Nonlocality of the Aharonov-Bohm effect
NASA Astrophysics Data System (ADS)
Aharonov, Yakir; Cohen, Eliahu; Rohrlich, Daniel
2016-04-01
Although the Aharonov-Bohm and related effects are familiar in solid-state and high-energy physics, the nonlocality of these effects has been questioned. Here we show that the Aharonov-Bohm effect has two very different aspects. One aspect is instantaneous and nonlocal; the other aspect, which depends on entanglement, unfolds continuously over time. While local, gauge-invariant variables may occasionally suffice for explaining the continuous aspect, we argue that they cannot explain the instantaneous aspect. Thus the Aharonov-Bohm effect is, in general, nonlocal.
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. PMID:25537848
Thermoelectric effect in Aharonov-Bohm structures
NASA Astrophysics Data System (ADS)
Lu, Xin; Wang, Jian-Sheng; Morrel, William G.; Ni, Xiaoxi; Wu, Chang-Qin; Li, Baowen
2015-01-01
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.
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
The electric Aharonov-Bohm effect
NASA Astrophysics Data System (ADS)
Weder, Ricardo
2011-05-01
The seminal paper of Aharonov and Bohm [Phys. Rev. 115, 485 (1959)], 10.1103/PhysRev.115.485 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)], 10.1103/PhysRevLett.99.210401 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), 10.1007/s00220-008-0579-1; J. Math. Phys. 50
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
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. PMID:24476790
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. PMID:22587255
Aharonov-Bohm effect in a class of noncommutative theories
NASA Astrophysics Data System (ADS)
Das, Ashok; Falomir, H.; Nieto, M.; Gamboa, J.; Méndez, F.
2011-08-01
The Aharonov-Bohm effect including spin-noncommutative effects is considered. At linear order in θ, the magnetic field is gauge invariant although spatially strongly anisotropic. Despite this anisotropy, the Schrödinger-Pauli equation is separable through successive unitary transformations and the exact solution is found. The scattering amplitude is calculated and compared with the usual case. In the noncommutative Aharonov-Bohm case the differential cross section is independent of θ.
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. PMID:22401183
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.
NASA Astrophysics Data System (ADS)
Semenov, Andrew G.; Zaikin, Andrei D.
2010-01-01
We investigate the effect of electron-electron interactions on Aharonov-Bohm (AB) current oscillations in nanorings formed by a chain of metallic quantum dots. We demonstrate that electron-electron interactions cause electron dephasing thereby suppressing the amplitude of AB oscillations at all temperatures down to T=0. The crossover between thermal and quantum dephasing is found to be controlled by the ring perimeter. Our predictions can be directly tested in future experiments.
Aharonov-Bohm effect induced by circularly polarized light
NASA Astrophysics Data System (ADS)
Sigurdsson, H.; Kibis, O. V.; Shelykh, I. A.
2015-11-01
We demonstrated theoretically that the strong electron interaction with circularly polarized photons in ring-like nanostructures changes the phase of electron wave. This optically-induced effect is caused by the breaking of time-reversal symmetry and is similar to the Aharonov-Bohm effect. As a consequence of this phenomenon, the conductance of mesoscopic rings irradiated by a circularly polarized electromagnetic wave behaves as an oscillating function of the intensity and frequency of the wave.
Spin- and localization-induced fractional Aharonov-Bohm effect
NASA Astrophysics Data System (ADS)
Emperador, A.; Pederiva, F.; Lipparini, E.
2003-09-01
We performed a theoretical analysis of the Aharonov-Bohm oscillations of the ground-state energy of quasi-one-dimensional quantum rings in a magnetic field, recently observed in conductance experiments, by means of quantum Monte Carlo calculations. The model rings considered contain N=10 and N=4 electrons, with radii of 20 and 120 nm, respectively. These parameters give a close description of the nanorings analyzed in the experiments. In particular, the two cases well reproduce the high- and low-electron-density regimes. For N=10, we have found fractional Aharonov-Bohm effect with a period Φ0/2 due to the changes in the total spin of the ground state. For N=4, we have found fractional oscillations with a period Φ0/4, which are shown to be a consequence of strong localization.
Aharonov-Bohm effect in cyclotron and synchrotron radiations
NASA Astrophysics Data System (ADS)
Bagrov, V. G.; Gitman, D. M.; Levin, A.; Tlyachev, V. B.
2001-07-01
We study the impact of Aharonov-Bohm solenoid on the radiation of a charged particle moving in a constant uniform magnetic field. With this aim in view, exact solutions of Klein-Gordon and Dirac equations are found in the magnetic-solenoid field. Using such solutions, we calculate exactly all the characteristics of one-photon spontaneous radiation both for spinless and spinning particle. Considering non-relativistic and relativistic approximations, we analyze cyclotron and synchrotron radiations in detail. Radiation peculiarities caused by the presence of the solenoid may be considered as a manifestation of Aharonov-Bohm effect in the radiation. In particular, it is shown that new spectral lines appear in the radiation spectrum. Due to angular distribution peculiarities of the radiation intensity, these lines can in principle be isolated from basic cyclotron and synchrotron radiation spectra.
Aharonov-Bohm effect of excitons in nanorings
NASA Astrophysics Data System (ADS)
Hu, Hui; Zhu, Jia-Lin; Li, Dai-Jun; Xiong, Jia-Jiong
2001-05-01
The magnetic field effects on excitons in an InAs nanoring are studied theoretically. By numerically diagonalizing the effective-mass Hamiltonian of the problem that can be separated into terms in center-of-mass and relative coordinates, we calculate the low-lying excitonic energy levels and oscillator strengths as a function of the ring width and the strength of an external magnetic field. It is shown that in the presence of Coulomb correlation, the so-called Aharonov-Bohm effect of excitons exists in a finite (but small) width nanoring. However, when the ring width becomes large, the non-simply-connected geometry of nanorings is destroyed, causing the suppression of the Aharonov-Bohm effect. The analytical results are obtained for a narrow-width nanoring in which the radial motion is the fastest one and adiabatically decoupled from the azimuthal motions. The conditional probability distribution calculated for the low-lying excitonic states allows identification of the presence of the Aharonov-Bohm effect. The linear optical susceptibility is also calculated as a function of the magnetic field, to be compared with the future measurements of optical emission experiments on InAs nanorings.
Dispersionless forces and the Aharonov-Bohm effect
NASA Astrophysics Data System (ADS)
Batelaan, H.; Becker, M.
2015-11-01
The independence of the Aharonov-Bohm phase shift on particle velocity is one of its defining properties. The classical counterpart to this dispersionless behavior is the absence of forces along the direction of motion of the particle. A reevaluation of the experimental demonstration that forces are absent in the AB physical system is given, including previously unpublished data. It is shown that the debate on the presence or absence of forces is not settled. Experiments that measure the influence of magnetic permeability on forces and search for dispersionless quantum forces are proposed.
Analogue Aharonov-Bohm effect in neo-Newtonian theory
NASA Astrophysics Data System (ADS)
Anacleto, M. A.; Salako, I. G.; Brito, F. A.; Passos, E.
2015-12-01
We address the issues of the scattering of massless planar scalar waves by an acoustic black hole in neo-Newtonian hydrodynamics. We then compute the differential cross section through the use of the partial wave approach in the neo-Newtonian theory which is a modification of the usual Newtonian theory that correctly incorporates the effects of pressure. We mainly show that the scattering of planar waves leads to a modified analogue Aharonov-Bohm effect due to a nontrivial response of the parameters defining the equation of state.
Spectroscopic detectability of the molecular Aharonov-Bohm effect
NASA Astrophysics Data System (ADS)
Englman, R.
2016-01-01
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."
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." PMID:26772550
Non-Abelian Aharonov-Bohm effect with the time-dependent gauge fields
NASA Astrophysics Data System (ADS)
Hosseini Mansoori, Seyed Ali; Mirza, Behrouz
2016-04-01
We investigate the non-Abelian Aharonov-Bohm (AB) effect for time-dependent gauge fields. We prove that the non-Abelian AB phase shift related to time-dependent gauge fields, in which the electric and magnetic fields are written in the adjoint representation of SU (N) generators, vanishes up to the first order expansion of the phase factor. Therefore, the flux quantization in a superconductor ring does not appear in the time-dependent Abelian or non-Abelian AB effect.
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).
Revisiting the Marton, Simpson, and Suddeth experimental confirmation of the Aharonov-Bohm effect
NASA Astrophysics Data System (ADS)
Macdougall, James; Singleton, Douglas; Vagenas, Elias C.
2015-09-01
We perform an "archeological" study of one of the original experiments used as evidence for the static, time-independent Aharonov-Bohm effect. Since the experiment in question [1] involved a time varying magnetic field we show that there are problems with the explanation of this experiment as a confirmation of the static Aharonov-Bohm effect - specifically the previous analysis ignored the electric field which arises in conjunction with a time-varying magnetic flux. We further argue that the results of this experiment do in fact conform exactly to the recent prediction [2,3] of a cancellation between the magnetic and electric phase shifts for the time-dependent Aharonov-Bohm effect. To resolve this issue a new time-dependent Aharonov-Bohm experiment is called for.
Thermoelectric effects in a rectangular Aharonov-Bohm geometry
NASA Astrophysics Data System (ADS)
Pye, A. J.; Faux, D. A.; Kearney, M. J.
2016-04-01
The thermoelectric transport properties of a rectangular Aharonov-Bohm ring at low temperature are investigated using a theoretical approach based on Green's functions. The oscillations in the transmission coefficient as the field is varied can be used to tune the thermoelectric response of the ring. Large magnitude thermopowers are obtainable which, in conjunction with low conductance, can result in a high thermoelectric figure of merit. The effects of single site impurities and more general Anderson disorder are considered explicitly in the context of evaluating their effect on the Fano-type resonances in the transmission coefficient. Importantly, it is shown that even for moderate levels of disorder, the thermoelectric figure of merit can remain significant, increasing the appeal of such structures from the perspective of specialist thermoelectric applications.
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
Absence of the Electric Aharonov-Bohm Effect due to Induced Charges
NASA Astrophysics Data System (ADS)
Wang, Rui-Feng
2015-09-01
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.
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
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)
Excitonic Aharonov-Bohm effect: Unstrained versus strained type-I semiconductor nanorings
NASA Astrophysics Data System (ADS)
Tadić, M.; Čukarić, N.; Arsoski, V.; Peeters, F. M.
2011-09-01
We study how mechanical strain affects the magnetic field dependence of the exciton states in type-I semiconductor nanorings. Strain spatially separates the electron and hole in (In,Ga)As/GaAs nanorings which is beneficial for the occurrence of the excitonic Aharonov-Bohm (AB) effect. In narrow strained (In,Ga)As/GaAs nanorings the AB oscillations in the exciton ground-state energy are due to anticrossings with the first excited state. No such AB oscillations are found in unstrained GaAs/(Al,Ga)As nanorings irrespective of the ring width. Our results are obtained within an exact numerical diagonalization scheme and are shown to be accurately described by a two-level model with off-diagonal coupling t. The later transfer integral expresses the Coulomb coupling between states of electron-hole pairs. We also found that the oscillator strength for exciton recombination in (In,Ga)As/GaAs nanorings exhibits AB oscillations, which are superimposed on a linear increase with magnetic field. Our results agree qualitatively with recent experiments on the excitonic Aharonov-Bohm effect in type-I (In,Ga)As/GaAs nanorings.
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 Constraint for Fusion
NASA Astrophysics Data System (ADS)
Yahalom, Asher
It was shown that an Aharonov-Bohm (AB) effect exists in magnetohydrodynamics (MHD). This effect is best described in terms of the MHD variational variables. If a MHD flow has a non trivial topology some of the functions appearing in the MHD Lagrangian are non-single valued. Some of those functions are analogue to the phases in the AB celebrated effect. While the manifestation of the quantum AB effect is in interference fringe patterns, the manifestation of the MHD Aharonov-Bohm effect is through a new dynamical conservation law. This local conservation law will be shown to constrain the dynamics of MHD flows including fusion scenarios. Bibliography
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.
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.
Internal frame dragging and a global analog of the Aharonov-Bohm effect
March-Russell, J. ); Preskill, J. ); Wilczek, F. )
1992-04-27
It is shown that the breakdown of a {ital global} symmetry group to a discrete subgroup can lead to analogs of the Aharonov-Bohm effect. At sufficiently low momentum transfer, the cross section for scattering of a particle with nontrivial Z{sub 2} charge off a global vortex is almost equal to (but definitely different from) maximal Aharonov-Bohm scattering; the effect goes away at large momentum transfer. The scattering of a spin-1/2 particle off a magnetic vortex provides an amusing experimentally realizable example.
Gravitational Aharonov-Bohm effect due to noncommutative BTZ black hole
NASA Astrophysics Data System (ADS)
Anacleto, M. A.; Brito, F. A.; Passos, E.
2015-04-01
In this paper we consider the scattering of massless planar scalar waves by a noncommutative BTZ black hole. We compute the differential cross section via the partial wave approach, and we mainly show that the scattering of planar waves leads to a modified Aharonov-Bohm effect due to spacetime noncommutativity.
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).
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).
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.
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.
Spin accumulation assisted by the Aharonov-Bohm-Fano effect of quantum dot structures.
Gong, Wei-Jiang; Han, Yu; Wei, Guo-Zhu; Du, An
2012-01-01
: 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. PMID:22985404
Reply to "Comment on `Role of potentials in the Aharonov-Bohm effect' "
NASA Astrophysics Data System (ADS)
Vaidman, Lev
2015-08-01
The preceding Comment challenged my claim that potentials might be just auxiliary mathematical tools and that they are not necessary for explaining physical phenomena. The Comment did not confront my explanation without the potentials of the Aharonov-Bohm effects that appeared in the original article, but stated that I cannot apply this explanation for seven other examples. In my reply, using my method, I provide explanations of one of the examples, show that two other examples are not relevant, and agree that the remaining examples require further analysis. However, I argue that none of the examples provides robust counterexamples to my claim, similar to the original Aharonov-Bohm setups which were explained in my article, so the Comment does not refute my claim.
Spin accumulation assisted by the Aharonov-Bohm-Fano effect of quantum dot structures
2012-01-01
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. PMID:22985404
Time-dependent Pauli equation in the presence of the Aharonov-Bohm effect
NASA Astrophysics Data System (ADS)
Bouguerra, Y.; Bounames, A.; Maamache, M.; Saadi, Y.
2008-04-01
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.
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.
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.
The semi-classical limit of the Aharonov-Bohm effect: The actualized approach
NASA Astrophysics Data System (ADS)
Kholmetskii, A. L.; Yarman, T.
2013-03-01
We suggest an approach, which formally allows us to describe the Aharonov-Bohm (AB) effect in the semi-classical language. In the framework of this approach, we keep the classical concepts of electromagnetic field and force. At the same time, instead of point-like classical charges, we introduce a finite-size elementary charge distribution, modelling the wave-like packet, associated with the motion of a given electron. In this case we derive the force on the wave-like packet on behalf of the solenoid via the minimization of action defined through the Lagrangian density (instead of the Lagrangian used in common classical electrodynamics of point-like charges). We show that this force due to the solenoid, being dependent on the vector potential, yields the common expression for the magnetic AB phase, when the original wave packet is splitted into a superposition of two packets encirling the solenoid. We also analyze in the classical language the implementation of total momentum conservation law for the isolated system "moving electrons plus elongated solenoid" and determine the properties of finite-size charge distribution, when this law is fulfilled. The results obtained are discussed.
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
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
2014-01-01
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
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
NASA Astrophysics Data System (ADS)
Grochol, M.; Grosse, F.; Zimmermann, R.
2006-09-01
The optical exciton Aharonov-Bohm effect—i.e., an oscillatory component in the energy of optically active (bright) states—is investigated in nanorings. It is shown that a small effective electron mass, strong confinement of the electron, and high barrier for the hole, achieved, e.g., by an InAs nanoring embedded in an AlGaSb quantum well, are favorable for observing the optical exciton Aharonov-Bohm effect. The second derivative of the exciton energy with respect to the magnetic field is utilized to extract Aharonov-Bohm oscillations even for the lowest bright state unambiguously. A connection between the theories for infinitesimal narrow and finite width rings is established. Furthermore, the magnetization is compared to the persistent current, which oscillates periodically with the magnetic field and confirms thus the nontrivial (connected) topology of the wave function in the nanoring.
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. PMID:21805987
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. PMID:26565819
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.
Lorentz violation correction to the Aharonov-Bohm scattering
NASA Astrophysics Data System (ADS)
Anacleto, M. A.
2015-10-01
In this paper, using a (2 +1 )-dimensional field theory approach, we study the Aharonov-Bohm (AB) scattering with Lorentz symmetry breaking. We obtain the modified scattering amplitude to the AB effect due to the small Lorentz violation correction in the breaking parameter and prove that up to one loop the model is free from ultraviolet divergences.
How quantum impenetrability affects Aharonov-Bohm scattering?
NASA Astrophysics Data System (ADS)
Afanasev, G. N.; Shilov, V. M.
It is shown that different forms of quantum impenetrability lead to different physical consequences. This should be kept in mind in analyzing experimental data. The relativistic impenetrability conditions are considered and the corresponding relativistic Aharonov-Bohm cross-sections are obtained. The possibility of the AB effect occurrence in simply-connected space regions is discussed.
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
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.
Thermoelectric effect in an Aharonov-Bohm ring with an embedded quantum dot.
Zheng, Jun; Chi, Feng; Lu, Xiao-Dong; Zhang, Kai-Cheng
2012-01-01
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. PMID:22369454
Aharonov-Bohm effect in the tunnelling of a quantum rotor in a linear Paul trap.
Noguchi, Atsushi; Shikano, Yutaka; Toyoda, Kenji; Urabe, Shinji
2014-01-01
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]. PMID:24820051
NASA Astrophysics Data System (ADS)
Maslov, A. V.; Citrin, D. S.
