C.; Pia, M. G.; Priano, C.; Robutti, E.; Santroni, A.; Bartoldus, R.; Dignan, T.; Hamilton, R.; Mallik, U.; Cochran, J.; Crawley, H. B.; Fischer, P. A.; Lamsa, J.; McKay, R.; Meyer, W. T.; Rosenberg, E. I.; Albert, J. N.; Beigbeder, C.; Benkebil, M.; Breton, D.; Cizeron, R.; Du, S.; Grosdidier, G.; Hast, C.; Höcker, A.; Lacker, H. M.; LePeltier, V.; Lutz, A. M.; Plaszczynski, S.; Schune, M. H.; Trincaz-Duvoid, S.; Truong, K.; Valassi, A.; Wormser, G.; Alford, O.; Behne, D.; Bionta, R. M.; Bowman, J.; Brigljević, V.; Brooks, A.; Dacosta, V. A.; Fackler, O.; Fujino, D.; Harper, M.; Lange, D. J.; Mugge, M.; O'Connor, T. G.; Olson, H.; Ott, L.; Parker, E.; Pedrotti, B.; Roeben, M.; Shi, X.; van Bibber, K.; Wenaus, T. J.; Wright, D. M.; Wuest, C. R.; Yamamoto, B.; Carroll, M.; Cooke, P.; Fry, J. R.; Gabathuler, E.; Gamet, R.; George, M.; Kay, M.; McMahon, S.; Muir, A.; Payne, D. J.; Sloane, R. J.; Sutcliffe, P.; Touramanis, C.; Aspinwall, M. L.; Bowerman, D. A.; Dauncey, P. D.; Eschrich, I.; Gunawardane, N. J. W.; Martin, R.; Nash, J. A.; Price, D. R.; Sanders, P.; Smith, D.; Azzopardi, D. E.; Back, J. J.; Dixon, P.; Harrison, P. F.; Newman-Coburn, D.; Potter, R. J. L.; Shorthouse, H. W.; Williams, M. I.; Vidal, P. B.; Cowan, G.; George, S.; Green, M. G.; Kurup, A.; Marker, C. E.; McGrath, P.; McMahon, T. R.; Salvatore, F.; Scott, I.; Vaitsas, G.; Brown, D.; Davis, C. L.; Li, Y.; Pavlovich, J.; Allison, J.; Barlow, R. J.; Boyd, J. T.; Fullwood, J.; Jackson, F.; Khan, A.; Lafferty, G. D.; Savvas, N.; Simopoulos, E. T.; Thompson, R. J.; Weatherall, J. H.; Bard, R.; Dallapiccola, C.; Farbin, A.; Jawahery, A.; Lillard, V.; Olsen, J.; Roberts, D. A.; Schieck, J. R.; Blaylock, G.; Flood, K. T.; Hertzbach, S. S.; Kofler, R.; Lin, C. S.; Willocq, S.; Wittlin, J.; Brau, B.; Cowan, R.; Taylor, F.; Yamamoto, R. K.; Britton, D. I.; Fernholz, R.; Houde, M.; Milek, M.; Patel, P. M.; Trischuk, J.; Lanni, F.; Palombo, F.; Bauer, J. M.; Booke, M.; Cremaldi, L.; Kroeger, R.; Reep, M.; Reidy, J.; Sanders, D. A.; Summers, D. J.; Arguin, J. F.; Beaulieu, M.; Martin, J. P.; Nief, J. Y.; Seitz, R.; Taras, P.; Woch, A.; Zacek, V.; Nicholson, H.; Sutton, C. S.; Cartaro, C.; Cavallo, N.; De Nardo, G.; Fabozzi, F.; Gatto, C.; Lista, L.; Piccolo, D.; Sciacca, C.; Cason, N. M.; LoSecco, J. M.; Alsmiller, J. R. G.; Gabriel, T. A.; Handler, T.; Heck, J.; Iwasaki, M.; Sinev, N. B.; Caracciolo, R.; Colecchia, F.; Dal Corso, F.; Galeazzi, F.; Marzolla, M.; Michelon, G.; Morandin, M.; Posocco, M.; Rotondo, M.; Santi, S.; Simonetto, F.; Stroili, R.; Torassa, E.; Voci, C.; Bailly, P.; Benayoun, M.; Briand, H.; Chauveau, J.; David, P.; De la Vaissière, C.; Del Buono, L.; Genat, J.-F.; Hamon, O.; Leruste, Ph.; Le Diberder, F.; Lebbolo, H.; Lory, J.; Martin, L.; Martinez-Vidal, F.; Roos, L.; Stark, J.; Versillé, S.; Zhang, B.; Manfredi, P. F.; Ratti, L.; Re, V.; Speziali, V.; Frank, E. D.; Gladney, L.; Guo, Q. H.; Panetta, J. H.; Angelini, C.; Batignani, G.; Bettarini, S.; Bondioli, M.; Bosi, F.; Carpinelli, M.; Forti, F.; Gaddi, A.; Gagliardi, D.; Giorgi, M. A.; Lusiani, A.; Mammini, P.; Morganti, M.; Morsani, F.; Neri, N.; Profeti, A.; Paoloni, E.; Raffaelli, F.; Rama, M.; Rizzo, G.; Sandrelli, F.; Simi, G.; Triggiani, G.; Haire, M.; Judd, D.; Paick, K.; Turnbull, L.; Wagoner, D. E.; Albert, J.; Bula, C.; Kelsey, M. H.; Lu, C.; McDonald, K. T.; Miftakov, V.; Sands, B.; Schaffner, S. F.; Smith, A. J. S.; Tumanov, A.; Varnes, E. W.; Bronzini, F.; Buccheri, A.; Bulfon, C.; Cavoto, G.; del Re, D.; Ferrarotto, F.; Ferroni, F.; Fratini, K.; Lamanna, E.; Leonardi, E.; Mazzoni, M. A.; Morganti, S.; Piredda, G.; Safai Tehrani, F.; Serra, M.; Voena, C.; Waldi, R.; Jacques, P. F.; Kalelkar, M.; Plano, R. J.; Adye, T.; Claxton, B.; Dowdell, J.; Egede, U.; Franek, B.; Galagedera, S.; Geddes, N. I.; Gopal, G. P.; Kay, J.; Lidbury, J.; Madani, S.; Metcalfe, S.; Metcalfe, S.; Markey, G.; Olley, P.; Watt, M.; Xella, S. M.; Aleksan, R.; Besson, P.; Bourgeois, P.; Convert, P.; De Domenico, G.; de Lesquen, A.; Emery, S.; Gaidot, A.; Ganzhur, S. F.; Georgette, Z.; Gosset, L.; Graffin, P.; Hamel de Monchenault, G.; Hervé, S.; Karolak, M.; Kozanecki, W.; Langer, M.; London, G. W.; Marques, V.; Mayer, B.; Micout, P.; Mols, J. P.; Mouly, J. P.; Penichot, Y.; Rolquin, J.; Serfass, B.; Toussaint, J. C.; Usseglio, M.; Vasseur, G.; Yeche, C.; Zito, M.; Copty, N.; Purohit, M. V.; Yumiceva, F. X.; Adam, I.; Adesanya, A.; Anthony, P. L.; Aston, D.; Bartelt, J.; Becla, J.; Bell, R.; Bloom, E.; Boeheim, C. T.; Boyarski, A. M.; Boyce, R. F.; Briggs, D.; Bulos, F.; Burgess, W.; Byers, B.; Calderini, G.; Chestnut, R.; Claus, R.; Convery, M. R.; Coombes, R.; Cottrell, L.; Coupal, D. P.; Coward, D. H.; Craddock, W. W.; DeBarger, S.; DeStaebler, H.; Dorfan, J.; Doser, M.; Dunwoodie, W.; Dusatko, J. E.; Ecklund, S.; Fieguth, T. H.; Freytag, D. R.; Glanzman, T.; Godfrey, G. L.; Haller, G.; Hanushevsky, A.; Harris, J.; Hasan, A.; Hee, C.; Himel, T.; Huffer, M. E.; Hung, T.; Innes, W. R.; Jessop, C. P.; Kawahara, H.; Keller, L.; King, M. E.; Klaisner, L.; Krebs, H. J.; Langenegger, U.; Langeveld, W.; Leith, D. W. G. S.; Louie, S. K.; Luitz, S.; Luth, V.; Lynch, H. L.; McDonald, J.; Manzin, G.; Marsiske, H.; Mattison, T.; McCulloch, M.; McDougald, M.; McShurley, D.; Menke, S.; Messner, R.; Metcalfe, S.; Morii, M.; Mount, R.; Muller, D. R.; Nelson, D.; Nordby, M.; O'Grady, C. P.; Olavson, L.; Olsen, J.; O'Neill, F. G.; Oxoby, G.; Paolucci, P.; Pavel, T.; Perl, J.; Pertsova, M.; Petrak, S.; Putallaz, G.; Raines, P. E.; Ratcliff, B. N.; Reif, R.; Robertson, S. H.; Rochester, L. S.; Roodman, A.; Russel, J. J.; Sapozhnikov, L.; Saxton, O. H.; Schietinger, T.; Schindler, R. H.; Schwiening, J.; Sciolla, G.; Seeman, J. T.; Serbo, V. V.; Shapiro, S.; Skarpass, K., Sr.; Snyder, A.; Soderstrom, E.; Soha, A.; Spanier, S. M.; Stahl, A.; Stiles, P.; Su, D.; Sullivan, M. K.; Talby, M.; Tanaka, H. A.; Va'vra, J.; Wagner, S. R.; Wang, R.; Weber, T.; Weinstein, A. J. R.; White, J. L.; Wienands, U.; Wisniewski, W. J.; Young, C. C.; Yu, N.; Burchat, P. R.; Cheng, C. H.; Kirkby, D.; Meyer, T. I.; Roat, C.; Henderson, R.; Khan, N.; Berridge, S.; Bugg, W.; Cohn, H.; Hart, E.; Weidemann, A. W.; Benninger, T.; Izen, J. M.; Kitayama, I.; Lou, X. C.; Turcotte, M.; Bianchi, F.; Bona, M.; Daudo, F.; Di