2003-03-01
This work demonstrates that the Aharonov-Bohm effect for excitons, practically indistinguishable from the numerical noise without an applied electric field, becomes clearly evident in the optical absorption once the electric field is applied in the plane containing the nanoring. The enhancement arises as a result of the field-induced delocalization of the relative electron-hole motion around the entire ring. The excitonic effects are essential to describe even qualitatively the absorption spectra.
Realization of adiabatic Aharonov-Bohm scattering with neutrons
NASA Astrophysics Data System (ADS)
Sjöqvist, Erik; Almquist, Martin; Mattsson, Ken; Gürkan, Zeynep Nilhan; Hessmo, Björn
2015-11-01
The adiabatic Aharonov-Bohm (AB) effect is a manifestation of the Berry phase acquired when some slow variables take a planar spin around a loop. While the effect has been observed in molecular spectroscopy, direct measurement of the topological phase shift in a scattering experiment has been elusive in the past. Here, we demonstrate an adiabatic AB effect by explicit simulation of the dynamics of unpolarized very slow neutrons that scatter on a long straight current-carrying wire.
Valley Zeeman energy in monolayer MoS2 quantum rings: Aharonov-Bohm effect
NASA Astrophysics Data System (ADS)
Oliveira, D.; Fu, Jiyong; Villegas-Lelovsky, L.; Dias, A. C.; Qu, Fanyao
2016-05-01
We investigate the valley Zeeman energy (VZE) in monolayer MoS2 quantum rings, subjected to a magnetic flux Φ only passing through a hole region enclosed by the inner circle of the ring. To gain insight on our numerical outcomes for finite two-dimensional rings, an analytic solution in the one-dimensional limit (zero ring width) is also presented. Although no magnetic field is applied inside the ring region, we observe finite VZEs. Interestingly, in contrast to the usual linear scenario, the VZE of the rings exhibits an oscillatory dependence on Φ with possible vanishing valley Zeeman effect even in a nonzero magnetic flux due to Aharonov-Bohm type effect. On the other hand, within one period of oscillations the VZE increases linearly with Φ . Furthermore, for a given magnetic flux, the valley Zeeman effect is more pronounced in a ring with a stronger quantum confinement. Thus the VZE can be tuned by either magnetic flux or ring confinement or both of them. This opens a new route for controlling the valley Zeeman effect using a nonmagnetic means.
NASA Astrophysics Data System (ADS)
Tadić, M.; Arsoski, V.; Čukarić, N.; Peeters, F. M.
2013-12-01
The excitonic Aharonov-Bohm oscillations in type-I nanorings are found to be caused by anticrossings between exciton states. These anticrossings are analyzed by a tight-binding-like model of exciton states. The criteria for the existence of the excitonic Aharonov-Bohm oscillations are formulated. For nanorings of realistic width and height, the range of values of the inner radius where the excitonic Aharonov-Bohm oscillations exist is found.
Aharonov-Bohm phase for an electromagnetic wave background
NASA Astrophysics Data System (ADS)
Bright, Max; Singleton, Douglas; Yoshida, Atsushi
2015-09-01
The canonical Aharonov-Bohm effect is usually studied with time-independent potentials. In this work, we investigate the Aharonov-Bohm phase acquired by a charged particle moving in time-dependent potentials. In particular, we focus on the case of a charged particle moving in the time-varying field of a plane electromagnetic wave. We work out the Aharonov-Bohm phase using both the potential (i.e. oint A_μ dx ^μ ) and the field (i.e. 1/2int F_{μ ν } dσ ^{μ ν }) forms of the Aharonov-Bohm phase. We give conditions in terms of the parameters of the system (frequency of the electromagnetic wave, the size of the space-time loop, amplitude of the electromagnetic wave) under which the time-varying Aharonov-Bohm effect could be observed.
Aharonov-Bohm detection of two-dimensional magnetostatic cloaks
NASA Astrophysics Data System (ADS)
Valagiannopoulos, Constantinos A.; Askarpour, Amir Nader; Alù, Andrea
2015-12-01
Two-dimensional magnetostatic cloaks, even when perfectly designed to mitigate the magnetic field disturbance of a scatterer, may be still detectable with Aharonov-Bohm (AB) measurements, and therefore may affect quantum interactions and experiments with elongated objects. We explore a multilayered cylindrical cloak whose permeability profile is tailored to nullify the magnetic-flux perturbation of the system, neutralizing its effect on AB measurements, and simultaneously optimally suppress the overall scattering. In this way, our improved magnetostatic cloak combines substantial mitigation of the magnetostatic scattering response with zero detectability by AB experiments.
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. PMID:26188995
Fano effect in the Andreev reflection of the Aharonov-Bohm-Fano ring with Majorana bound states
NASA Astrophysics Data System (ADS)
Jiang, Cui; Zheng, Yi-Song
2015-06-01
The Andreev reflection in an Aharonov-Bohm-Fano ring induced by Majorana bound states (MBSs) is theoretically investigated. We find that compared with the Fano effect in the normal electron tunneling process, the Fano effect here is more determined by the structural parameters, i.e., the quantum dot level, the dot-MBS coupling, and the dot-MBS and MBS-lead couplings. By transforming the ring into its Nambu representation, we present a comprehensive analysis about the quantum interference in the Andreev reflection, and then explain the reason for the occurrence of the Fano effect. These results will be helpful for understanding the quantum interference in the MBS-assisted Andreev reflection.
NASA Astrophysics Data System (ADS)
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.
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. PMID:22842114
Polarized excitons in nanorings and the optical Aharonov-Bohm effect
NASA Astrophysics Data System (ADS)
Govorov, A. O.; Ulloa, S. E.; Karrai, K.; Warburton, R. J.
2002-08-01
The quantum nature of matter lies in the wave function phases that accumulate while particles move along their trajectories. A prominent example is the Aharonov-Bohm phase, which has been studied in connection with the conductance of nanostructures. However, optical response in solids is determined by neutral excitations, for which no sensitivity to magnetic flux would be expected. We propose a mechanism for the topological phase of a neutral particle, a polarized exciton confined to a semiconductor quantum ring. We predict that this magnetic-field induced phase may strongly affect excitons in a system with cylindrical symmetry, resulting in switching between ``bright'' exciton ground states and novel ``dark'' states with nearly infinite lifetimes. Since excitons determine the optical response of semiconductors, the predicted phase can be used to tailor photon emission from quantum nanostructures.
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.
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)
Maamache, M.; Lahoulou, C.; Saadi, Y.
2009-05-01
Invariant operator method for discrete or continuous spectrum eigenvalue and unitary transformation approach are employed to study the two-dimensional time-dependent Pauli equation in presence of the Aharonov-Bohm effect (AB) and external scalar potential. For the spin particles the problem with the magnetic field is that it introduces a singularity into wave equation at the origin. A physical motivation is to replace the zero radius flux tube by one of radius R, with the additional condition that the magnetic field be confined to the surface of the tube, and then taking the limit R → 0 at the end of the computations. We point that the invariant operator must contain the step function θ(r - R). Consequently, the problem becomes more complicated. In order to avoid this difficulty, we replace the radius R by ρ(t)R, where ρ(t) is a positive time-dependent function. Then at the end of calculations we take the limit R → 0. The qualitative properties for the invariant operator spectrum are described separately for the different values of the parameter C appearing in the nonlinear auxiliary equation satisfied by ρ(t), i.e., C > 0, C = 0, and C < 0. Following the C's values the spectrum of quantum states is discrete (C > 0) or continuous (C <= 0).
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." PMID:19113511
Magnetic edge states in Aharonov-Bohm graphene quantum rings
NASA Astrophysics Data System (ADS)
Farghadan, R.; Saffarzadeh, A.; Heidari Semiromi, E.
2013-12-01
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.
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.
NASA Astrophysics Data System (ADS)
Grochol, Michal; Zimmermann, Roland
2007-11-01
Transition energies and oscillator strengths of excitons in dependence on magnetic field are investigated in types I and II semiconductor nanorings. A slight deviation from circular (concentric) shape of the type II nanoring gives a better observability of the Aharonov-Bohm oscillations since the ground state is always optically active. Kinetic equations for the exciton occupation are solved with acoustic phonon scattering as the major relaxation process, and absorption and luminescence spectra are calculated, showing deviations from equilibrium. The presence of a nonradiative exciton decay leads to a quenching of the integrated photoluminescence with magnetic field.
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. PMID:27152813
Electronic energy levels of nanorings with impurities and Aharonov-Bohm effects
NASA Astrophysics Data System (ADS)
Ramírez, S.
2011-10-01
By modeling impurities along a nanoring as general potential forms the Schrödinger equation for ballistic electrons is shown to separate in cylindrical coordinates. We find an analytical eigenvalue equation for N delta-function-barrier impurities in the presence of magnetic flux. Previous calculations of the electronic states of a one-dimensional (1D) and two-dimensional (2D) nanoring for only one or two impurities modeled by equal square barriers is explicitly extended to three and four different or equal impurities modeled as delta-barrier, square-barrier, or delta-well potential forms. This is shown to be generalizable to any number N. Effects on the energy spectra due to magnetic flux and different kinds and numbers of impurities are compared in 1D and 2D nanorings.
The Aharonov-Bohm Effect and Transport Properties in Graphene Nanostructures
NASA Astrophysics Data System (ADS)
Lungu, Mihai; Giugiulan, Raluca; Lungu, Antoanetta; Bunoiu, Madalin; Neculae, Adrian
2013-12-01
This paper investigates the possibility to improve the filtering process of flue gas by separation of suspended nanoparticle using dielectrophoresis. The study focuses on the particles having an average radius of about 50-150 nm, that cannot be filtrated by classical techniques but have a harmful effect for environment and human health. The size distribution nanoparticles collected from the flue gas filters of a hazardous waste incinerator plant were evaluated. Based on obtained experimental data and a proposed mathematical model, the concentration distribution of nanoparticle suspended in flue gas inside a microfluidic separation device was analyzed by numerical simulations, using the finite element method. The performances of the device were described in terms of three new specific quantities related to the separation process, namely Recovery, Purity and Separation Efficiency. The simulations could provide the optimal values of control parameters for separation process, and aim to be a useful tool in designing microfluidic devices for separating nanoparticle from combustion gases.
NASA Astrophysics Data System (ADS)
Roshanzamir-Nikou, M.; Goudarzi, H.
2016-02-01
A strong magnetic field significantly affects the intrinsic magnetic moment of fermions. In quantum electrodynamics, it was shown that the anomalous magnetic moment of an electron arises kinematically, while it results from a dynamical interaction with an external magnetic field for hadrons (proton). Taking the anomalous magnetic moment of a fermion into account, we find an exact expression for the boundstate energy and the corresponding eigenfunctions of a two-dimensional nonrelativistic spin-1/2 harmonic oscillator with a centripetal barrier (known as the isotonic oscillator) including an Aharonov-Bohm term in the presence of a strong magnetic field. We use the Laplace transform method in the calculations. We find that the singular solution contributes to the phase of the wave function at the origin and the phase depends on the spin and magnetic flux.
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.
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
Aharonov-Bohm oscillation modes in double-barrier nanorings
NASA Astrophysics Data System (ADS)
Zhu, Jia-Lin; Yu, Xiquan; Dai, Zhensheng; Hu, Xiao
2003-02-01
The energy spectrum and Aharonov-Bohm (AB) effect in a two-dimensional nanoring interrupted by two identical barriers are studied, and a way of labeling a state according to the node numbers of the wave function in the absence of magnetic flux is introduced. It is found that a magnetic flux φ can modify both the phase and amplitude of wave functions due to the presence of the barriers. AB oscillations are strongly affected by the double barriers, and there are two modes of strong AB oscillations, named O and X modes. The energy levels of O and X modes are occasionally degenerate at φ=0 and 0.5, respectively, and the corresponding wave functions of both degenerate states are localized and can be greatly modified by a small change of φ. The O mode of AB oscillations, which does not exist in the parallel double-barrier ring usually used in experiments, presents an interesting picture and suggests other related phenomena.
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. PMID:24785639
Entanglement between static and flying qubits in an Aharonov Bohm double electrometer
NASA Astrophysics Data System (ADS)
Schomerus, Henning; Robinson, John P.
2007-03-01
We consider the phase-coherent transport of electrons passing through an Aharonov Bohm ring while interacting with a tunnel charge in a double quantum dot (representing a charge qubit) which couples symmetrically to both arms of the ring. For Aharonov Bohm flux ΦAB = h/2e we find that electrons can only be transmitted when they flip the charge qubit's pseudospin parity an odd number of times. The perfect correlations of the dynamics of the pseudospin and individual electronic transmission and reflection events can be used to entangle the charge qubit with an individual passing electron.
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.
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.
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 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.
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. PMID:27300989
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.
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. PMID:26648477
NASA Astrophysics Data System (ADS)
Vaidman, Lev; Dennis, Mark; Popescu, Sandu
2010-01-01
This is a call for contributions to a special issue of Journal of Physics A: Mathematical and Theoretical dedicated to the subject of quantum phases and highlighting the impact of the discovery of the Aharonov--Bohm effect and of the Berry phase across physics. Researchers working in the area are invited to submit papers of original research to this issue. Editorial policy The Editorial Board has invited Lev Vaidman, Mark Dennis and Sandu Popescu to serve as Guest Editors for the special issue. The criteria for acceptance of contributions are as follows: Contributions will be refereed and processed according to the usual procedure and high standards of the journal. Papers should be original and should contain substantial new results. All contributions will be refereed and processed according to the usual procedure of the journal. Papers should report original and significant research that has not already been published. Guidelines for preparation of contributions The DEADLINE for contributed papers will be 1 February 2010. This deadline will allow the special issue to appear in September 2010. Advice on publishing your work in Journal of Physics A: Mathematical and Theoretical www.iop.org/Journals/jphysa. Contributions to the special issue should be submitted electronically, if possible, by web upload at www.iop.org/Journals/jphysa, or by email to jphysa@iop.org, quoting 'JPhysA Special Issue— Quantum Phases'. Submissions should ideally be in standard LaTeX form. Please see the website for further information on electronic submissions. Authors unable to submit electronically may send hard-copy contributions to: Publishing Administrators, Journal of Physics A, IOP Publishing, Dirac House, Temple Back, Bristol BS1 6BE, UK. Please quote 'JPhysA Special Issue— Quantum Phases'. All contributions should be accompanied by a read-me file or covering letter giving the postal and e-mail addresses for correspondence. The Publishing Office should be notified of any
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.
Observation of Optical Signature of the Aharonov-Bohm Phase in Type-II Quantum Dots
NASA Astrophysics Data System (ADS)
Kuskovsky, Igor; MacDonald, W.; Tamargo, M. C.; Govorov, A. O.; Wei, X.; Tadic, M.; Peeters, F. M.
2006-03-01
Recent theoretical studies^1,2 on the optical response of type-II excitons in the magnetic field have shown that the excitons will acquire the Aharonov-Bohm (AB) phase as the electrical dipole, formed due to carrier separation, interacts with the field, resulting in the field dependent exciton energy and the emission intensity. Experimentally, the former has been reported^3; however, the behavior of the intensity is still not fully understood. We present results of magneto-photoluminescence studies on type-II ZnTe/ZnSe quantum dots (QDs) formed in Zn-Se-Te multilayer systems^4; this ensures that electron move within the x-y plane. The observed strong oscillations in the intensity is explained in terms of the AB effect^1,2,5 due to the electron motion around a stack of QDs, when the hole is strongly localized in one them. This is in qualitative agreement with the theoretical predictions^2. 1. Kalameitsev, et al., JETP Lett. 68, 669 (1998); Govorov, et al., PRB R66, 081309 (2002); Janssens, et al., PRB 67, 235325 (2003). 2. Janssens, et al., PRB 69, 235320 (2004). 3. Ribeiro, et al., PRL 92, 126402 (2004). 4. Gu, et al.., PRB 71 045340 (2005). 5. Dias da Silva, et al., PRB 70, 155318 (2004).
Exotic Dirac Wavepackets Accumulating Aharonov-Bohm-type Phase in Free Space
NASA Astrophysics Data System (ADS)
Kaminer, Ido; Nemirovsky, Jonathan; Rechtsman, Mikael; Bekenstein, Rivka; Segev, Mordechai
2013-05-01
Following the seminal 1958 paper by Aharonov-Bohm (AB), it is expected that two parts of the wavefunction of an electron can accumulate phase difference even when they are confined to a region in space with zero EM field. The AB effect was groundbreaking: the EM vector potential is a physical quantity affecting the outcome of experiments directly, not only through the fields extracted from it. But is the EM potential a real necessity for an AB-type effect? Can such effect exist in a potential-free system such as free-space? Here, we find self-accelerating solutions of the potential-free Dirac equation, for massive/massless fermions/bosons. These exotic Dirac particles mimic the dynamics of a free-charge moving under a ``virtual'' EM field. They accelerate even though no field is acting on them (and no charge is defined): the entire dynamics is a direct result of the initial conditions. We show that such particles display an effective AB effect that can be explained by a ``virtual'' potential that ``causes'' the exact same acceleration. We prove that one can create all effects induced by EM fields by only controlling the initial conditions of a wave pattern. Altogether, measurements taken along the trajectory cannot distinguish between a real force and this virtual force: self-induced by the wavepacket itself. The measurable effects of this virtual force are real by all measurable quantities. These phenomena can be observed in various settings: e.g., optical waves in hyperbolic metamaterials, and matter waves in honeycomb interference structures.
Aharonov-Bohm phases in a quantum LC circuit
NASA Astrophysics Data System (ADS)
Cao, ChunJun; Yao, Yuan; Zhitnitsky, Ariel R.
2016-03-01
We study novel types of contributions to the partition function of the Maxwell system defined on a small compact manifold. These contributions, often not addressed in the perturbative treatment with physical photons, emerge as a result of tunneling transitions between topologically distinct but physically identical vacuum winding states. These new terms give an extra contribution to the Casimir pressure, yet to be measured. We argue that this effect is highly sensitive to a small external electric field, which should be contrasted with the conventional Casimir effect, where the vacuum photons are essentially unaffected by any external field. Furthermore, photons will be emitted from the vacuum in response to a time-dependent electric field, similar to the dynamical Casimir effect in which real particles are radiated from the vacuum due to the time-dependent boundary conditions. We also propose an experimental setup using a quantum LC circuit to detect this novel effect. We expect physical electric charges to appear on the capacitor plates when the system dimension is such that coherent Aharonov-Bohm phases can be maintained over macroscopically large distances.
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. PMID:23552181
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.
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. PMID:25763968
Gate controlled Aharonov-Bohm-type oscillations from single neutral excitons in quantum rings
NASA Astrophysics Data System (ADS)
Ding, F.; Akopian, N.; Li, B.; Perinetti, U.; Govorov, A.; Peeters, F. M.; Bof Bufon, C. C.; Deneke, C.; Chen, Y. H.; Rastelli, A.; Schmidt, O. G.; Zwiller, V.
2010-08-01
We report on a magnetophotoluminescence study of single self-assembled semiconductor nanorings which are fabricated by molecular-beam epitaxy combined with AsBr3 in situ etching. Oscillations in the neutral exciton radiative recombination energy and in the emission intensity are observed under an applied magnetic field. Further, we control the period of the oscillations with a gate potential that modifies the exciton confinement. We infer from the experimental results, combined with calculations, that the exciton Aharonov-Bohm effect may account for the observed effects.
Force-free gravitational redshift: proposed gravitational Aharonov-Bohm experiment.
Hohensee, Michael A; Estey, Brian; Hamilton, Paul; Zeilinger, Anton; Müller, Holger
2012-06-01
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. PMID:23003927
Mode Dependency of Quantum Decoherence Studied via an Aharonov-Bohm Interferometer
NASA Astrophysics Data System (ADS)
Lo, Tung-Sheng; Lin, Yiping; Wu, Phillip M.; Ling, Dah-Chin; Chi, C. C.; Chen, Jeng-Chung
2016-02-01
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.
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. PMID:26967397
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.
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.
Vacuum polarization of planar charged fermions with Coulomb and Aharonov-Bohm potentials
NASA Astrophysics Data System (ADS)
Khalilov, V. R.; Mamsurov, I. V.
2016-02-01
Vacuum polarization of charged massless fermions is investigated in the superposition of Coulomb and Aharonov-Bohm (AB) potentials in 2 + 1 dimensions. For this purpose, we construct the Green function of the two-dimensional Dirac equation with Coulomb and AB potentials (via the regular and irregular solutions of the radial Dirac equation) and then calculate the vacuum polarization charge density in the so-called subcritical and supercritical regimes. In the supercritical regime, the Green function has a discontinuity in the complex plane of “energy” due to the singularities on the negative energy axis; these singularities are situated on the unphysical sheet and related to the creation of infinitely many quasistationary fermionic states with negative energies. We expect that our results will be helpful in gaining deeper understanding of the fundamental problem of quantum electrodynamics which can be applied to the problems of charged impurity screening in graphene taking into consideration the electron spin.
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
2015-01-01
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. PMID:26158768
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.
Wave-packet rectification in nonlinear electronic systems: a tunable Aharonov-Bohm diode.
Li, Yunyun; Zhou, Jun; Marchesoni, Fabio; Li, Baowen
2014-01-01
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. PMID:24691462
Wave-packet rectification in nonlinear electronic systems: A tunable Aharonov-Bohm diode
Li, Yunyun; Zhou, Jun; Marchesoni, Fabio; Li, Baowen
2014-01-01
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. PMID:24691462
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. PMID:25361112
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. PMID:25525160
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.
Phase shifts and phase π jumps in four-terminal waveguide Aharonov-Bohm interferometers
NASA Astrophysics Data System (ADS)
Kreisbeck, Christoph; Kramer, Tobias; Buchholz, Sven S.; Fischer, Saskia F.; Kunze, Ulrich; Reuter, Dirk; Wieck, Andreas D.
2010-10-01
Quantum coherent properties of electrons can be studied in Aharonov-Bohm (AB) interferometers. We investigate both experimentally and theoretically the transmission phase evolution in a four-terminal quasi-one-dimensional AlGaAs/GaAs-based waveguide AB ring. As main control parameter besides the magnetic field, we tune the Fermi wave number along the pathways using a top-gate. Our experimental results and theoretical calculations demonstrate the strong influence of the measurement configuration upon the AB-resistance-oscillation phase in a four-terminal device. While the nonlocal setup displays continuous phase shifts of the AB oscillations, the phase remains rigid in the local voltage-probe setup. Abrupt phase jumps are found in all measurement configurations. We analyze the phase shifts as functions of the magnetic field and the Fermi energy and provide a detailed theoretical model of the device. Scattering and reflections in the arms of the ring are the source of abrupt phase jumps by π .
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
NASA Astrophysics Data System (ADS)
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.
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
Aharonov-Bohm interference in gate-defined ring of high-mobility graphene
NASA Astrophysics Data System (ADS)
Kim, Minsoo; Lee, Hu-Jong
2015-03-01
Recent progress in preparing a high-quality graphene layer enables one to investigate the intrinsic carrier transport nature in the material. Here, we report the signature of conservation of the Berry's phase with preserved valley symmetry in Aharonov-Bohm (AB) interferometers fabricated on monolayer graphene with high carrier mobility, where the graphene was sandwiched between two thin hexagonal boron nitride (h-BN) layers. In measurements, charge carriers were confined in an AB ring-shaped potential well formed by the dual-gate operation of the bottom and top gates and the four-terminal magneto-conductance (MC) was measured with varying charge carrier density and temperature. Graphene in the device was in the ballistic regime as confirmed by the conductance quantization in steps of ΔG = 4e2/ h in a constricted conducting channel of separate measurements. We observed h/e periodic modulation of MC and the zero-field conductance minimum with a negative MC background. The phase information of AB interference strongly suggests that carriers in the graphene in our devices preserve the intrinsic Dirac transport nature, which would be conveniently utilized for valleytronics in graphene.
Analytical expression of Kondo temperature in quantum dot embedded in Aharonov-Bohm ring.
Yoshii, Ryosuke; Eto, Mikio
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∕|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: PMID:22112300
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. PMID:24096892
On the Aharonov-Bohm Operators with Varying Poles: The Boundary Behavior of Eigenvalues
NASA Astrophysics Data System (ADS)
Noris, Benedetta; Nys, Manon; Terracini, Susanna
2015-11-01
We consider a magnetic Schrödinger operator with magnetic field concentrated at one point (the pole) of a domain and half integer circulation, and we focus on the behavior of Dirichlet eigenvalues as functions of the pole. Although the magnetic field vanishes almost everywhere, it is well known that it affects the operator at the spectral level (the Aharonov-Bohm effect, Phys Rev (2) 115:485-491, 1959). Moreover, the numerical computations performed in (Bonnaillie-Noël et al., Anal PDE 7(6):1365-1395, 2014; Noris and Terracini, Indiana Univ Math J 59(4):1361-1403, 2010) show a rather complex behavior of the eigenvalues as the pole varies in a planar domain. In this paper, in continuation of the analysis started in (Bonnaillie-Noël et al., Anal PDE 7(6):1365-1395, 2014; Noris and Terracini, Indiana Univ Math J 59(4):1361-1403, 2010), we analyze the relation between the variation of the eigenvalue and the nodal structure of the associated eigenfunctions. We deal with planar domains with Dirichlet boundary conditions and we focus on the case when the singular pole approaches the boundary of the domain: then, the operator loses its singular character and the k-th magnetic eigenvalue converges to that of the standard Laplacian. We can predict both the rate of convergence and whether the convergence happens from above or from below, in relation with the number of nodal lines of the k-th eigenfunction of the Laplacian. The proof relies on the variational characterization of eigenvalues, together with a detailed asymptotic analysis of the eigenfunctions, based on an Almgren-type frequency formula for magnetic eigenfunctions and on the blow-up technique.
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.
Scattering of spin-polarized electron in an Aharonov Bohm potential
NASA Astrophysics Data System (ADS)
Khalilov, V. R.; Ho, Choon-Lin
2008-05-01
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.
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. PMID:23615899
Aharonov-Bohm interferometer based on n -p junctions in graphene nanoribbons
NASA Astrophysics Data System (ADS)
Mreńca-Kolasińska, A.; Heun, S.; Szafran, B.
2016-03-01
We demonstrate that the phenomenon of current confinement along graphene n -p junctions at high magnetic fields can be used to form an Aharonov-Bohm interferometer. The interference system exploits a closed n -p junction that can be induced by a floating gate within the sample, and coupling of the junction currents with the edge currents in the quantum Hall regime. Operation of the device requires current splitting at the edge and the n -p junction contacts which is found for armchair ribbons at low Fermi energy.
Control of the transmission phase in an asymmetric four-terminal Aharonov-Bohm interferometer
NASA Astrophysics Data System (ADS)
Buchholz, Sven S.; Fischer, Saskia F.; Kunze, Ulrich; Bell, Matthew; Reuter, Dirk; Wieck, Andreas D.
2010-07-01
Phase sensitivity and thermal dephasing in coherent electron transport in quasi-one-dimensional (1D) waveguide rings of an asymmetric four-terminal geometry are studied by magnetotransport measurements. We demonstrate the electrostatic control of the phase in Aharonov-Bohm resistance oscillations and investigate the impact of the measurement circuitry on decoherence. Phase rigidity is broken due to the ring geometry: orthogonal waveguide cross junctions and 1D leads minimize reflections and resonances between leads allowing for a continuous electron transmission phase shift. The measurement circuitry influences dephasing: thermal averaging dominates in the nonlocal measurement configuration while additional influence of potential fluctuations becomes relevant in the local configuration.
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. PMID:24237543
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.
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.
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. PMID:21970845
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.
Aharonov-Bohm oscillations in Dirac semimetal Cd3As2 nanowires.
Wang, Li-Xian; Li, Cai-Zhen; Yu, Da-Peng; Liao, Zhi-Min
2016-01-01
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. PMID:26902716
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.
Bai, Long; Zhang, Rong; Duan, Chen-Long
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
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. PMID:23004240
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.
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.
Quantum motion of a point particle in the presence of the Aharonov-Bohm potential in curved space
NASA Astrophysics Data System (ADS)
Silva, Edilberto O.; Ulhoa, Sérgio C.; Andrade, Fabiano M.; Filgueiras, Cleverson; Amorim, R. G. G.
2015-11-01
The nonrelativistic quantum dynamics of a spinless charged particle in the presence of the Aharonov-Bohm potential in curved space is considered. We chose the surface as being a cone defined by a line element in polar coordinates. The geometry of this line element establishes that the motion of the particle can occur on the surface of a cone or an anti-cone. As a consequence of the nontrivial topology of the cone and also because of two-dimensional confinement, the geometric potential should be taken into account. At first, we establish the conditions for the particle describing a circular path in such a context. Because of the presence of the geometric potential, which contains a singular term, we use the self-adjoint extension method in order to describe the dynamics in all space including the singularity. Expressions are obtained for the bound state energies and wave functions.
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. PMID:25770531
NASA Astrophysics Data System (ADS)
Smirnov, A. G.
2015-12-01
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.
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. PMID:24745284
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. PMID:24483873
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. PMID:27165662
An experimental proposal to test the physical effect of the vector potential.
Wang, Rui-Feng
2016-01-01
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. PMID:26822526
An experimental proposal to test the physical effect of the vector potential
NASA Astrophysics Data System (ADS)
Wang, Rui-Feng
2016-01-01
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 Astrophysics Data System (ADS)
Karrasch, C.; Meden, V.
2009-01-01
We study a quantum dot Josephson junction inside an Aharonov-Bohm environment. The geometry is modeled by an Anderson impurity coupled to two directly linked BCS leads. We illustrate that the well-established picture of the low-energy physics being governed by an interplay of two distinct (singlet and doublet) phases is still valid for this interferometric setup. The phase boundary depends, however, nonmonotonically on the coupling strength between the superconductors, causing the system to exhibit re-entrance behavior and multiple phase transitions. We compute the zero-temperature Josephson current and demonstrate that it can become negative in the singlet phase by virtue of the Coulomb interaction U . As a starting point, the limit of large superconducting energy gaps Δ=∞ is solved analytically. In order to tackle arbitrary Δ<∞ and U>0 , we employ a truncated functional renormalization-group scheme which was previously demonstrated to give quantitatively reliable results for the quantum dot Josephson problem.
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.
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. PMID:24824563
Aharonov-Bohm Beats in Excitonic Luminescence from Quantum Rings and Type-II Quantum Dots
NASA Astrophysics Data System (ADS)
Dias da Silva, Luis; Shahbazyan, Tigran
2005-03-01
We study the absorption spectrum of neutral magnetoexcitons confined in ring-like structures. Despite their neutral character, excitons exhibit strong modulation effects on the energy and oscillator strength in the presence of magnetic fields [1] that have been recently observed [2]. We calculate the absorption coefficient α for neutral excitons confined in circular ring geometries with radii Re for electrons and Rh for holes. A particularly interesting situation comes about when Re!=Rh and a net radial charge polarization arises. In this case, we consider an attractive Coulomb interaction proportional to (Re- Rh)-1 and the excitonic absorption peak shows oscillatory behavior as function of the applied magnetic field both in position and amplitude. Such oscillations strongly depend on the dipole moment P=e(Rh-Re) of the exciton and on the dielectric constant of the system. Such intensity changes could in principle be experimentally observed with single dot spectroscopy in quantum rings [3]. Supported by the NSF-IMC and NSF-RUI [1] A.O. Govorov et al. Phys. Rev. B 66 081309 (2002); A.O. Govorov et al. Physica E 13, 297 (2002). [2] E. Ribeiro et al. Phys Rev. Lett. 92 126402 (2004). [3] R.J. Warburton et al. Nature 405 (6789) 926 (2000).
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.
ERIC Educational Resources Information Center
Matteucci, G.
2007-01-01
In the so-called electric Aharonov-Bohm effect, a quantum interference pattern shift is produced when electrons move in an electric field free region but, at the same time, in the presence of a time-dependent electric potential. Analogous fringe shifts are observed in interference experiments where electrons, travelling through an electrostatic…
The Aharanov-Bohm effect, magnetic monopoles and reversal in spin-ice lattices.
Pollard, Shawn D; Zhu, Yimei
2013-06-01
The proof of the Aharonov-Bohm (AB) effect has been one of the most important experiments of the last century and used as essential evidence for the theory of gauge fields. In this article, we look at its fundamental relation to the Dirac monopole and string. Despite the Dirac string being invisible to the AB effect, it can be used to study emergent quasiparticles in condensed matter settings that behave similar to the fundamental monopoles and strings between them. We utilize phase-imaging method based on the AB effect to study the ordering in a one-model system - that of frustrated spin ice - to understand the ordering processes that occur during a magnetic field reversal cycle. The reversal is linked to the propagation of monopole defects linked by flux channels, reminiscent of Dirac strings. Monopole interactions govern the defect densities within the lattice. Furthermore, we exploit these interactions to propose a new ordering method in which high degrees of ground-state ordering can be achieved in a frustrated system. PMID:23549453
NASA Astrophysics Data System (ADS)
Milošević, M. M.; Tadić, M.; Peeters, F. M.
2008-11-01
The influence of lateral asymmetry on the electronic structure and optical transitions in elliptical strained InAs nanorings is analyzed in the presence of a perpendicular magnetic field. Two-dimensional rings are assumed to have elliptical inner and outer boundaries oriented in mutually orthogonal directions. The influence of the eccentricity of the ring on the energy levels is analyzed. For large eccentricity of the ring, we do not find any Aharonov-Bohm effect, in contrast to circular rings. Rather, the single-particle states of the electrons and the holes are localized as in two laterally coupled quantum dots formed in the lobes of the nanoring. Our work indicates that the control of shape is important for the existence of the Aharonov-Bohm effect in semiconductor nanorings.
Milošević, M M; Tadić, M; Peeters, F M
2008-11-12
The influence of lateral asymmetry on the electronic structure and optical transitions in elliptical strained InAs nanorings is analyzed in the presence of a perpendicular magnetic field. Two-dimensional rings are assumed to have elliptical inner and outer boundaries oriented in mutually orthogonal directions. The influence of the eccentricity of the ring on the energy levels is analyzed. For large eccentricity of the ring, we do not find any Aharonov-Bohm effect, in contrast to circular rings. Rather, the single-particle states of the electrons and the holes are localized as in two laterally coupled quantum dots formed in the lobes of the nanoring. Our work indicates that the control of shape is important for the existence of the Aharonov-Bohm effect in semiconductor nanorings. PMID:21832775
Topological insulator Bi2Te3 nanowire field effect devices
NASA Astrophysics Data System (ADS)
Jauregui, Luis A.; Zhang, Genqiang; Wu, Yue; Chen, Yong P.
2012-02-01
Bismuth telluride (Bi2Te3) has been studied extensively as one of the best thermoelectric materials and recently shown to be a prototype topological insulator with nontrivial conducting surface states. We have grown Bi2Te3 nanowires by a two-step solution phase reaction and characterized their material and structural properties by XRD, TEM, XPS and EDS. We fabricate both backgated (on SiO2/Si) and top-gated (with ALD high-k gate dielectric such as Al2O3 or HfO2) field effect devices on such nanowires with diameters ˜50nm. Ambipolar field effect and a resistance modulation of up to 600% at low temperatures have been observed. The 4-terminal resistance shows insulating behavior (increasing with decreasing temperature) from 300 K to 50K, then saturates in a plateau for temperatures below 50K, consistent with the presence of metallic surface state. Aharonov--Bohm (AB) oscillations are observed in the magneto-resistance with a magnetic field parallel to the nanowire, providing further evidence of the presence of surface state conduction Finally, a prominent weak anti-localization (WAL) feature that weakens with increasing magnetic field and/or temperature is observed in the magneto-resistance with a magnetic field perpendicular to the nanowire.