Girolamo, B.; Gamba, D.; Grosso, P.; Smol, A.; Trapani, P. P.; Zanin, D.; Bosisio, L.; Della Ricca, G.; Lanceri, L.; Pompili, A.; Poropat, P.; Prest, M.; Rashevskaia, I.; Vallazza, E.; Vuagnin, G.; Panvini, R. S.; Brown, C.; De Silva, A.; Kowalewski, R.; Pitman, D.; Roney, J. M.; Band, H. R.; Charles, E.; Dasu, S.; Elmer, P.; Johnson, J. R.; Nielsen, J.; Orejudos, W.; Pan, Y.; Prepost, R.; Scott, I. J.; Walsh, J.; Wu, S. L.; Yu, Z.; Zobernig, H.; Moore, T. B.; Neal, H.
2002-02-01
B AB AR, the detector for the SLAC PEP-II asymmetric e +e - B Factory operating at the ϒ(4 S) resonance, was designed to allow comprehensive studies of CP-violation in B-meson decays. Charged particle tracks are measured in a multi-layer silicon vertex tracker surrounded by a cylindrical wire drift chamber. Electromagnetic showers from electrons and photons are detected in an array of CsI crystals located just inside the solenoidal coil of a superconducting magnet. Muons and neutral hadrons are identified by arrays of resistive plate chambers inserted into gaps in the steel flux return of the magnet. Charged hadrons are identified by d E/d x measurements in the tracking detectors and by a ring-imaging Cherenkov detector surrounding the drift chamber. The trigger, data acquisition and data-monitoring systems, VME- and network-based, are controlled by custom-designed online software. Details of the layout and performance of the detector components and their associated electronics and software are presented.
Ab initio phonon limited transport
NASA Astrophysics Data System (ADS)
Verstraete, Matthieu
We revisit the thermoelectric (TE) transport properties of two champion materials, PbTe and SnSe, using fully first principles methods. In both cases the performance of the material is due to subtle combinations of structural effects, scattering, and phase space reduction. In PbTe anharmonic effects are completely opposite to the predicted quasiharmonic evolution of phonon frequencies and to frequently (and incorrectly) cited extrapolations of experiments. This stabilizes the material at high T, but also tends to enhance its thermal conductivity, in a non linear manner, above 600 Kelvin. This explains why PbTe is in practice limited to room temperature applications. SnSe has recently been shown to be the most efficient TE material in bulk form. This is mainly due to a strongly enhanced carrier concentration and electrical conductivity, after going through a phase transition from 600 to 800 K. We calculate the transport coefficients as well as the defect concentrations ab initio, showing excellent agreement with experiment, and elucidating the origin of the double phase transition as well as the new charge carriers. AH Romero, EKU Gross, MJ Verstraete, and O Hellman PRB 91, 214310 (2015) O. Hellman, IA Abrikosov, and SI Simak, PRB 84 180301 (2011)
Erythema ab igne: evolving technology, evolving presentation.