Fano-Rashba effect in thermoelectricity of a double quantum dot molecular junction.
Liu, Ys; Hong, Xk; Feng, Jf; Yang, Xf
2011-01-01
We examine the relation between the phase-coherent processes and spin-dependent thermoelectric effects in an Aharonov-Bohm (AB) interferometer with a Rashba quantum dot (QD) in each of its arm by using the Green's function formalism and equation of motion (EOM) technique. Due to the interplay between quantum destructive interference and Rashba spin-orbit interaction (RSOI) in each QD, an asymmetrical transmission node splits into two spin-dependent asymmetrical transmission nodes in the transmission spectrum and, as a consequence, results in the enhancement of the spin-dependent thermoelectric effects near the spin-dependent asymmetrical transmission nodes. We also examine the evolution of spin-dependent thermoelectric effects from a symmetrical parallel geometry to a configuration in series. It is found that the spin-dependent thermoelectric effects can be enhanced by controlling the dot-electrode coupling strength. The simple analytical expressions are also derived to support our numerical results.PACS numbers: 73.63.Kv; 71.70.Ej; 72.20.Pa. PMID:22151740
Quantum transport in topological insulator nanoribbon field effect and Josephson devices
NASA Astrophysics Data System (ADS)
Kayyalha, Morteza; Jauregui, Luis; Kazakov, Aleksander; Pettes, Michael; Miotkowski, Ireneusz; Shi, Li; Rokhinson, Leonid; Chen, Yong
The spin-helical topological surface states (TSS) of topological insulators have attracted great attention in the past few years as an excellent platform to study topological transport and other exotic physics such as Majorana fermions. Here we present experiments studying quantum transport of TSS in topological insulator nanoribbon (TINR) field effect devices with normal as well as superconducting contacts. In Bi2Te3 NRs with normal contacts, we observe that the conductance vs. axial magnetic field exhibits Aharonov-Bohm (AB) oscillations with an alternating phase of zero and π, depending periodically on the Fermi momentum kF tuned by an applied back-gate voltage, consistent with the 1D sub-band structure formed by circumferentially quantized TSS. We also investigated the Josephson effects in BiSbTeSe2 TINRs with superconducting Nb contacts. We measured the gate voltage and temperature dependence of the supercurrent and multiple Andreev reflections (MAR), to probe phase coherent transport via TSS
Transport measurements of the topological surface states in Bi2Te3 nanoribbon field effect devices
NASA Astrophysics Data System (ADS)
Jauregui, Luis A.; Pettes, Michael T.; Shi, Li; Rokhinson, Leonid P.; Chen, Yong P.
2013-03-01
We have grown nanoribbons (NRs) of Bi2Te3, a prototype topological insulator, by CVD and characterized them by TEM, Raman Spectroscopy and EDS. We fabricate backgated field effect devices where the chemical potential can be tuned and ambipolar field effect has been observed. The as-grown NRs are n-type and the 4-terminal resistance (R4p) versus temperature (T) shows a metallic behavior. Applying a sufficiently negative Vg, the R4p vs T displays an insulating behavior that saturates in a plateau at T < 100K, suggesting a metallic surface conduction dominant at low temperatures. Aharonov-Bohm (AB) oscillations of surface conducting carriers are observed in the magneto-resistance (MR) with a magnetic (B) field parallel to the NR axis. We have also measured the Shubnikov de Haas (SdH) oscillations with the B-field perpendicular to the NR axis at different carrier densities (n). The extrapolated Landau level crossing at 1/B = 0 is 0.5 and the extracted cyclotron mass from the T-dependence of the SdH oscillations is proportional to √{ n}, providing direct evidence of the Dirac fermion nature of the topological surface state. Gate-tunable weak anti-localization is observed and the extracted number of decoupled coherent conduction channels is 2 at the charge neutrality point.
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.
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)
Shech, Elay
2015-09-01
This paper looks at the nature of idealizations and representational structures appealed to in the context of the fractional quantum Hall effect, specifically, with respect to the emergence of anyons and fractional statistics. Drawing on an analogy with the Aharonov-Bohm effect, it is suggested that the standard approach to the effects—(what we may call) the topological approach to fractional statistics—relies essentially on problematic idealizations that need to be revised in order for the theory to be explanatory. An alternative geometric approach is outlined and endorsed. Roles for idealizations in science, as well as consequences for the debate revolving around so-called essential idealizations, are discussed.
NASA Astrophysics Data System (ADS)
Horta-Piñeres, Sindi; Elizabeth Escorcia-Salas, G.; Mikhailov, I. D.; Sierra-Ortega, J.
2014-11-01
The energy spectrum of a positively charged exciton confined in vertically coupled type II quantum dots with different morphologies in the presence of the external magnetic field is studied. The effect of the quantum dot morphology on the curves of the lowest energy levels as functions of the magnetic field is analyzed. It is shown that a strong correlation presented in this system generates the Aharonov-Bohm oscillations of the lower energy levels similar to those in wide quantum ring. The novel curves of the trion energies dependences on the external magnetic field for the disk-like, lens-like, and cone-like structures are presented.
Joe, Yong S; Lee, Sun H; Hedin, Eric R; Kim, Young D
2013-06-01
We utilize a two-dimensional four-channel DNA model, with a tight-binding (TB) Hamiltonian, and investigate the temperature and the magnetic field dependence of the transport behavior of a short DNA molecule. Random variation of the hopping integrals due to the thermal structural disorder, which partially destroy phase coherence of electrons and reduce quantum interference, leads to a reduction of the localization length and causes suppressed overall transmission. We also incorporate a variation of magnetic field flux density into the hopping integrals as a phase factor and observe Aharonov-Bohm (AB) oscillations in the transmission. It is shown that for non-zero magnetic flux, the transmission zero leaves the real-energy axis and moves up into the complex-energy plane. We also point out that the hydrogen bonds between the base pair with flux variations play a role to determine the periodicity of AB oscillations in the transmission. PMID:23862423
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.
Topological Charge Screening in Disordered Aharonov-Bohm Wavefunctions
NASA Astrophysics Data System (ADS)
Houston, Alexander; Hannay, John; Taylor, Alexander; Dennis, Mark
Free electrical charges are typically subject to screening relations. For example, in ionic fluids and Coulomb gases there is screening (both global and local) of the electrical charges, described by the first and second Stillinger-Lovett sum rules. A topological analogy governs the statistical behaviour of the nodal points in Gaussian random superpositions of plane waves. These nodal points are integer topological charges, i.e. vortices and antivortices of the complex wavefunction, whose sign is that of the phase circulation. Such superpositions are known to model high energy eigenfunctions in the presence of wave chaos, and display topological charge screening in the bulk. We investigate how these screening relations are affected by the introduction of a magnetic flux line, which may be fractional in strength. We find that the global screening relation is broken, with the average total topological charge of the vortices given by the flux strength, and that the local screening of the flux itself shows unexpected features.
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.
Impurity effects on energy levels and far-infrared spectra of nanorings
NASA Astrophysics Data System (ADS)
Hui, Pan; Jia-Lin, Zhu
2003-11-01
The effects of a positively charged impurity on the energy levels and far-infrared spectra of one and two electrons in semiconductor nanorings under magnetic fields are studied. The effects of the nanoring size and the impurity position are also discussed. It is shown that the electron-electron interaction and electron-impurity one in nanorings are strongly dependent on the nanoring size and the impurity position. Based on the studies of the impurity and field effects, the impurity-induced Aharonov-Bohm oscillations of the far-infrared spectra are found. The results predict a possibility of observing phenomena related to electron-impurity interaction in a nanoring in the future.
Effect of a magnetic flux line on the quantum beats in the Henon-Heiles level density.
Brack, M.; Bhaduri, R. K.; Law, J.; Maier, Ch.; Murthy, M. V. N.
1995-03-01
The quantum density of states of the Henon-Heiles potential displays a pronounced beating pattern. This has been explained by the interference of three isolated classical periodic orbits with nearby actions and periods. A singular magnetic flux line, passing through the origin, drastically alters the beats even though the classical Lagrangian equations of motion remain unchanged. Some of the changes can be easily understood in terms of the Aharonov-Bohm effect. However, we find that the standard periodic orbit theory does not reproduce the diffraction-like quantum effects on those classical orbits which intersect the singular flux line, and argue that corrections of relative order variant Planck's over 2pi are necessary to describe these effects. We also discuss the changes in the distribution of nearest-neighbor spacings in the eigenvalue spectrum, brought about by the flux line. (c) 1995 American Institute of Physics. PMID:12780185
Experimental realization of strong effective magnetic fields in an optical lattice.
Aidelsburger, M; Atala, M; Nascimbène, S; Trotzky, S; Chen, Y-A; Bloch, I
2011-12-16
We use Raman-assisted tunneling in an optical superlattice to generate large tunable effective magnetic fields for ultracold atoms. When hopping in the lattice, the accumulated phase shift by an atom is equivalent to the Aharonov-Bohm phase of a charged particle exposed to a staggered magnetic field of large magnitude, on the order of 1 flux quantum per plaquette. We study the ground state of this system and observe that the frustration induced by the magnetic field can lead to a degenerate ground state for noninteracting particles. We provide a measurement of the local phase acquired from Raman-induced tunneling, demonstrating time-reversal symmetry breaking of the underlying Hamiltonian. Furthermore, the quantum cyclotron orbit of single atoms in the lattice exposed to the magnetic field is directly revealed. PMID:22243087
NASA Astrophysics Data System (ADS)
Ansari, R.; Faghihnasiri, M.; Malakpour, S.; Sahmani, S.
2015-07-01
In the current investigation, ab initio calculations are performed to explore the influence of electric field on the mechanical properties of bilayer boron nitride with AB stacking order (AB-2LBN). To accomplish this, density functional theory (DFT) within the framework of generalized gradient approximation (GGA) is implemented. It is demonstrated that the electric field has significant effects on Young's modulus and Poisson's ratio of AB-2LBN when its magnitude is small. With increasing the magnitude of electric field, these effects diminish so that the mechanical properties with and without considering the electric field become approximately identical. Also, it is shown that the equilibrium strain energy decreases linearly by increasing the magnitude of applied electric field.
Two Further Experiments on Electron Interference
ERIC Educational Resources Information Center
Matteucci, G.; Pozzi, G.
1978-01-01
Presents the results of two experiments concerning the phenomena of the interference of probabilities and of the so called Aharonov-Bohm effect. An electron biprism and a standard electron microscope have been used for the experiments. (Author/GA)
Poniedziałek, M R; Szafran, B
2012-02-29
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. PMID:22277600
Quantum mechanics : Intellectually delicious;
Peshkin, M.; Vaidman, L.
2010-03-01
It is 50 years since the discovery of the Aharonov-Bohm effect, and 25 years since that of the Berry phase. A celebration of this double anniversary at the University of Bristol made evident that these discoveries still offer much food for thought. The meeting celebrating the fiftieth anniversary of the Aharonov-Bohm effect and the twenty-fifth anniversary of the Berry phase was held on 14-15 December 2009 in the historic H. H.
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.
Coulomb-interaction effects on the electronic structure of radially polarized excitons in nanorings
NASA Astrophysics Data System (ADS)
Barticevic, Z.; Pacheco, M.; Simonin, J.; Proetto, C. R.
2006-04-01
The electronic structure of radially polarized excitons in structured nanorings is analyzed, with emphasis in the ground-state properties and their dependence under applied magnetic fields perpendicular to the ring plane. The electron-hole Coulomb attraction has been treated rigorously, through numerical diagonalization of the full exciton Hamiltonian in the noninteracting electron-hole pairs basis. Depending on the relative weight of the kinetic energy and Coulomb contributions, the ground-state of polarized excitons has “extended” or “localized” features. In the first case, corresponding to small rings dominated by the kinetic energy, the ground-state shows Aharonov-Bohm (AB) oscillations due to the individual orbits of the building particles of the exciton. In the localized regime, corresponding to large rings dominated by the Coulomb interaction, the only remaining AB oscillations are due to the magnetic flux trapped between the electron and hole orbits. This dependence of the exciton, a neutral excitation, on the flux difference confirms this feature as a signature of Coulomb dominated polarized excitons. Analytical approximations are provided in both regimes, which accurately reproduce the numerical results.
Ab initio effective interactions for s d -shell valence nucleons
NASA Astrophysics Data System (ADS)
Dikmen, E.; Lisetskiy, A. F.; Barrett, B. R.; Maris, P.; Shirokov, A. M.; Vary, J. P.
2015-06-01
We perform ab initio no-core shell-model calculations for A =18 and 19 nuclei in a 4 ℏ Ω , or Nmax=4 , model space by using the effective JISP16 and chiral N3LO nucleon-nucleon potentials and transform the many-body effective Hamiltonians into the 0 ℏ Ω model space to construct the A -body effective Hamiltonians in the s d shell. We separate the A -body effective Hamiltonians with A =18 and A =19 into inert core, one-, and two-body components. Then we use these core, one-, and two-body components to perform standard shell-model calculations for the A =18 and A =19 systems with valence nucleons restricted to the s d shell. Finally, we compare the standard shell-model results in the 0 ℏ Ω model space with the exact no-core shell-model results in the 4 ℏ Ω model space for the A =18 and A =19 systems and find good agreement.
Ab initio modeling of the motional Stark effect on MAST
De Bock, M. F. M.; Conway, N. J.; Walsh, M. J.; Carolan, P. G.; Hawkes, N. C.
2008-10-15
A multichord motional Stark effect (MSE) system has recently been built on the MAST tokamak. In MAST the {pi} and {sigma} lines of the MSE spectrum overlap due to the low magnetic field typical for present day spherical tokamaks. Also, the field curvature results in a large change in the pitch angle over the observation volume. The measured polarization angle does not relate to one local pitch angle but to an integration over all pitch angles in the observation volume. The velocity distribution of the neutral beam further complicates the measurement. To take into account volume effects and velocity distribution, an ab initio code was written that simulates the MSE spectrum on MAST. The code is modular and can easily be adjusted for other tokamaks. The code returns the intensity, polarized fraction, and polarization angle as a function of wavelength. Results of the code are presented, showing the effect on depolarization and wavelength dependence of the polarization angle. The code is used to optimize the design and calibration of the MSE diagnostic.
Technology Transfer Automated Retrieval System (TEKTRAN)
Non-target effects of Cry1Ab x CP4 EPSPS and Cry1Ab + Cry3Bb1 x CP4 EPSPS Bt transgenic new maize hybrids on insidious flower bugs [Orius insidiosus (Say)] was studied in Nebraska (Mead, C lay Center, and Concord) during 2007 and 2008. The Bt effect was compared to CP4 EPSPS maize (isoline), convent...
Scaling of Aharonov-Bohm couplings and the dynamical vacuum in gauge theories
Goldhaber, A.S. ); Li, H. ); Parwani, R.R. )
1995-01-15
Recent results on the vacuum polarization induced by a thin string of magnetic flux lead us to suggest an analogue of the Copenhagen flux spaghetti'' QCD vacuum as a possible mechanism for avoiding the divergence of perturbative QED, thus permitting a consistent completion of the full, nonperturbative theory. The mechanism appears to operate for spinor, but not scalar, QED.
Deletion of nfnAB in Thermoanaerobacterium saccharolyticum and Its Effect on Metabolism
Lo, Jonathan; Zheng, Tianyong; Olson, Daniel G.; Ruppertsberger, Natalie; Tripathi, Shital A.; Guss, Adam M.; Lynd, Lee R.
2015-06-29
NfnAB catalyzes the reversible transfer of electrons from reduced ferredoxin and NADH to 2 NADP^{+}. The NfnAB complex has been hypothesized to be the main enzyme for ferredoxin oxidization in strains of Thermoanaerobacterium saccharolyticum engineered for increased ethanol production. NfnAB complex activity was detectable in crude cell extracts of T. saccharolyticum. In this paper, activity was also detected using activity staining of native PAGE gels. The nfnAB gene was deleted in different strains of T. saccharolyticum to determine its effect on end product formation. In wild-type T. saccharolyticum, deletion of nfnAB resulted in a 46% increase in H_{2} formation but otherwise little change in other fermentation products. In two engineered strains with 80% theoretical ethanol yield, loss of nfnAB caused two different responses: in one strain, ethanol yield decreased to about 30% of the theoretical value, while another strain had no change in ethanol yield. Biochemical analysis of cell extracts showed that the ΔnfnAB strain with decreased ethanol yield had NADPH-linked alcohol dehydrogenase (ADH) activity, while the ΔnfnAB strain with unchanged ethanol yield had NADH-linked ADH activity. Deletion of nfnAB caused loss of NADPH-linked ferredoxin oxidoreductase activity in all cell extracts. Significant NADH-linked ferredoxin oxidoreductase activity was seen in all cell extracts, including those that had lost nfnAB. This suggests that there is an unidentified NADH:ferredoxin oxidoreductase (distinct from nfnAB) playing a role in ethanol formation. The NfnAB complex plays a key role in generating NADPH in a strain that had become reliant on NADPH-ADH activity. Importance: Thermophilic anaerobes that can convert biomass-derived sugars into ethanol have been investigated as candidates for biofuel formation. Many anaerobes have been genetically engineered to increase biofuel formation; however, key aspects of metabolism remain unknown and poorly
Deletion of nfnAB in Thermoanaerobacterium saccharolyticum and Its Effect on Metabolism
Lo, Jonathan; Zheng, Tianyong; Olson, Daniel G.; Ruppertsberger, Natalie; Tripathi, Shital A.; Guss, Adam M.