Kesty, Katarina; Feldman, Steven R
2014-11-15
We present a case of a 49-year-old woman with erythema ab igne on her posterior thighs owing to 2-4 hours per day of seat heater use in her car. Erythema ab igne is caused by prolonged exposure to a heat source. It used to be caused mainly by wood stoves used to heat homes. Erythema ab igne is now more often related to other heat sources, including heating pads, laptop computers, and car seat heaters, as in our case. As technology changes, so does the presentation of skin conditions that are related to technology.
Voltage-controlled photonic oscillator.
Savchenkov, A A; Ilchenko, V S; Liang, W; Eliyahu, D; Matsko, A B; Seidel, D; Maleki, L
2010-05-15
We report the development and demonstration of an X-band voltage-controlled photonic oscillator based on a whispering gallery mode resonator made of an electro-optic crystalline material. The oscillator has good spectral purity and wide, agile, linear tunability. We have modified the existing theoretical model of the opto-electronic oscillator to describe the performance of our tunable oscillator and have found a good agreement between the theoretical predictions and the measurement results. We show that the device is promising for higher-frequency applications where high-performance tunable oscillators with wide tunability do not exist.
Stable local oscillator module.
Brocato, Robert Wesley
2007-11-01
This report gives a description of the development of a Stable Local Oscillator (StaLO) multi-chip module (MCM). It is a follow-on report to SAND2006-6414, Stable Local Oscillator Microcircuit. The StaLO accepts a 100MHz input signal and produces output signals at 1.2, 3.3, and 3.6 GHz. The circuit is built as a multi-chip module (MCM), since it makes use of integrated circuit technologies in silicon and lithium niobate as well as discrete passive components. This report describes the development of an MCM-based version of the complete StaLO, fabricated on an alumina thick film hybrid substrate.
Oscillations of complex networks
NASA Astrophysics Data System (ADS)
Wang, Xingang; Lai, Ying-Cheng; Lai, Choy Heng
2006-12-01
A complex network processing information or physical flows is usually characterized by a number of macroscopic quantities such as the diameter and the betweenness centrality. An issue of significant theoretical and practical interest is how such quantities respond to sudden changes caused by attacks or disturbances in recoverable networks, i.e., functions of the affected nodes are only temporarily disabled or partially limited. By introducing a model to address this issue, we find that, for a finite-capacity network, perturbations can cause the network to oscillate persistently in the sense that the characterizing quantities vary periodically or randomly with time. We provide a theoretical estimate of the critical capacity-parameter value for the onset of the network oscillation. The finding is expected to have broad implications as it suggests that complex networks may be structurally highly dynamic.
THz Local Oscillator Technology
NASA Technical Reports Server (NTRS)
Mehdi, Imran
2004-01-01
The last decade has seen a number of technological advancements that have now made it possible to implement fully solid state local oscillator chains up to 2 THz. These chains are composed of cascaded planar multiplier stages that are pumped with W-band high power sources. The high power W-band sources are achieved by power combining MMIC amplifiers and can provide in access of 150 mW with about 10% bandwidth. Planar diode technology has also enabled novel circuit topologies that can take advantage of the high input power and demonstrate significant efficiencies well into the THz range. Cascaded chains to 1.9 THz have now been demonstrated with enough output power to successfully pump hot-electron bolometer mixers in this frequency range. An overview of the current State-of-the-Art of the local oscillator technology will be presented along with highlighting future trends and challenges.
Nonlinear Neural Network Oscillator.
A nonlinear oscillator (10) includes a neural network (12) having at least one output (12a) for outputting a one dimensional vector. The neural ... neural network and the input of the input layer for modifying a magnitude and/or a polarity of the one dimensional output vector prior to the sample of...first or a second direction. Connection weights of the neural network are trained on a deterministic sequence of data from a chaotic source or may be a
Millennial climate oscillation spied
Kerr, R.A.
1996-01-12
Although evaluating the effects of greenhouse gases on climatic warming has been a major growth industry, greenhouse gases are not the only effect on the global climate. Analysing climate records stored in sediments and glacial ice, researchers have detected a slow climate oscillation that has alternately warmed and cooled the world very couple of thousand years for the past hundred thousand years, perhaps millions of years. This article gives an overview of the evidence.