2015-01-01
ABSTRACT NfnAB catalyzes the reversible transfer of electrons from reduced ferredoxin and NADH to 2 NADP+. The NfnAB complex has been hypothesized to be the main enzyme for ferredoxin oxidization in strains of Thermoanaerobacterium saccharolyticum engineered for increased ethanol production. NfnAB complex activity was detectable in crude cell extracts of T. saccharolyticum. Activity was also detected using activity staining of native PAGE gels. The nfnAB gene was deleted in different strains of T. saccharolyticum to determine its effect on end product formation. In wild-type T. saccharolyticum, deletion of nfnAB resulted in a 46% increase in H2 formation but otherwise little change in other fermentation products. In two engineered strains with 80% theoretical ethanol yield, loss of nfnAB caused two different responses: in one strain, ethanol yield decreased to about 30% of the theoretical value, while another strain had no change in ethanol yield. Biochemical analysis of cell extracts showed that the ΔnfnAB strain with decreased ethanol yield had NADPH-linked alcohol dehydrogenase (ADH) activity, while the ΔnfnAB strain with unchanged ethanol yield had NADH-linked ADH activity. Deletion of nfnAB caused loss of NADPH-linked ferredoxin oxidoreductase activity in all cell extracts. Significant NADH-linked ferredoxin oxidoreductase activity was seen in all cell extracts, including those that had lost nfnAB. This suggests that there is an unidentified NADH:ferredoxin oxidoreductase (distinct from nfnAB) playing a role in ethanol formation. The NfnAB complex plays a key role in generating NADPH in a strain that had become reliant on NADPH-ADH activity. IMPORTANCE Thermophilic anaerobes that can convert biomass-derived sugars into ethanol have been investigated as candidates for biofuel formation. Many anaerobes have been genetically engineered to increase biofuel formation; however, key aspects of metabolism remain unknown and poorly understood. One example is the
Deletion of nfnAB in Thermoanaerobacterium saccharolyticum and Its Effect on Metabolism
Lo, Jonathan; Zheng, Tianyong; Olson, Daniel G.; Ruppertsberger, Natalie; Tripathi, Shital A.; Guss, Adam M.; Lynd, Lee R.
2015-06-29
NfnAB catalyzes the reversible transfer of electrons from reduced ferredoxin and NADH to 2 NADP+. The NfnAB complex has been hypothesized to be the main enzyme for ferredoxin oxidization in strains of Thermoanaerobacterium saccharolyticum engineered for increased ethanol production. NfnAB complex activity was detectable in crude cell extracts of T. saccharolyticum. In this paper, activity was also detected using activity staining of native PAGE gels. The nfnAB gene was deleted in different strains of T. saccharolyticum to determine its effect on end product formation. In wild-type T. saccharolyticum, deletion of nfnAB resulted in a 46% increase in H2 formation butmore » otherwise little change in other fermentation products. In two engineered strains with 80% theoretical ethanol yield, loss of nfnAB caused two different responses: in one strain, ethanol yield decreased to about 30% of the theoretical value, while another strain had no change in ethanol yield. Biochemical analysis of cell extracts showed that the ΔnfnAB strain with decreased ethanol yield had NADPH-linked alcohol dehydrogenase (ADH) activity, while the ΔnfnAB strain with unchanged ethanol yield had NADH-linked ADH activity. Deletion of nfnAB caused loss of NADPH-linked ferredoxin oxidoreductase activity in all cell extracts. Significant NADH-linked ferredoxin oxidoreductase activity was seen in all cell extracts, including those that had lost nfnAB. This suggests that there is an unidentified NADH:ferredoxin oxidoreductase (distinct from nfnAB) playing a role in ethanol formation. The NfnAB complex plays a key role in generating NADPH in a strain that had become reliant on NADPH-ADH activity. Importance: Thermophilic anaerobes that can convert biomass-derived sugars into ethanol have been investigated as candidates for biofuel formation. Many anaerobes have been genetically engineered to increase biofuel formation; however, key aspects of metabolism remain unknown and poorly understood. One
Zeeman effect on surface electron transport in topological insulator Bi2Se3 nanoribbons
NASA Astrophysics Data System (ADS)
Wang, Li-Xian; Yan, Yuan; Zhang, Liang; Liao, Zhi-Min; Wu, Han-Chun; Yu, Da-Peng
2015-10-01
Topological insulators have exotic surface states that are massless Dirac fermions, manifesting special magnetotransport properties, such as the Aharonov-Bohm effect, Shubnikov-de Haas oscillations, and weak antilocalization effects. In the surface Dirac cone, the band structures are typically closely related to the p-orbitals and possess helical orbital texture. Here we report on the tunability of the transport properties via the interaction between the magnetic field and the spin-orbital angular momentum of the surface states in individual Bi2Se3 nanoribbons. Because the surface states have a large Landé factor and helical spin-orbital texture, the in-plane magnetic field induced Zeeman energy will result in the deformation of the Dirac cone, which gives rise to spin polarization of the surface states. The spin-dependent scattering of the conducting electrons on the existing local magnetic moments produces a giant negative magnetoresistance. The negative magnetoresistance is robust with a ratio of -20% at 2 K and -0.5% at 300 K under 14 T. The results are valuable for possible orbital-electronics based on topological insulators.Topological insulators have exotic surface states that are massless Dirac fermions, manifesting special magnetotransport properties, such as the Aharonov-Bohm effect, Shubnikov-de Haas oscillations, and weak antilocalization effects. In the surface Dirac cone, the band structures are typically closely related to the p-orbitals and possess helical orbital texture. Here we report on the tunability of the transport properties via the interaction between the magnetic field and the spin-orbital angular momentum of the surface states in individual Bi2Se3 nanoribbons. Because the surface states have a large Landé factor and helical spin-orbital texture, the in-plane magnetic field induced Zeeman energy will result in the deformation of the Dirac cone, which gives rise to spin polarization of the surface states. The spin-dependent scattering of
Andreassen, M; Bøhn, T; Wikmark, O-G; Van den Berg, J; Løvik, M; Traavik, T; Nygaard, U C
2015-03-01
The genetically modified (GM) maize event MON810 has been inserted with a processed version of the transgene, cry1Ab, derived from the soil bacterium Bacillus thuringiensis (Bt) to express proteins with insecticidal properties. Such proteins may introduce new allergens and also act as adjuvants that promote allergic responses. While focus has been on safe consumption and hence the oral exposure to GM food and feed, little is known regarding inhalation of pollen and desiccated airborne plant material from GM crops. The aim of this study was to investigate whether plant material from the Cry1Ab-expressing maize variety MON810, or trypsin-activated Cry1Ab (trypCry1Ab) protein produced in recombinant bacteria, may act as adjuvants against the allergen ovalbumin (OVA) in a mouse model of airway allergy. A clear proallergic adjuvant effect of the mucosal adjuvant cholera toxin (CT) was demonstrated, determined as increased specific IgE, eosinophils and Th2 cytokines in MLN cell supernates, while no elevation in OVA-specific antibodies or cytokine release from MLN cells after stimulation with OVA were observed in mice receiving Cry1Ab-containing plant materials or the trypCry1Ab protein. Our data suggest that Cry1Ab proteins had no detectable systemic adjuvant effect in mice after airway exposure. Further experiments with purified plant proteins, as well as long-term exposures needs be conducted to further evaluate exposures experienced in real-life situations. PMID:25564738
Effects of Cry1F and Cry34Ab1/35Ab1 on storage pests
Technology Transfer Automated Retrieval System (TEKTRAN)
Two crystalline protoxins from Bacillus thuringiensis (Bt), Cry1Fa1 and Cry34Ab1/Cry35Ab1 (Cry1F, Cry34/35), were evaluated for efficacy against lepidopteran and coleopteran storage pests. Cry1F was tested against the lepidopterans Sitotroga cerealella (Angoumois grain moth) and colonies of the lep...
NASA Astrophysics Data System (ADS)
Wu, Dianxing; Ye, Qingfu; Wang, Zhonghua; Xia, Yingwu
2004-01-01
The effects of gamma irradiation on the transgenic rice containing a synthetic cry1Ab gene from Bacillus thuringiensis were investigated. There was almost no difference in the content of the major nutritional components, i.e. crude protein, crude lipid, eight essential amino acids and total ash between the irradiated grains and the non-irradiated transgenic rice. However, the amounts of Cry1Ab protein and apparent amylose in the irradiated transgenic rice were reduced significantly by the doses higher than 200 Gy. In vivo observation showed that Cry1Ab protein contents also decreased in the fresh leaf tissues of survival seedlings after irradiation with 200 Gy or higher doses and showed inhibition of seedling growth. The results indicate that gamma irradiation might improve the quality of transgenic rice due to removal of the toxic Cry1Ab protein.
Madliger, Michael; Gasser, Christoph A; Schwarzenbach, René P; Sander, Michael
2011-05-15
Bt crops are genetically modified to be resistant against insect pests by expressing insecticidal Cry proteins. The processes governing the fate and bioavailability of the expressed transgenic Cry proteins in soils are poorly understood. We studied adsorption of Cry1Ab to negatively charged silica (SiO(2)) particles, a major soil constituent and a model for negatively charged mineral surfaces, at pH 5 to 10 and ionic strengths I = 10 mM to 250 mM, both in solution depletion and saturated column transport experiments. Cry1Ab-SiO(2) interactions were dominated by patch-controlled electrostatic attraction (PCEA), as evident from increasing Cry1Ab attraction to SiO(2) with decreasing I at pH at which both Cry1Ab and SiO(2) were net negatively charged. Experimental and modeling evidence is provided that the surface heterogeneity of SiO(2) particles modulated PCEA, leading to a fraction of adsorption sites with slow Cry1Ab desorption kinetics. Desorption rates from these sites increased upon increasing the solution pH. In toxicity bioassays, we demonstrated that Cry1Ab retained insecticidal activity when adsorbed to SiO(2), suggesting high protein conformational stability during adsorption-desorption cycles. Models predicting Cry1A protein adsorption in soils therefore need to account for combined effects of the nonuniform protein surface charge distribution and of sorbent surface heterogeneity. PMID:21526821
Robust electron pairing in the integer quantum hall effect regime.
Choi, H K; Sivan, I; Rosenblatt, A; Heiblum, M; Umansky, V; Mahalu, D
2015-01-01
Electron pairing is a rare phenomenon appearing only in a few unique physical systems; for example, superconductors and Kondo-correlated quantum dots. Here, we report on an unexpected electron pairing in the integer quantum Hall effect regime. The pairing takes place within an interfering edge channel in an electronic Fabry-Perot interferometer at a wide range of bulk filling factors, between 2 and 5. We report on three main observations: high-visibility Aharonov-Bohm conductance oscillations with magnetic flux periodicity equal to half the magnetic flux quantum; an interfering quasiparticle charge equal to twice the elementary electron charge as revealed by quantum shot noise measurements, and full dephasing of the pairs' interference by induced dephasing of the adjacent inner edge channel-a manifestation of inter-channel entanglement. Although this pairing phenomenon clearly results from inter-channel interaction, the exact mechanism that leads to electron-electron attraction within a single edge channel is not clear. We believe that substantial efforts are needed in order to clarify these intriguing and unexpected findings. PMID:26096516
Magnetic doping and kondo effect in bi(2)se(3) nanoribbons.
Cha, Judy J; Williams, James R; Kong, Desheng; Meister, Stefan; Peng, Hailin; Bestwick, Andrew J; Gallagher, Patrick; Goldhaber-Gordon, David; Cui, Yi
2010-03-10
A simple surface band structure and a large bulk band gap have allowed Bi2Se3 to become a reference material for the newly discovered three-dimensional topological insulators, which exhibit topologically protected conducting surface states that reside inside the bulk band gap. Studying topological insulators such as Bi2Se3 in nanostructures is advantageous because of the high surface-to-volume ratio, which enhances effects from the surface states; recently reported Aharonov-Bohm oscillation in topological insulator nanoribbons by some of us is a good example. Theoretically, introducing magnetic impurities in topological insulators is predicted to open a small gap in the surface states by breaking time-reversal symmetry. Here, we present synthesis of magnetically doped Bi2Se3 nanoribbons by vapor-liquid-solid growth using magnetic metal thin films as catalysts. Although the doping concentration is less than approximately 2%, low-temperature transport measurements of the Fe-doped Bi2Se3 nanoribbon devices show a clear Kondo effect at temperatures below 30 K, confirming the presence of magnetic impurities in the Bi2Se3 nanoribbons. The capability to dope topological insulator nanostructures magnetically opens up exciting opportunities for spintronics. PMID:20131918
Zeeman effect on surface electron transport in topological insulator Bi2Se3 nanoribbons.
Wang, Li-Xian; Yan, Yuan; Zhang, Liang; Liao, Zhi-Min; Wu, Han-Chun; Yu, Da-Peng
2015-10-28
Topological insulators have exotic surface states that are massless Dirac fermions, manifesting special magnetotransport properties, such as the Aharonov-Bohm effect, Shubnikov-de Haas oscillations, and weak antilocalization effects. In the surface Dirac cone, the band structures are typically closely related to the p-orbitals and possess helical orbital texture. Here we report on the tunability of the transport properties via the interaction between the magnetic field and the spin-orbital angular momentum of the surface states in individual Bi2Se3 nanoribbons. Because the surface states have a large Landé factor and helical spin-orbital texture, the in-plane magnetic field induced Zeeman energy will result in the deformation of the Dirac cone, which gives rise to spin polarization of the surface states. The spin-dependent scattering of the conducting electrons on the existing local magnetic moments produces a giant negative magnetoresistance. The negative magnetoresistance is robust with a ratio of -20% at 2 K and -0.5% at 300 K under 14 T. The results are valuable for possible orbital-electronics based on topological insulators. PMID:26400635
NASA Astrophysics Data System (ADS)
Moulopoulos, K.
2015-06-01
A quantum system that lies nearby a magnetic or time-varying electric field region, and that is under periodic boundary conditions parallel to the interface, is shown to exhibit a "hidden" Aharonov-Bohm effect (magnetic or electric), caused by fluxes that are not enclosed by, but are merely neighboring to our system - its origin being the absence of magnetic monopoles in 3D space (with corresponding spacetime generalizations). Novel possibilities then arise, where a field-free system can be dramatically affected by manipulating fields in an adjacent or even distant land, provided that these nearby fluxes are not quantized (i.e. they are fractional or irrational parts of the flux quantum). Topological effects (such as Quantum Hall types of behaviors) can therefore be induced from outside our system (that is always field-free and can even reside in simply-connected space). Potential novel applications are outlined, and exotic consequences in solid state physics are pointed out (i.e. the possibility of field-free quantum periodic systems that violate Bloch's theorem), while formal analogies with certain high energy physics phenomena and with some rather under-explored areas in mechanics and thermodynamics are noted.
Resonant Transmission through Serially Connected Hexagonal Nanorings with Magnetic Flux Effects
NASA Astrophysics Data System (ADS)
Hedin, Eric; Joe, Yong
Nanostructures composed of six quantum dots (QDs) connected in a ring are linked together in a linear chain with each ring separated by a coupling segment from adjoining rings. A tight-binding model is used to obtain the electron transmission through an arbitrary number of rings in series as a function of energy, external magnetic field, coupling parameters, and QD site energy values. Modifications of the transmission band structure as a function of external field, due to the Aharonov-Bohm and Zeeman effects, demonstrate control over the conductance properties of the linear chain of nano-rings. Resonant transmission effects (with electron energy equal to the QD site energy values) show a complex dependence upon an interplay of magnetic flux, inter-ring coupling, and the strength of the coupling between the ring system and the external leads. For specific values of lead and ring couplings, nearly full transmission (ballistic transport) is seen to occur across a broad energy range, independent of the number of rings in series. Partially supported by BSU ASPiRE program.
Quantum-interference effects in single- and poly-crystalline topological insulator Bi2-xTe3
NASA Astrophysics Data System (ADS)
Chiu, Shao-Pin; Lin, Juhn-Jong
2014-03-01
We have studied the carrier transport properties of both single- and poly-crystalline topological insulator (TI) Bi2-xTe3 samples. Single-crystalline microflakes were made by exfoliation from a single-crystalline Bi2Te3 bulk. Polycrystalline samples were made by flash evaporation of 5N purity Bi2Te3 sheets. In single-crystalline Bi2Te3 microflakes, temperature dependent resistances revealed two-dimensional (2D) electron-electron interaction effect. The extracted Coulomb screening parameter is negative, in accord with the situation of strong spin-orbit coupling in the TI materials. Positive magnetoresistances (MRs) originated from 2D weak-antilocalization (WAL) effect were measured in low magnetic fields, and satisfactorily described by a multichannel-conduction model. Especially, as T below 1 K and under high positive backgate voltages, signature of two coherent conduction channels was found. We discuss our results in terms of Dirac fermion states on the bottom surface, in addition to the bulk states. Polycrystalline Bi2-xTe3 thin films were patterned by electron-beam lithography. In low perpendicular magnetic fields, positive MRs due to the 2D WAL effect were observed. In parallel magnetic fields, Aharonov-Bohm oscillations were measured, suggesting the presence of metallic surface states. This work was supported by the Taiwan National Science Council through Grant No. NSC102-2120-M-009-003 (J.J.L.).
AB40. Sexual side effects of medical treatment of BPH
Park, Hyun Jun
2014-01-01
The medical and surgical management of BPH/LUTS can affect erectile function (EF), cause ejaculatory dysfunction (EjD) or affect libido. Five alpha reductase inhibitors, such as finasteride and dutasteride have good efficacy for benign prostatic hyperplasia, however they have also sexual side effects including loss of libido, erectile dysfunction and decreased ejaculatory volume. Also, alpha adrenergic blockers are well known and standard medical treatment options for BPH/LUTS, and in spite of their high efficacy and low adverse effects, retrograde and diminished ejaculation are potential sexual side effects. Although the prevalence of five alpha reductase inhibitors and alpha adrenergic blockers are not high, their impact on the patients’ quality of life must be regarded as important as their efficacy for BPH/LUTS. This lecture will review the effects of these therapies on sexual function.
NASA Astrophysics Data System (ADS)
Jauregui, Luis A.; Pettes, Michael T.; Shi, Li; Rokhinson, Leonid P.; Chen, Yong P.