Decay of oscillating universes
NASA Astrophysics Data System (ADS)
Mithani, Audrey Todhunter
2016-08-01
It has been suggested by Ellis et al that the universe could be eternal in the past, without beginning. In their model, the "emergent universe'' exists forever in the past, in an "eternal'' phase before inflation begins. We will show that in general, such an "eternal'' phase is not possible, because of an instability due to quantum tunneling. One candidate model, the "simple harmonic universe'' has been shown by Graham et al to be perturbatively stable; we find that it is unstable with respect to quantum tunneling. We also investigate the stability of a distinct oscillating model in loop quantum cosmology with respect to small perturbations and to quantum collapse. We find that the model has perturbatively stable and unstable solutions, with both types of solutions occupying significant regions of the parameter space. All solutions are unstable with respect to collapse by quantum tunneling to zero size. In addition, we investigate the effect of vacuum corrections, due to the trace anomaly and the Casimir effect, on the stability of an oscillating universe with respect to decay by tunneling to the singularity. We find that these corrections do not generally stabilize an oscillating universe. Finally, we determine the decay rate of the oscillating universe. Although the wave function of the universe lacks explicit time dependence in canonical quantum cosmology, time evolution may be present implicitly through the semiclassical superspace variables, which themselves depend on time in classical dynamics. Here, we apply this approach to the simple harmonic universe, by extending the model to include a massless, minimally coupled scalar field φ which has little effect on the dynamics but can play the role of a "clock''.
Covariant deformed oscillator algebras
NASA Technical Reports Server (NTRS)
Quesne, Christiane
1995-01-01
The general form and associativity conditions of deformed oscillator algebras are reviewed. It is shown how the latter can be fulfilled in terms of a solution of the Yang-Baxter equation when this solution has three distinct eigenvalues and satisfies a Birman-Wenzl-Murakami condition. As an example, an SU(sub q)(n) x SU(sub q)(m)-covariant q-bosonic algebra is discussed in some detail.
Oscillating stagnation point flow
NASA Technical Reports Server (NTRS)
Grosch, C. E.; Salwen, H.
1982-01-01
A solution of the Navier-Stokes equations is given for an incompressible stagnation point flow whose magnitude oscillates in time about a constant, non-zero, value (an unsteady Hiemenz flow). Analytic approximations to the solution in the low and high frequency limits are given and compared with the results of numerical integrations. The application of these results to one aspect of the boundary layer receptivity problem is also discussed.
Oscillating stagnation point flow
NASA Astrophysics Data System (ADS)
Grosch, C. E.; Salwen, H.
1982-11-01
A solution of the Navier-Stokes equations is given for an incompressible stagnation point flow whose magnitude oscillates in time about a constant, non-zero, value (an unsteady Hiemenz flow). Analytic approximations to the solution in the low and high frequency limits are given and compared with the results of numerical integrations. The application of these results to one aspect of the boundary layer receptivity problem is also discussed.
Biochemical Oscillations and Cellular Rhythms
NASA Astrophysics Data System (ADS)
Goldbeter, Albert; Berridge, Foreword by M. J.
1997-04-01
1. Introduction; Part I. Glycolytic Oscillations: 2. Oscillatory enzymes: simple periodic behaviour in an allosteric model for glycolytic oscillations; Part II. From Simple to Complex Oscillatory Behaviour; 3. Birhythmicity: coexistence between two stable rhythms; 4. From simple periodic behaviour to complex oscillations, including bursting and chaos; Part III. Oscillations Of Cyclic Amo In Dictyostelium Cells: 5. Models for the periodic synthesis and relay of camp signals in Dictyostelium discoideum amoebae; 6. Complex oscillations and chaos in the camp signalling system of Dictyostelium; 7. The onset of camp oscillations in Dictyostelium as a model for the ontogenesis of biological rhythms; Part IV. Pulsatile Signalling In Intercellular Communication: 8. Function of the rhythm of intercellular communication in Dictyostelium. Link with pulsatile hormone secretion; Part V. Calcium Oscillations: 9. Oscillations and waves of intracellular calcium; Part VI. The Mitotic Oscillator: 10. Modelling the mitotic oscillator driving the cell division cycle; Part VII. Circadian Rhythms: 11. Towards a model for circadian oscillations in the Drosophila period protein (PER); 12. Conclusions and perspectives; References.