2014-03-01
Topological superconductivity can be proximity induced by coupling s-wave superconductors with spin-helical electron systems, such as the surface of 3D topological insulators (TIs), where the energy bands follow Dirac dispersion and the electronic states possess helical spin-momentum locking. We have grown Bi2Te3 nanoribbons (NRs) by vapor liquid solid method and characterized their crystalline structure by TEM and Raman spectroscopy. We fabricate backgated field effect devices where the chemical potential (μ) can be tuned from bulk bands to surface states and ambipolar field effect has been observed. The temperature dependence of the resistance and Shubnikov de Haas oscillations show suppressed bulk conduction with surface conduction dominating and a pi-Berry's phase. The Aharonov-Bohm oscillations (ABO), measured with a magnetic field parallel to the NR axis, have a period equal to one flux quanta with conductance maxima at half flux quanta (pi-ABO), for μ close to the charge neutrality point. Such pi-ABO is a direct evidence of the existence of 1D helical modes at half flux quanta. We have also fabricated Josephson junctions on our TI NR devices with inter-electrode separations up to 200 nm, and measured supercurrent with a proximity induced gap of 0.5meV at 0.25K.
Marusich, Julie A.; Lefever, Timothy W.; Antonazzo, Kateland R.; Wallgren, Michael T.; Cortes, Ricardo A.; Patel, Purvi R.; Grabenauer, Megan; Moore, Katherine N.
2015-01-01
Diversion of synthetic cannabinoids for abuse began in the early 2000s. Despite legislation banning compounds currently on the drug market, illicit manufacturers continue to release new compounds for recreational use. This study examined new synthetic cannabinoids, AB-CHMINACA (N-[1-amino-3-methyl-oxobutan-2-yl]-1-[cyclohexylmethyl]-1H-indazole-3-carboxamide), AB-PINACA [N-(1-amino-3-methyl-1-oxobutan-2-yl)-1-pentyl-1H-indazole-3-carboxamide], and FUBIMINA [(1-(5-fluoropentyl)-1H-benzo[d]imadazol-2-yl)(naphthalen-1-yl)methanone], with the hypothesis that these compounds, like those before them, would be highly susceptible to abuse. Cannabinoids were examined in vitro for binding and activation of CB1 receptors, and in vivo for pharmacological effects in mice and in Δ9-tetrahydrocannabinol (Δ9-THC) discrimination. AB-CHMINACA, AB-PINACA, and FUBIMINA bound to and activated CB1 and CB2 receptors, and produced locomotor suppression, antinociception, hypothermia, and catalepsy. Furthermore, these compounds, along with JWH-018 [1-pentyl-3-(1-naphthoyl)indole], CP47,497 [rel-5-(1,1-dimethylheptyl)-2-[(1R,3S)-3-hydroxycyclohexyl]-phenol], and WIN55,212-2 ([(3R)-2,3-dihydro-5-methyl-3-(4-morpholinylmethyl)pyrrolo[1,2,3-de]-1,4-benzoxazin-6-yl]-1-naphthalenyl-methanone, monomethanesulfonate), substituted for Δ9-THC in Δ9-THC discrimination. Rank order of potency correlated with CB1 receptor-binding affinity, and all three compounds were full agonists in [35S]GTPγS binding, as compared with the partial agonist Δ9-THC. Indeed, AB-CHMINACA and AB-PINACA exhibited higher efficacy than most known full agonists of the CB1 receptor. Preliminary analysis of urinary metabolites of the compounds revealed the expected hydroxylation. AB-PINACA and AB-CHMINACA are of potential interest as research tools due to their unique chemical structures and high CB1 receptor efficacies. Further studies on these chemicals are likely to include research on understanding cannabinoid receptors
Ab initio study of piezomagnetic effect in Mn-antiperovskites
NASA Astrophysics Data System (ADS)
Sandeman, Karl; Gercsi, Zsolt; Zemen, Jan
2015-03-01
The magnetocaloric and magnetoelastic coupling that often occur together in magnetically frustrated materials have great potential for practical applications ranging from magnetic refrigeration to data processing and storage. Here we focus on the manganese antiperovskite family. Negative thermal expansion (NTE) close to the Néel temperature and a large magnetovolume effect have been measured recently in Mn3NiN using temperature dependent neutron powder diffraction. A large piezomagnetic effect has been predicted in Mn3GaN from Density Functional Theory (DFT) calculations. We perform a computational study of the piezomagnetic effect in three metallic Mn3XN antiperovskites, based our recent DFT model of anisotropic thermal expansions and large magnetoelastic coupling. We confirm the existence of a fully compensated non-collinear antiferromagnetic ground state and predict canting and the change of magnitude of the Mn local magnetic moments as a function of applied biaxial strain, finding that the induced net magnetization reaches values of 0.1 μB per Mn per 1% of strain. The research leading to these results has received funding from the European Community's 7th Framework Programme under Grant agreement 310748 ``DRREAM.''
Toward ab initio DFT: Pairing and Optimized Effective Potential
NASA Astrophysics Data System (ADS)
Drut, Joaquin
2010-11-01
The quest for a universal nuclear energy density functional has stimulated research in many different areas of quantum many-body physics. Advances in the last decade have enabled quantum chemists to explicitly construct energy density functionals for the Coulomb interaction from first principles. This task was accomplished by extending the notion of density-dependent functionals to include explicit dependence on the Kohn-Sham orbitals. The resulting approach is usually called the Optimized Effective Potential (OEP). Are these developments useful in the nuclear case? Can one extend the OEP to include pairing? In this contribution we present some first answers to these and other related questions.
NASA Astrophysics Data System (ADS)
Timko, Jeff; Kuyucak, Serdar
2012-11-01
Polarization is an important component of molecular interactions and is expected to play a particularly significant role in inhomogeneous environments such as pores and interfaces. Here we investigate the effects of polarization in the gramicidin A ion channel by performing quantum mechanics/molecular mechanics molecular dynamics (MD) simulations and comparing the results with those obtained from classical MD simulations with non-polarizable force fields. We consider the dipole moments of backbone carbonyl groups and channel water molecules as well as a number of structural quantities of interest. The ab initio results show that the dipole moments of the carbonyl groups and water molecules are highly sensitive to the hydrogen bonds (H-bonds) they participate in. In the absence of a K+ ion, water molecules in the channel are quite mobile, making the H-bond network highly dynamic. A central K+ ion acts as an anchor for the channel waters, stabilizing the H-bond network and thereby increasing their average dipole moments. In contrast, the K+ ion has little effect on the dipole moments of the neighboring carbonyl groups. The weakness of the ion-peptide interactions helps to explain the near diffusion-rate conductance of K+ ions through the channel. We also address the sampling issue in relatively short ab initio MD simulations. Results obtained from a continuous 20 ps ab initio MD simulation are compared with those generated by sampling ten windows from a much longer classical MD simulation and running each window for 2 ps with ab initio MD. Both methods yield similar results for a number of quantities of interest, indicating that fluctuations are fast enough to justify the short ab initio MD simulations.
Dynamic spin-flip shot noise of mesoscopic transport through a toroidal carbon nanotube
NASA Astrophysics Data System (ADS)
Zhao, H. K.; Zhang, J.; Wang, J.
2015-01-01
The shot noise in a toroidal carbon nanotube (TCN) interferometer under the perturbation of a rotating magnetic field (RMF) has been investigated. A general shot noise formula has been derived by calculating the current correlation. It was found that photon absorption and emission induce novel features of dynamic shot noise. The oscillatory behavior of shot noise and Fano factor vary with the Aharonov-Bohm (AB) magnetic flux, and they are sensitively dependent on the Zeeman energy, frequency of RMF, and source-drain bias. By adjusting the Zeeman energy, the AB oscillation structures of shot noise and Fano factor show valley-to-peak transformation. The shot noise increases nonlinearly with increasing the Zeeman energy and photon energy. The enhancement and asymmetry of shot noise can be attributed to the spin-flip effect.
Topological quantum scattering under the influence of a nontrivial boundary condition
NASA Astrophysics Data System (ADS)
Mota, Herondy
2016-04-01
We consider the quantum scattering problem of a relativistic particle in (2 + 1)-dimensional cosmic string spacetime under the influence of a nontrivial boundary condition imposed on the solution of the Klein-Gordon equation. The solution is then shifted as consequence of the nontrivial boundary condition and the role of the phase shift is to produce an Aharonov-Bohm-like effect. We examine the connection between this phase shift and the electromagnetic and gravitational analogous of the Aharonov-Bohm effect and compare the present results with previous ones obtained in the literature, also considering non-relativistic cases.
Ab initio investigation of light-induced relativistic spin-flip effects in magneto-optics
NASA Astrophysics Data System (ADS)
Mondal, Ritwik; Berritta, Marco; Carva, Karel; Oppeneer, Peter M.
2015-05-01
Excitation of a metallic ferromagnet such as Ni with an intensive femtosecond laser pulse causes an ultrafast demagnetization within approximately 300 fs. It was proposed that the ultrafast demagnetization measured in femtosecond magneto-optical experiments could be due to relativistic light-induced processes. We perform an ab initio investigation of the influence of relativistic effects on the magneto-optical response of Ni. To this end, first, we develop a response theory formulation of the additional appearing ultrarelativistic terms in the Foldy-Wouthuysen transformed Dirac Hamiltonian due to the electromagnetic field, and second, we compute the influence of relativistic light-induced spin-flip transitions on the magneto-optics. Our ab initio calculations of relativistic spin-flip optical excitations predict that these can give only a very small contribution (≤0.1 %) to the laser-induced magnetization change in Ni.
Topological effects in quantum mechanics
Peshkin, M.; Lipkin, H.J. |
1995-08-01
We completed our analysis of experiments, some completed, some planned, and some only conceptual at present, that purport to demonstrate new kinds of non-local and topological effects in the interaction of a neutron with an external electromagnetic field. In the Aharonov-Casher effect (AC), the neutron interacts with an electric field and in the Scalar Aharonov-Bohm effect (SAB) the neutron interacts with a magnetic field. In both cases, the geometry can be arranged so that there is no force on the neutron but an interference experiment nevertheless finds a phase shift proportional to the applied field and to the neutron`s magnetic moment. Previously, we showed that the accepted interpretation of these phenomena as topological effects due to a non-local interaction between the neutron and the electromagnetic field is incorrect. Both AC and SAB follow from local torques on the neutron whose expectation values vanish at every instant but which have non-vanishing effect on the measurable spin-correlation variables S(t) = (1/2) [{sigma}{sub x}{sigma}{sub x}(t) + {sigma}{sub y}(0){sigma}{sub y}(t) + h.c.] and V(t) = [{sigma}{sub x}(0){sigma}{sub y}(t) - {sigma}{sub y}(0){sigma}{sub x}(t) + h.c.]. We have now completed this work by observing that a criterion often used for identifying a topological effect, energy independence of the phase shift between two arms of an interferometer, is only a necessary condition, and by describing a phase shifter which obeys the energy-independence condition but whose interaction with the neutron is neither topological nor even non-local.
NASA Astrophysics Data System (ADS)
Ma, H.; Guo, S.; Hong, X.; Zhou, Y.
2015-05-01
The HJ-1A/B satellite offers free images with high spatial and temporal resolution, which are effective for dynamically monitoring cyanobacteria blooms. However, the HJ-1A/B satellite also receives distorted signals due to the influence of atmosphere. To acquire accurate information about cyanobacteria blooms, atmospheric correction is needed. HJ-1A/B images were atmosphere corrected using the FLAASH atmospheric correction model. Considering the quantum effect within a certain wavelength range, a spectral response function was included in the process. Then the model was used to process HJ-1A/B images, and the NDVI after atmospheric correction was compared with that before correction. The standard deviation improved from 0.13 to 0.158. Results indicate that atmospheric correction effectively reduces the distorted signals. Finally, NDVI was utilized to monitor the cyanobacteria bloom in Donghu Lake. The accuracy was enhanced compared with that before correction.
Quantum fluctuations and isotope effects in ab initio descriptions of water
Wang, Lu; Markland, Thomas E.; Ceriotti, Michele
2014-09-14
Isotope substitution is extensively used to investigate the microscopic behavior of hydrogen bonded systems such as liquid water. The changes in structure and stability of these systems upon isotope substitution arise entirely from the quantum mechanical nature of the nuclei. Here, we provide a fully ab initio determination of the isotope exchange free energy and fractionation ratio of hydrogen and deuterium in water treating exactly nuclear quantum effects and explicitly modeling the quantum nature of the electrons. This allows us to assess how quantum effects in water manifest as isotope effects, and unravel how the interplay between electronic exchange and correlation and nuclear quantum fluctuations determine the structure of the hydrogen bond in water.
Effect of composition on antiphase boundary energy in Ni3Al based alloys: Ab initio calculations
NASA Astrophysics Data System (ADS)
Gorbatov, O. I.; Lomaev, I. L.; Gornostyrev, Yu. N.; Ruban, A. V.; Furrer, D.; Venkatesh, V.; Novikov, D. L.; Burlatsky, S. F.
2016-06-01
The effect of composition on the antiphase boundary (APB) energy of Ni-based L 12-ordered alloys is investigated by ab initio calculations employing the coherent potential approximation. The calculated APB energies for the {111} and {001} planes reproduce experimental values of the APB energy. The APB energies for the nonstoichiometric γ' phase increase with Al concentration and are in line with the experiment. The magnitude of the alloying effect on the APB energy correlates with the variation of the ordering energy of the alloy according to the alloying element's position in the 3 d row. The elements from the left side of the 3 d row increase the APB energy of the Ni-based L 12-ordered alloys, while the elements from the right side slightly affect it except Ni. The way to predict the effect of an addition on the {111} APB energy in a multicomponent alloy is discussed.
Ab Initio Classical Dynamics Simulations of CO_2 Line-Mixing Effects in Infrared Bands
NASA Astrophysics Data System (ADS)
Lamouroux, Julien; Hartmann, Jean-Michel; Tran, Ha; Snels, Marcel; Stefani, Stefania; Piccioni, Giuseppe
2013-06-01
Ab initio calculations of line-mixing effects in CO_2 infrared bands are presented and compared with experiments. The predictions were carried using requantized Classical Dynamics Molecular Simulations (rCDMS) based on an approach previously developed and successfully tested for CO_2 isolated line shapes. Using classical dynamics equations, the force and torque applied to each molecule by the surrounding molecules (described by an ab initio intermolecular potential) are computed at each time step. This enables, using a requantization procedure, to predict dipole and isotropic polarizability auto-correlation functions whose Fourier-Laplace transforms yield the spectra. The quality of the rCDMS calculations is demonstrated by comparisons with measured spectra in the spectral regions of the 3ν_3 and 2ν_1+2ν_2+ν_3 Infrared bands. J.-M. Hartmann, H. Tran, N. H. Ngo, et al., Phys. Rev. Lett. A {87} (2013), 013403. H. Tran, C. Boulet, M. Snels, S. Stefani, J. Quant. Spectrosc. Radiat. Transfer {112} (2011), 925-936.
Ab initio molecular dynamics of solvation effects on reactivity at electrified interfaces.
Herron, Jeffrey A; Morikawa, Yoshitada; Mavrikakis, Manos
2016-08-23
Using ab initio molecular dynamics as implemented in periodic, self-consistent (generalized gradient approximation Perdew-Burke-Ernzerhof) density functional theory, we investigated the mechanism of methanol electrooxidation on Pt(111). We investigated the role of water solvation and electrode potential on the energetics of the first proton transfer step, methanol electrooxidation to methoxy (CH3O) or hydroxymethyl (CH2OH). The results show that solvation weakens the adsorption of methoxy to uncharged Pt(111), whereas the binding energies of methanol and hydroxymethyl are not significantly affected. The free energies of activation for breaking the C-H and O-H bonds in methanol were calculated through a Blue Moon Ensemble using constrained ab initio molecular dynamics. Calculated barriers for these elementary steps on unsolvated, uncharged Pt(111) are similar to results for climbing-image nudged elastic band calculations from the literature. Water solvation reduces the barriers for both C-H and O-H bond activation steps with respect to their vapor-phase values, although the effect is more pronounced for C-H bond activation, due to less disruption of the hydrogen bond network. The calculated activation energy barriers show that breaking the C-H bond of methanol is more facile than the O-H bond on solvated negatively biased or uncharged Pt(111). However, with positive bias, O-H bond activation is enhanced, becoming slightly more facile than C-H bond activation. PMID:27503889
NASA Astrophysics Data System (ADS)
Erba, A.
2014-09-01
A general-purpose, fully automated, computationally efficient implementation is presented of a series of techniques for the simultaneous description of pressure and temperature effects on structural properties of materials, by means of standard ab initio simulations. Equilibrium volume, bulk modulus, thermal expansion coefficient, equation-of-state, Grüneisen parameter, constant-pressure and constant-volume specific heats are computed as a function of temperature and pressure for the simple crystal of diamond and compared with accurate experimental data. Convergence of computed properties with respect to super-cell size is critically discussed. The effect on such properties of the adopted exchange-correlation functional of the density-functional-theory is discussed by considering three different levels of approximation (including hybrids): it is found to be rather small for the temperature dependence of equilibrium volume and bulk modulus, whereas it is quite large as regards their absolute values.
Erba, A
2014-09-28
A general-purpose, fully automated, computationally efficient implementation is presented of a series of techniques for the simultaneous description of pressure and temperature effects on structural properties of materials, by means of standard ab initio simulations. Equilibrium volume, bulk modulus, thermal expansion coefficient, equation-of-state, Grüneisen parameter, constant-pressure and constant-volume specific heats are computed as a function of temperature and pressure for the simple crystal of diamond and compared with accurate experimental data. Convergence of computed properties with respect to super-cell size is critically discussed. The effect on such properties of the adopted exchange-correlation functional of the density-functional-theory is discussed by considering three different levels of approximation (including hybrids): it is found to be rather small for the temperature dependence of equilibrium volume and bulk modulus, whereas it is quite large as regards their absolute values. PMID:25273420
Steinmann, Casper; Fedorov, Dmitri G.; Jensen, Jan H.
2013-01-01
We extend the Effective Fragment Molecular Orbital (EFMO) method to the frozen domain approach where only the geometry of an active part is optimized, while the many-body polarization effects are considered for the whole system. The new approach efficiently mapped out the entire reaction path of chorismate mutase in less than four days using 80 cores on 20 nodes, where the whole system containing 2398 atoms is treated in the ab initio fashion without using any force fields. The reaction path is constructed automatically with the only assumption of defining the reaction coordinate a priori. We determine the reaction barrier of chorismate mutase to be kcal mol−1 for MP2/cc-pVDZ and for MP2/cc-pVTZ in an ONIOM approach using EFMO-RHF/6-31G(d) for the high and low layers, respectively. PMID:23593259
Enhanced Magnetoabsorption Oscillations in Semiconductor Nanorings
NASA Astrophysics Data System (ADS)
Citrin, David; Maslov, Alex
2003-03-01
We present calculations of the interband optical absorption of semiconductor nanoscale rings including essential excitonic effects. We show that an in-plane electric field can significantly enhance the depth of magnetoabsorption oscillations due to Aharonov-Bohm like effects in the optical properties.
Ab initio determination of effective electron-phonon coupling factor in copper
NASA Astrophysics Data System (ADS)
Ji, Pengfei; Zhang, Yuwen
2016-04-01
The electron temperature Te dependent electron density of states g (ε), Fermi-Dirac distribution f (ε), and electron-phonon spectral function α2 F (Ω) are computed as prerequisites before achieving effective electron-phonon coupling factor Ge-ph. The obtained Ge-ph is implemented into a molecular dynamics (MD) and two-temperature model (TTM) coupled simulation of femtosecond laser heating. By monitoring temperature evolutions of electron and lattice subsystems, the result utilizing Ge-ph from ab initio calculation shows a faster decrease of Te and increase of Tl than those using Ge-ph from phenomenological treatment. The approach of calculating Ge-ph and its implementation into MD-TTM simulation is applicable to other metals.
Schroyen, M; Goddeeris, B M; Stinckens, A; Verhelst, R; Janssens, S; Cox, E; Georges, M; Niewold, T; Buys, N
2013-03-15
Diarrhoea in neonatal and early-weaned piglets due to enterotoxigenic Escherichia coli-F4 (ETEC-F4) is an important problem in the pig farming industry. There is substantial evidence for a genetic basis for susceptibility to ETEC-F4 since not all pigs suffer from diarrhoea after an ETEC-F4 infection. A region on SSC13 has been found to be in close linkage to the susceptibility of piglets for ETEC-F4ab,ac. Potential candidate genes on SSC13 have been examined and although some polymorphisms were found to be in linkage disequilibrium with the phenotype, the causative mutation has not yet been found. In this study we are looking at the expression of porcine genes in relation to ETEC-F4ab,ac. With the aid of the Affymetrix GeneChip Porcine Genome Array we were able to find differentially expressed genes between ETEC-F4ab,ac receptor positive (Fab,acR(+)) piglets without diarrhoea and F4ab,acR(+) piglets with diarrhoea or F4ab,acR(-) animals. Since the susceptibility to ETEC-F4ab,ac was described as a Mendelian trait, it is not so surprisingly that only two differentially expressed genes, transferrin receptor (TFRC) and trefoil factor 1 (TFF1), came out of the analysis. Although both genes could pass for functional candidate genes only TFRC also mapped to the region on SSC13 associated with susceptibility for ETEC-F4, which makes TFRC a positional functional candidate gene. Validation by qRT-PCR confirmed the differential expression of TFRC and TFF1. In piglets without diarrhoea, the expression of both genes was higher in F4ab,acR(+) than in F4ab,acR(-) piglets. Similarly, TFRC and TFF1 expression in F4ab,acR(+) piglets without diarrhoea was also higher than in F4ab,acR(+) piglets with diarrhoea. Consequently, although both genes might not play a role as receptor for F4 fimbriae, they could be of great importance during an ETEC-F4 outbreak. An upregulation of TFRC can be a consequence of the piglets ability to raise an effective immune response. An elevation of TFF1, a
How to Test Atom and Neutron Neutrality with Atom Interferometry
Arvanitaki, Asimina; Dimopoulos, Savas; Geraci, Andrew A.; Hogan, Jason; Kasevich, Mark
2008-03-28
We propose an atom-interferometry experiment based on the scalar Aharonov-Bohm effect which detects an atom charge at the 10{sup -28}e level, and improves the current laboratory limits by 8 orders of magnitude. This setup independently probes neutron charges down to 10{sup -28}e, 7 orders of magnitude below current bounds.
How to test atom and neutron neutrality with atom interferometry.
Arvanitaki, Asimina; Dimopoulos, Savas; Geraci, Andrew A; Hogan, Jason; Kasevich, Mark
2008-03-28
We propose an atom-interferometry experiment based on the scalar Aharonov-Bohm effect which detects an atom charge at the 10{-28}e level, and improves the current laboratory limits by 8 orders of magnitude. This setup independently probes neutron charges down to 10{-28}e, 7 orders of magnitude below current bounds. PMID:18517846
Suppression of decoherence in a graphene monolayer ring
Smirnov, D. Rode, J. C.; Haug, R. J.
2014-08-25
The influence of high magnetic fields on coherent transport is investigated. A monolayer graphene quantum ring is fabricated and the Aharonov-Bohm effect is observed. For increased magnitude of the magnetic field, higher harmonics appear. This phenomenon is attributed to an increase of the phase coherence length due to reduction of spin flip scattering.
Nontrivial systems and the necessity of the scalar quantum mechanics axioms
NASA Astrophysics Data System (ADS)
KotÅ¯lek, Jan
2009-06-01
We discuss the necessity of the axioms of scalar quantum mechanics introduced by Paschke and clearly demonstrate their geometric and/or physical meaning. We show that reasonable nonrelativistic quantum mechanics is exactly specified by the axioms. A system describing the electric Aharonov-Bohm effect is presented. It illustrates the topological obstructions for the existence of a Hamiltonian.
Testing Atom and Neutron Neutrality with Atom Interferometry
Arvanitaki, Asimina; Dimopoulos, Savas; Geraci, Andrew A.; Hogan, Jason; Kasevich, Mark; /Stanford U., Phys. Dept.
2008-01-07
We propose an atom-interferometry experiment based on the scalar Aharonov-Bohm effect which detects an atom charge at the 10{sup -28} e level, and improves the current laboratory limits by 8 orders of magnitude. This setup independently probes neutron charges down to 10{sup 28} e, 7 orders of magnitude below current bounds.
NASA Astrophysics Data System (ADS)
Ikeda, Takashi; Hirata, Masaru; Kimura, Takaumi
2003-12-01
The solvation shell structure and dynamics of Al3+ and Cl- in an aqueous solution of 0.8 M AlCl3 are studied under ambient conditions by using an ab initio molecular dynamics method. The solvation structures obtained from our ab initio simulations are in good agreement with the experimental ones for both Al3+ and Cl-. A detailed analysis of intramolecular geometry of hydration waters and dipole moments of the ingredients shows that the polarization has substantial effects on the structures and dynamics of both the cation and anion hydration shells. Implications for metal hydrolysis of Al3+ will also be given.
Ab initio study of the effect of vacancies on the thermal conductivity of boron arsenide
NASA Astrophysics Data System (ADS)
Protik, Nakib Haider; Carrete, Jesús; Katcho, Nebil A.; Mingo, Natalio; Broido, David
2016-07-01
Using a first principles theoretical approach, we show that vacancies give anomalously strong suppression of the lattice thermal conductivity κ of cubic Boron arsenide (BAs), which has recently been predicted to have an exceptionally high κ . This effect is tied to the unusually large phonon lifetimes in BAs and results in a stronger reduction in the BAs κ than occurs in diamond. The large changes in bonding around vacancies cannot be accurately captured using standard perturbative methods and are instead treated here using an ab initio Green function approach. As and B vacancies are found to have similar effects on κ . In contrast, we show that commonly used mass disorder models for vacancies fail for large mass ratio compounds such as BAs, incorrectly predicting much stronger (weaker) phonon scattering when the vacancy is on the heavy (light) atom site. The quantitative treatment given here contributes to fundamental understanding of the effect of point defects on thermal transport in solids and provides guidance to synthesis efforts to grow high quality BAs.
Ab initio approach to effective single-particle energies in doubly closed shell nuclei
NASA Astrophysics Data System (ADS)
Duguet, T.; Hagen, G.
2012-03-01
The present work discusses, from an ab initio standpoint, the definition, the meaning, and the usefulness of effective single-particle energies (ESPEs) in doubly closed shell nuclei. We perform coupled-cluster calculations to quantify to what extent selected closed-shell nuclei in the oxygen and calcium isotopic chains can effectively be mapped onto an effective independent-particle picture. To do so, we revisit in detail the notion of ESPEs in the context of strongly correlated many-nucleon systems and illustrate the necessity of extracting ESPEs through the diagonalization of the centroid matrix, as originally argued by Baranger. For the purpose of illustration, we analyze the impact of correlations on observable one-nucleon separation energies and nonobservable ESPEs in selected closed-shell oxygen and calcium isotopes. We then state and illustrate the nonobservability of ESPEs. Similarly to spectroscopic factors, ESPEs can indeed be modified by a redefinition of inaccessible quantities while leaving actual observables unchanged. This leads to the absolute necessity of employing consistent structure and reaction models based on the same nuclear Hamiltonian to extract the shell structure in a meaningful fashion from experimental data.
Sum, A.K.; Sandler, S.I.
2000-02-17
The results of ab initio calculations for cyclic clusters of methanol, ethanol, 1-propanol, and methanethiol are presented. Dimer, trimer, and tetramer clusters of all four compounds are studied, as are pentamer and hexamer clusters of methanol. From optimized clusters at HG/6--31G**, total energies and binding energies were calculated with both the HF and MP2 theories using the aug-cc-pVDZ basis set. Accurate binding energies were also calculated for the dimer and trimer of methanol using symmetry-adapted perturbation theory with the same basis set. Intermolecular and intramolecular distances, charge distribution of binding sites, binding energies, and equilibrium constants were computed to determine the hydrogen bond cooperativity effect for each species. The cooperativity effect, exclusive to hydrogen bonding systems, results form specific forces among the molecules, in particular charge-transfer processes and the greater importance of interactions between molecules not directly hydrogen bonded because of the longer range of the interactions. The ratios of equilibrium constants for forming multimer hydrogen bonds to that for dimer hydrogen bond formation increase rapidly with the cluster size, in contrast to the constant value commonly used in thermodynamic models for hydrogen bonding liquids.
Optical properties of surfaces with supercell ab initio calculations: Local-field effects
NASA Astrophysics Data System (ADS)
Tancogne-Dejean, Nicolas; Giorgetti, Christine; Véniard, Valérie
2015-12-01
Surface optical and electronic properties are crucial for material science and have implications in fields as various as nanotechnology, nonlinear optics, and spectroscopies. In particular, the huge variation of electronic density perpendicular to the surface is expected to play a key role in absorption due to local-field effects. Numerous state-of-the-art theoretical and numerical ab initio formalisms developed for studying these properties are based on supercell approaches, in reciprocal space, due to their efficiency. In this paper, we show that the standard scheme fails for the out-of-plane optical response of the surface. This response is interpreted using the "effective-medium theory" with vacuum and also in terms of interaction between replicas, as the supercell approach implies a periodicity which is absent in the real system. We propose an alternative formulation, also based on the supercell, for computing the macroscopic dielectric function. Application to the clean Si(001) 2 ×1 surface allows us to present the effect of the local fields for both peak positions and line shape on the bulk and surface contributions. It shows how local fields built up for the in-plane and out-of-plane dielectric responses of the surface. In addition to their conceptual impact, our results explain why the standard approach gives reliable predictions for the in-plane components, leading to correct reflectance anisotropy spectra. Our scheme can be further generalized to other low-dimensional geometries, such as clusters or nanowires, and open the way to nonlinear optics for surfaces.
Marsalek, Ondrej; Markland, Thomas E
2016-02-01
Path integral molecular dynamics simulations, combined with an ab initio evaluation of interactions using electronic structure theory, incorporate the quantum mechanical nature of both the electrons and nuclei, which are essential to accurately describe systems containing light nuclei. However, path integral simulations have traditionally required a computational cost around two orders of magnitude greater than treating the nuclei classically, making them prohibitively costly for most applications. Here we show that the cost of path integral simulations can be dramatically reduced by extending our ring polymer contraction approach to ab initio molecular dynamics simulations. By using density functional tight binding as a reference system, we show that our ring polymer contraction scheme gives rapid and systematic convergence to the full path integral density functional theory result. We demonstrate the efficiency of this approach in ab initio simulations of liquid water and the reactive protonated and deprotonated water dimer systems. We find that the vast majority of the nuclear quantum effects are accurately captured using contraction to just the ring polymer centroid, which requires the same number of density functional theory calculations as a classical simulation. Combined with a multiple time step scheme using the same reference system, which allows the time step to be increased, this approach is as fast as a typical classical ab initio molecular dynamics simulation and 35× faster than a full path integral calculation, while still exactly including the quantum sampling of nuclei. This development thus offers a route to routinely include nuclear quantum effects in ab initio molecular dynamics simulations at negligible computational cost. PMID:26851913
Metformin Enhances the Therapy Effects of Anti-IGF-1R mAb Figitumumab to NSCLC.
Cao, Hongxin; Dong, Wei; Qu, Xiao; Shen, Hongchang; Xu, Jun; Zhu, Linhai; Liu, Qi; Du, Jiajun
2016-01-01
The insulin-like growth factor (IGF) signaling system plays a critical role in tumorigenesis, highlighting the potential of targeting IGF-1R as an anti-cancer therapy. Although multiple anti-IGF-1R monoclonal antibody (mAb) drugs have been developed, challenges remain in the validation of the therapeutic effects and understanding the molecular mechanism of these mAbs. Herein, we conducted a study to validate the effect of Figitumumab (CP), an anti-IGF-1R mAb, in a panel of non-small cell lung cancer (NSCLC) cell lines. We found all tested cell lines were sensitive to CP, and CP could block IGF-1R and the downstream PI3K/AKT pathway activation. Unexpectedly, we found CP could activate ERK signaling pathway in IGF-1R kinase independent manner, which we further verified was mainly mediated by β-arrestin2. We also investigated the anti-tumor effect of metformin alone as well as its combination with CP to target NSCLC. Metformin could target IGF-1R signaling pathway by attenuating PI3K/AKT and MEK/ERK signaling pathways and down-regulating IGF-1R. Finally, we found that combining metformin with CP could further induce IGF-1R down-regulation and was more effective to target NSCLC cells. Our data suggests the combining of metformin with CP has additive therapeutic value against NSCLC. PMID:27488947
Metformin Enhances the Therapy Effects of Anti-IGF-1R mAb Figitumumab to NSCLC
Cao, Hongxin; Dong, Wei; Qu, Xiao; Shen, Hongchang; Xu, Jun; Zhu, Linhai; Liu, Qi; Du, Jiajun
2016-01-01
The insulin-like growth factor (IGF) signaling system plays a critical role in tumorigenesis, highlighting the potential of targeting IGF-1R as an anti-cancer therapy. Although multiple anti-IGF-1R monoclonal antibody (mAb) drugs have been developed, challenges remain in the validation of the therapeutic effects and understanding the molecular mechanism of these mAbs. Herein, we conducted a study to validate the effect of Figitumumab (CP), an anti-IGF-1R mAb, in a panel of non-small cell lung cancer (NSCLC) cell lines. We found all tested cell lines were sensitive to CP, and CP could block IGF-1R and the downstream PI3K/AKT pathway activation. Unexpectedly, we found CP could activate ERK signaling pathway in IGF-1R kinase independent manner, which we further verified was mainly mediated by β-arrestin2. We also investigated the anti-tumor effect of metformin alone as well as its combination with CP to target NSCLC. Metformin could target IGF-1R signaling pathway by attenuating PI3K/AKT and MEK/ERK signaling pathways and down-regulating IGF-1R. Finally, we found that combining metformin with CP could further induce IGF-1R down-regulation and was more effective to target NSCLC cells. Our data suggests the combining of metformin with CP has additive therapeutic value against NSCLC. PMID:27488947
Bogle, A C; Reed, T; Norton, J A
1994-01-01
Asymmetry of a-b ridge count, a dermatoglyphic trait in the second interdigital (ID II) palmar area was studied in 314 identical (MZ) twin-pairs of known placental type. Statistically significant differences were observed for the variability of a-b ridge count with respect to placentation. Monochorionic MZ pairs displayed more within-pair variability than dichorionic MZ twins. Within dichorionic pairs, greater variability was observed in MZ twins when pairs with fused placentas were compared with those with separate placentas. A similar pattern of greater variability in dichorionic fused versus dichorionic separate placentas was also found in 121 same sex dizygotic twin-pairs. The pattern of within-pair differences was consistent with a placental proximity effect like that known for the variability in birth weight in twins. PMID:8039800
Dane Morgan
2010-06-10
The project began March 13, 2006, allocated for three years, and received a one year extension from March 13, 2009 to March 12, 2010. It has now completed 48 of 48 total months. The project was focused on using ab initio methods to gain insights into radiation induced segregation (RIS) in Ni-Fe-Cr alloys. The project had the following key accomplishments • Development of a large database of ab initio energetics that can be used by many researchers in the future for increased understanding of this system. For example, we have the first calculations showing a dramatic stabilization effect of Cr-Cr interstitial dumbbells in Ni. • Prediction of both vacancy and interstitial diffusion constants for Ni-Cr and Ni-Fe for dilute Cr and Fe. This work included generalization of widely used multifrequency models to make use of ab initio derived energetics and thermodynamics. • Prediction of qualitative trends of RIS from vacancy and interstitial mechanisms, suggesting the two types of defect fluxes drive Cr RIS in opposite directions. • Detailed kinetic Monte Carlo modeling of diffusion by vacancy mechanism in Ni-Cr as a function of Cr concentration. The results demonstrate that Cr content can have a significant effect on RIS. • Development of a quantitative RIS transport model, including models for thermodynamic factors and boundary conditions.