LSND neutrino oscillation results
Louis, W.C.; LSND Collaboration
1996-10-01
The LSND (Liquid Scintillator Neutrino Detector) experiment at Los Alamos has conducted a search for muon antineutrino {r_arrow} electron antineutrino oscillations using muon neutrinos from antimuon decay at rest. The electron antineutrinos are detected via the reaction electron antineutrino + proton {r_arrow} positron + neutron, correlated with the 2.2-MeV gamma from neutron + proton {r_arrow} deuteron + gamma. The use of tight cuts to identify positron events with correlated gamma rays yields 22 events with positron energy between 36 and 60 MeV and only 4.6 {+-} 0.6 background events. The probability that this excess is due entirely to a statistical fluctuation is 4.1 {times} 10{sup -8}. A chi-squared fit to the entire positron sample results in a total excess of 51.8 {sup +18.7}{sub -16.9} {+-} 8.0 events with positron energy between 20 and 60 MeV. If attributed to muon antineutrino {r_arrow} electron antineutrino oscillations, this corresponds to an oscillation probability (averaged over the experimental energy and spatial acceptance) of (0.31 {+-} 0.12 {+-} 0.05){percent}. 10 refs., 7 figs., 1 tab.
LSND neutrino oscillation results
White, D.H.; LSND Collaboration
1997-11-01
The LSND experiment at Los Alamos has conducted a search for {anti v}{sub {mu}} {yields} {anti v}{sub e} oscillations using {anti v}{sub {mu}} from {mu}{sup +} decay at rest. The {anti v}{sub e} are detected via the reaction {anti v}{sub e} p {yields} e{sup +}n, correlated with the 2.2 MeV {gamma} from n p {yields} d {gamma}. The use of tight cuts to identify e{sup +} events with correlated {gamma} rays yielded 22 events with e{sup +} energy between 36 and 60 MeV and only 4.6 {+-} 0.6 background events. The probability that this excess is due entirely to a statistical fluctuation is 4.1 {times} 10{sup {minus}8}. A {chi}{sup 2} fit to the entire e{sup +} sample results in a total excess of 51.8{sub {minus}16.9}{sup +18.7} {+-} 8.0 events with e{sup +} energy between 20 and 60 MeV. If attributed to {anti v}{sub {mu}} {yields} {anti v}{sub e} oscillations, this corresponds to an oscillation probability (averaged over the experimental energy and spatial acceptance) of 0.31 {+-} 0.12 {+-} 0.05%.
Temperature sensitive oscillator
NASA Technical Reports Server (NTRS)
Kleinberg, L. L. (Inventor)
1986-01-01
An oscillator circuit for sensing and indicating temperature by changing oscillator frequency with temperature comprises a programmable operational amplifier which is operated on the roll-off portion of its gain versus frequency curve and has its output directly connected to the inverting input to place the amplifier in a follower configuration. Its output is also connected to the non-inverting input by a capacitor with a crystal or other tuned circuit also being connected to the non-inverting input. A resistor is connected to the program input of the amplifier to produce a given set current at a given temperature, the set current varying with temperature. As the set current changes, the gain-bandwidth of the amplifier changes and, in turn, the reflected capacitance across the crystal changes, thereby providing the desired change in oscillator frequency by pulling the crystal. There is no requirement that a crystal employed with this circuit display either a linear frequency change with temperature or a substantial frequency change with temperature.
Nonlinear Oscillators in Space Physics
NASA Technical Reports Server (NTRS)
Lester,Daniel; Thronson, Harley
2011-01-01
We discuss dynamical systems that produce an oscillation without an external time dependent source. Numerical results are presented for nonlinear oscillators in the Em1h's atmosphere, foremost the quasi-biennial oscillation (QBOl. These fluid dynamical oscillators, like the solar dynamo, have in common that one of the variables in a governing equation is strongly nonlinear and that the nonlinearity, to first order, has particular form. of 3rd or odd power. It is shown that this form of nonlinearity can produce the fundamental li'equency of the internal oscillation. which has a period that is favored by the dynamical condition of the fluid. The fundamental frequency maintains the oscillation, with no energy input to the system at that particular frequency. Nonlinearities of 2nd or even power could not maintain the oscillation.