Postural Change Effects on Infants' AB Task Performance: Visual, Postural, or Spatial?
ERIC Educational Resources Information Center
Lew, Adina R.; Hopkins, Brian; Owen, Laura H.; Green, Michael
2007-01-01
Smith and colleagues (Smith, L. B., Thelen, E., Titzer, R., & McLin, D. (1999). Knowing in the context of acting: The task dynamics of the A-not-B error. "Psychological Review, 106," 235-260) demonstrated that 10-month-olds succeed on a Piagetian AB search task if they are moved from a sitting position to a standing position between A and B…
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.
Liang, Hung-Hua; Wei, Po-Li; Hung, Chin-Sheng; Wu, Chun-Te; Wang, Weu; Huang, Ming-Te; Chang, Yu-Jia
2013-10-01
MicroRNAs (miRNAs) play an essential role in regulating gene expression in normal and malignant cells. Expression of the microRNA-200 (miR-200) family has been correlated with malignancy in cancers. However, whether miR-200a/b plays a role in curcumin-mediated treatment of hepatocellular carcinoma (HCC) is unknown. We performed miRNA array analyses in two different HCC cell lines (HepG2 and HepJ5). The expression patterns of miR-200 family members were assessed with real-time PCR. We overexpressed miR-200 family members using a lentiviral system and selected stably transduced clones with antibiotics. The anticancer effects of curcumin on J5-200a, J5-200b, and J5-control cells were assessed by MTT assay, flow cytometry cell cycle analysis, and TUNEL assay. We found that HepG2 cells, which were more resistant to curcumin treatment than HepJ5 cells, expressed higher levels of miR-200a/b. The MTT assay revealed that the overexpression of miR-200a/b in HepJ5 cells conferred enhanced resistance to curcumin treatment compared with the control cells. By cell cycle analysis and TUNEL assay, we found that apoptosis was increased dramatically in J5-control cells compared with J5-200a and J5-200b cells after curcumin treatment. Finally, we evaluated the levels of Bcl-2, Bax, and Bad, and found a decrease of Bcl-2 levels and increase of Bad levels in the J5-control cells treated with curcumin. The expression levels of miR-200a/b might determine the therapeutic efficacy of curcumin on HCC cells. PMID:23760980
Lesinski, T.; Meyer, J.
2006-10-15
We study the effect of the splitting of neutron and proton effective masses with isospin asymmetry on the properties of the Skyrme energy density functional. We discuss the ability of the latter to predict observables of infinite matter and finite nuclei, paying particular attention to controlling the agreement with ab initio predictions of the spin-isospin content of the nuclear equation of state, as well as diagnosing the onset of finite size instabilities, which we find to be of critical importance. We show that these various constraints cannot be simultaneously fulfilled by the standard Skyrme force, calling at least for an extension of its P-wave part.
Schuman, Joel S.; Brown, Eric N.
2016-01-01
Purpose To compare intraocular pressure (IOP) reduction and to develop a predictive surgery calculator based on the results between trabectome-mediated ab interno trabeculectomy in pseudophakic patients versus phacoemulsification combined with trabectome-mediated ab interno trabeculectomy in phakic patients. Methods This observational surgical cohort study analyzed pseudophakic patients who received trabectome-mediated ab interno trabeculectomy (AIT) or phacoemulsification combined with AIT (phaco-AIT). Follow up for less than 12 months or neovascular glaucoma led to exclusion. Missing data was imputed by generating 5 similar but non-identical datasets. Groups were matched using Coarsened Exact Matching based on age, gender, type of glaucoma, race, preoperative number of glaucoma medications and baseline intraocular pressure (IOP). Linear regression was used to examine the outcome measures consisting of IOP and medications. Results Of 949 cases, 587 were included consisting of 235 AIT and 352 phaco-AIT. Baseline IOP between groups was statistically significant (p≤0.01) in linear regression models and was minimized after Coarsened Exact Matching. An increment of 1 mmHg in baseline IOP was associated with a 0.73±0.03 mmHg IOP reduction. Phaco-AIT had an IOP reduction that was only 0.73±0.32 mmHg greater than that of AIT. The resulting calculator to determine IOP reduction consisted of the formula -13.54+0.73 × (phacoemulsification yes:1, no:0) + 0.73 × (baseline IOP) + 0.59 × (secondary open angle glaucoma yes:1, no:0) + 0.03 × (age) + 0.09 × (medications). Conclusions This predictive calculator for minimally invasive glaucoma surgery can assist clinical decision making. Only a small additional IOP reduction was observed when phacoemulsification was added to AIT. Patients with a higher baseline IOP had a greater IOP reduction. PMID:27077914
Plotnikov, Nikolay; Kamerlin, Shina Caroline Lynn; Warshel, Arieh
2011-01-01
Recent years have seen tremendous effort in the development of approaches with which to obtain quantum mechanics/molecular mechanics (QM/MM) free energies for reactions in the condensed phase. Nevertheless, there remain significant challenges to address, particularly the high computational cost involved in performing proper configurational sampling and in particular in obtaining ab initio QM/MM (QM(ai)/MM) free energy surfaces. One increasingly popular approach that seems to offer an ideal way to progress in this direction is the elegant metadynamics (MTD) approach. However, in the current work we point out the subtle efficiency problems associated with this approach, and illustrate that we have at hand what is arguably a more powerful approach. More specifically, we demonstrate the effectiveness of an updated version of our original idea of using a classical reference potential for QM(ai)/MM calculations [J. Phys. Chem. B. 102 (1998), 2293)], which we refer to as “paradynamics” (PD). This approach is based on the use of an empirical valence bond (EVB) reference potential, which is already similar to the real ab initio potential. The reference potential is fitted to the ab initio potential by an iterative and, to a great degree, automated refinement procedure. The corresponding free energy profile is then constructed using the refined EVB potential, and the linear response approximation (LRA) is used to evaluate the QM(ai)/MM activation free energy barrier. The automated refinement of the EVB surface (and thus the reduction of the difference between the reference and ab initio potentials) is a key factor in accelerating the convergence of the LRA approach. We apply our PD approach to a test reaction, namely the SN2 reaction between chloride ion and methyl chloride, and demonstrate that, at present, this approach is far more powerful and cost effective than the metadynamics approach (at least in its current implementation). We also discuss the general features
van der Merwe, Frances; Bezuidenhout, Carlos; van den Berg, Johnnie; Maboeta, Mark
2012-01-01
A 28-day study was conducted to determine the effects of the Bacillus thuringiensis Cry1Ab toxin on the earthworm Eisenia andrei. Previously, investigations have been limited to life-cycle level effects of this protein on earthworms, and mostly on E. fetida. In this study several endpoints were compared which included biomass changes, cocoon production, hatching success, a cellular metal-stress biomarker (Neutral Red Retention Time; NRRT) and potential genotoxic effects in terms of Randomly Amplified Polymorphic DNA sequences (RAPDs). NRRT results indicated no differences between treatments (p > 0.36), and NRRT remained the same for both treatments at different times during the experiment (p = 0.18). Likewise, no significant differences were found for cocoon production (p = 0.32) or hatching success (p = 0.29). Conversely, biomass data indicated a significant difference between the control treatment and the Bt treatment from the second week onwards (p < 0.001), with the Bt treatment losing significantly more weight than the isoline treatment. Possible confounding factors were identified that might have affected the differences in weight loss between groups. From the RAPD profiles no conclusive data were obtained that could link observed genetic variation to exposure of E. andrei to Cry1Ab proteins produced by Bt maize. PMID:23235452
van der Merwe, Frances; Bezuidenhout, Carlos; van den Berg, Johnnie; Maboeta, Mark
2012-01-01
A 28-day study was conducted to determine the effects of the Bacillus thuringiensis Cry1Ab toxin on the earthworm Eisenia andrei. Previously, investigations have been limited to life-cycle level effects of this protein on earthworms, and mostly on E. fetida. In this study several endpoints were compared which included biomass changes, cocoon production, hatching success, a cellular metal-stress biomarker (Neutral Red Retention Time; NRRT) and potential genotoxic effects in terms of Randomly Amplified Polymorphic DNA sequences (RAPDs). NRRT results indicated no differences between treatments (p > 0.36), and NRRT remained the same for both treatments at different times during the experiment (p = 0.18). Likewise, no significant differences were found for cocoon production (p = 0.32) or hatching success (p = 0.29). Conversely, biomass data indicated a significant difference between the control treatment and the Bt treatment from the second week onwards (p < 0.001), with the Bt treatment losing significantly more weight than the isoline treatment. Possible confounding factors were identified that might have affected the differences in weight loss between groups. From the RAPD profiles no conclusive data were obtained that could link observed genetic variation to exposure of E. andrei to Cry1Ab proteins produced by Bt maize. PMID:23235452
Bondzio, Angelika; Lodemann, Ulrike; Weise, Christoph; Einspanier, Ralf
2013-01-01
In vitro testing can contribute to reduce the risk that the use of genetically modified (GM) crops and their proteins show unintended toxic effects. Here we introduce a porcine intestinal cell culture (IPEC-J2) as appropriate in vitro model and tested the possible toxic potential of Cry1Ab protein, commonly expressed in GM-maize. For comprehensive risk assessment we used WST-1 conversion and ATP content as metabolic markers for proliferation, lactate dehydrogenase release as indicator for cells with compromised membrane and transepithelial electrical resistance as parameter indicating membrane barrier function. The results were compared to the effects of valinomycin, a potassium ionophore, known to induce cytotoxic effects in most mammalian cell types. Whereas no toxicity was observed after Cry1Ab treatment, valinomycin induced a decrease in IPEC-J2 viability. This was confirmed by dynamic monitoring of cellular responses. Additionally, two dimensional differential in-gel electrophoresis was performed. Only three proteins were differentially expressed. The functions of these proteins were associated with responses to stress. The up-regulation of heat shock protein Hsp70 was verified by Western blotting as well as by enzyme-linked immunosorbent assay and may be related to a protective function. These findings suggest that the combination of in vitro testing and proteomic analysis may serve as a promising tool for mechanism based safety assessment. PMID:23861753
Wikfeldt, K. T.; Michaelides, A.
2014-01-28
Ab initio simulations that account for nuclear quantum effects have been used to examine the order-disorder transition in squaric acid, a prototypical H-bonded antiferroelectric crystal. Our simulations reproduce the >100 K difference in transition temperature observed upon deuteration as well as the strong geometrical isotope effect observed on intermolecular separations within the crystal. We find that collective transfer of protons along the H-bonding chains – facilitated by quantum mechanical tunneling – is critical to the order-disorder transition and the geometrical isotope effect. This sheds light on the origin of isotope effects and the importance of tunneling in squaric acid which likely extends to other H-bonded ferroelectrics.
Fano effect in an AB interferometer with a quantum dot side-coupled to a single Majorana bound state
NASA Astrophysics Data System (ADS)
Zeng, Qi-Bo; Chen, Shu; Lü, Rong
2016-02-01
We study the conductance and interference effects through an AB interferometer with an embedded quantum dot (QD) side-coupled to a single Majorana bound state (MBS) by using non-equilibrium Green's function method. The energy levels appearing in the QD are calculated by diagonalizing the Hamiltonian of the embedded QD-MBS system. When the single QD energy level ɛ0 is set to 0, there are three discrete energy levels in the QD appearing at around ω = 0, ±√{ ɛM2 + 2λ2 } due to the coupling with MBS where ɛM is the coupling strength between the two MBSs at the two ends of the nanowire and λ is the coupling strength between the MBS and the QD. Asymmetric Fano lineshapes are found around these levels in the conductance due to the interference between electrons traversing through different paths. The phase shift of electrons through the QD changes from π / 2 to - π / 2 at each of these three energy values. However, the phase does not vary smoothly between these three energy levels but shows severe changes from - π / 2 to π / 2 at ω = ±√{ ɛM2 +λ2 }. As a comparison, we also study the similar AB interferometer in which the QD-MBS system is replaced by a normal QD-QD system or a simple single QD system, which shows only two or one Fano peak and the phase shifts from π / 2 to - π / 2 only at the Fano peaks. These differences reflect the distinct influences of Majorana bound state on the transport properties of AB interferometer.
Ab-initio study of pressure effects and hydrogen impurity in HgO
NASA Astrophysics Data System (ADS)
Choi, Minseok; Park, Chul-Hong
2016-06-01
Through ab-initio pseudopotential calculations, we investigated the deformation potential of HgO semiconductors and the structural stabilities of various crystal structures under pressure. We also investigated the microscopic structure of the hydrogen (H) impurity in HgO. Especially the state of hydrogen atoms captured by an acceptor-like Hg-vacancy (V Hg ) is focused on. The location of H is found to be very different from the original Hg-site, forming a strong H-O bond. The capture two H atoms by V Hg is found to be energetically favorable: the binding energy for one H and the second H are 1.01 eV and 0.07 eV, respectively.
Ab initio study of the effect of vacancies on the thermal conductivity
NASA Astrophysics Data System (ADS)
Protik, Nakib; Carrete, Jesus; Mingo, Natalio; Katcho, Nebil; Broido, David
Point defects and vacancies in particular can have a profound impact on phonon thermal transport. Examples are seen in diamond and cubic boron arsenide where large C and As vacancy concentrations give much lower thermal conductivity than expected. Here, we calculate the phonon-vacancy scattering rates using an ab initioGreen's function approach, which treats the scattering to all orders in contrast to standard perturbation theory approaches. The lattice thermal conductivity, k, is calculated from first principles by solving the Boltzmann transport equation for phonons, with interatomic force constants determined using density functional theory. The reduction in k with vacancy defect density is assessed. The phonon-vacancy scattering can show significant differences using the Green's function method compared to what would be predicted from the perturbative Born approximation, consistent with previous findings for diamond.
Mahmoud, A; Erba, A; Doll, K; Dovesi, R
2014-06-21
A general methodology has been devised and implemented into the solid-state ab initio quantum-mechanical Crystal program for studying the evolution under geophysical pressure of the elastic anisotropy of crystalline materials. This scheme, which fully exploits both translational and point symmetry of the crystal, is developed within the formal frame of one-electron Hamiltonians and atom-centered basis functions. Six silicate garnet end-members, among the most important rock-forming minerals of the Earth's mantle, are considered, whose elastic anisotropy is fully characterized under high hydrostatic compressions, up to 60 GPa. The pressure dependence of azimuthal anisotropy and shear-wave birefringence of seismic wave velocities for these minerals are accurately simulated and compared with available single-crystal measurements. PMID:24952556
Mahmoud, A.; Erba, A. Dovesi, R.; Doll, K.
2014-06-21
A general methodology has been devised and implemented into the solid-state ab initio quantum-mechanical CRYSTAL program for studying the evolution under geophysical pressure of the elastic anisotropy of crystalline materials. This scheme, which fully exploits both translational and point symmetry of the crystal, is developed within the formal frame of one-electron Hamiltonians and atom-centered basis functions. Six silicate garnet end-members, among the most important rock-forming minerals of the Earth's mantle, are considered, whose elastic anisotropy is fully characterized under high hydrostatic compressions, up to 60 GPa. The pressure dependence of azimuthal anisotropy and shear-wave birefringence of seismic wave velocities for these minerals are accurately simulated and compared with available single-crystal measurements.
Burns, Andrea; Raybould, Alan
2014-12-01
Event 5307 transgenic maize produces the novel insecticidal protein eCry3.1Ab, which is active against certain coleopteran pests such as Western corn rootworm (Diabrotica virgifera virgifera). Laboratory tests with representative nontarget organisms (NTOs) were conducted to test the hypothesis of no adverse ecological effects of cultivating Event 5307 maize. Estimates of environmental eCry3.1Ab concentrations for each NTO were calculated from the concentrations of eCry3.1Ab produced by 5307 maize in relevant plant tissues. Nontarget organisms were exposed to diets containing eCry3.1Ab or diets comprising Event 5307 maize tissue and evaluated for effects compared to control groups. No statistically significant differences in survival were observed between the control group and the group exposed to eCry3.1Ab in any organism tested. Measured eCry3.1Ab concentrations in the laboratory studies were equal to or greater than the most conservative estimates of environmental exposure. The laboratory studies corroborate the hypothesis of negligible ecological risk from the cultivation of 5307 maize. PMID:24407432
Yoon, Byung-Hak; Lee, Jae Hyup; Na, Kyuheum; Ahn, Chihoon; Cho, Jongho; Ahn, Hyun Chan; Choi, Jungyoun; Oh, Hyosun; Kim, Byong Moon; Choe, Senyon
2016-07-01
The purpose of this study was to determine the effects of a single intravenous injection of a novel osteoinductive material, activin A/BMP-2 (AB204), to rodents on toxicity and their respiratory functions and central nervous system (CNS). A single intravenous injection of AB204 was given to Sprague-Dawley (SD) rats in doses of 0, 0.625, 2.5 and 10 mg/kg to observe the mortality rate, the general symptoms for 14 days. The experimental groups were also given 0.2, 0.4 and 0.8 mg/kg of AB204, respectively, and the respiration rate, the tidal volume and the minute volume were measured for 240 min. The experimental groups of imprinting control region (ICR) mice were given a single intravenous injection of 0.2, 0.4 and 0.8 mg/kg of AB204, respectively. Their body temperature was taken and general behaviors were observed to evaluate the effect of AB204 on the CNS for 240 min. The study on toxicity of a single intravenous injection found no death or abnormal symptoms, abnormal findings from autopsy, or abnormal body weight gain or loss in all the experimental groups. No abnormal variation associated with the test substance was observed in the respiration rate, the tidal volume, the minute volume, body temperature or the general behaviors. On the basis of these results, the approximate lethal dose of AB204 for a single intravenous injection exceeds 10 mg/kg for SD rats and a single intravenous injection of ≤0.8 mg/kg AB204 has no effect on their respiratory system for SD rat and no effect on their CNS for ICR mice. PMID:26446865