Aharonov-Casher Effect Research Articles

Electric field effect on spin waves: Role of magnetic moment current

We show that a static electric field E x gives rise to a shift of the spin wave dispersion relation in the direction of the wave number q y of the quantity . This effect is caused by the magnetic moment current carried by the spin wave itself which generates an additional phase proportional to the electric field, as in the Aharonov-Casher effect. This effect is independent of the possibly present magneto-electric effects of insulating ferromagnets and superimposes to them.

Kondo effect in a Aharonov-Casher interferometer

We consider a model describing a spin field-effect transistor based on a quantum nanowire with a tunable spin-orbit interaction embedded between two ferromagnetic leads with anticollinear magnetization. We investigate a regime of a strong interplay between resonance Kondo scattering and interference associated with the Aharonov-Casher effect. Using the Keldysh technique at weak coupling regime we calculate perturbatively the charge current. It is predicted that the effects of the spin-orbit interaction result in a non-vanishing current for any spin polarization of the leads including the case of fully polarized anti-collinear contacts. We analyze the influence of the Aharonov-Casher phase and degree of spin polarization in the leads onto a Kondo temperature.

Universal quantum computing with parafermions assisted by a half-fluxon

Braiding of anyons such as Majoranas or parafermions provides only Clifford gates which do not form a universal set of quantum gates. We propose a robust and resource-efficient scheme to perform a non-Clifford gate on a logical qudit encoded in parafermionic zero modes via the Aharonov-Casher effect. This gate can be implemented by moving a half flux quantum around the pair of parafermionic zero modes. The parafermion modes can be realized in a two-dimensional set-up using existing proposals and a half fluxon carrying half flux quantum can be created as a part of a half fluxon/anti-half fluxon pair in a spin-triplet Josephson junction with a dipole defect. With an appropriate bias current pulse, the half fluxon can be braided around the parafermions. Supplementing this gate with the braiding of parafermions provides the avenue for universal quantum computing with parafermions without magic state distillation.

Energy Spectrum of a Dirac Particle with Position-Dependent Mass Under the Influence of the Aharonov-Casher Effect

In this paper, we investigate the influence of the Aharonov-Casher (AC) effect on the relativistic and nonrelativistic energy spectra of a neutral Dirac particle with position-dependent mass (PDM). To exactly solve our system, we use the projection operators left-handed and right-handed. Next, we explicitly determine the energy spectra for the bound states of the particle. As a result, we verify that the relativistic spectrum depends on the quantum numbers n and ml, AC quantum phase ΦAC generated by AC effect and of the parameter κ that characterize the PDM. In addition, this spectrum is a periodic function and increase in absolute values with the increase of ΦAC. We also verify that the energies of the particle are minors that of the antiparticle, and in the limit of the constant mass (κ → 0) the rest energy is recovered. However, in the absence of the AC effect (ΦAC → 0), the spectrum still remains quantized in terms of n and ml. Finally, we analyze the nonrelativistic limit of our work, where we obtain an energy spectrum with some characteristics similar to the relativistic case. Making an analogy with some works of the literature, in particular with the hydrogen atom, we note that our nonrelativistic spectrum provides the so-called binding energies, while that its absolute values provides the so-called ionization energies.

Microscopic origin of level attraction for a coupled magnon-photon system in a microwave cavity

We discuss various microscopic mechanisms for level attraction in a hybridized magnon-photon system of a ferromagnet in a microwave cavity. The discussion is based upon the electromagnetic theory of continuous media where the effects of the internal magnetization dynamics of the ferromagnet are described using dynamical response functions. This approach is in agreement with quantized multi-oscillator models of coupled photon-magnon dynamics. We demonstrate that to provide the attractive interaction between the modes, the effective response functions should be diamagnetic. Magneto-optical coupling is found to be one mechanism for the effective diamagnetic response, which is proportional to photon number. A dual mechanism based on the Aharonov–Casher effect is also highlighted, which is instead dependent on magnon number.

Topological, noninertial and spin effects on the 2D Dirac oscillator in the presence of the Aharonov\u2013Casher effect

In the present paper, we investigate the influence of topological, noninertial and spin effects on the 2D Dirac oscillator in the presence of the Aharonov–Casher effect. Next, we determine the two-component Dirac spinor and the relativistic energy spectrum for the bound states. We observe that this spinor is written in terms of the confluent hypergeometric functions and this spectrum explicitly depends on the quantum numbers n and m_l, parameters s and eta associated to the topological and spin effects, quantum phase varPhi _{AC}, and of the angular velocity varOmega associated to the noninertial effects of a rotating frame. In the nonrelativistic limit, we obtain the quantum harmonic oscillator with two types of couplings: the spin-orbit coupling and the spin-rotation coupling. We note that the relativistic and nonrelativistic spectra grow in absolute values as functions of eta , varOmega , and varPhi _{AC} and its periodicities are broken due to the rotating frame. Finally, we compared our problem with other works, where we verified that our results generalizes some particular planar cases of the literature.

Laser control of magnonic topological phases in antiferromagnets

We study the laser control of magnon topological phases induced by the Aharonov-Casher effect in insulating antiferromagnets (AFs). Since the laser electric field can be considered as a time-periodic perturbation, we apply the Floquet theory and perform the inverse frequency expansion by focusing on the high frequency region. Using the obtained effective Floquet Hamiltonian, we study nonequilibrium magnon dynamics away from the adiabatic limit and its effect on topological phenomena. We show that a linearly polarized laser can generate helical edge magnon states and induce the magnonic spin Nernst effect, whereas a circularly polarized laser can generate chiral edge magnon states and induce the magnonic thermal Hall effect. In particular, in the latter, we find that the direction of the magnon chiral edge modes and the resulting thermal Hall effect can be controlled by the chirality of the circularly polarized laser through the change from the left-circular to the right-circular polarization. Our results thus provide a handle to control and design magnon topological properties in the insulating AF.

Solution of the Dipoles in Noncommutative Space with Minimal Length**Supported by the National Natural Science Foundation of China under Grant Nos. 11465006 and 11565009

The single neutral spin-half particle with electric dipole moment and magnetic dipole moment moving in an external electromagnetic field is studied. The Aharonov-Casher effect and He-McKellar-Wilkens effect are emphatically discussed in noncommutative (NC) space with minimal length. The energy eigenvalues of the systems are obtained exactly in terms of the Jacobi polynomials. Additionally, a special case is discussed and the related energy spectra are plotted.

The Quaternionic Commutator Bracket and Its Implications

A quaternionic commutator bracket for position and momentum shows that the quaternionic wave function, viz. ψ ˜ = ( i c ψ 0 , ψ → ) , represents a state of a particle with orbital angular momentum, L = 3 ℏ , resulting from the internal structure of the particle. This angular momentum can be attributed to spin of the particle. The vector ψ → , points in an opposite direction of L → . When a charged particle is placed in an electromagnetic field, the interaction energy reveals that the magnetic moments interact with the electric and magnetic fields giving rise to terms similar to Aharonov–Bohm and Aharonov–Casher effects.

Charge quantum interference device

The demonstration of coherent quantum phase slips (CQPS) in disordered superconductors has opened up a new route towards exploring the fundamental charge–phase duality in superconductors, with the promise of devices with new functionalities and a robust quantum current standard based on CQPS. Here we demonstrate a device that integrates several CQPS junctions: the charge quantum interference device. The charge quantum interference device becomes the dual of the well-known superconducting quantum interference device, and is a manifestation of the Aharonov–Casher effect in a continuous superconducting system devoid of dielectric barriers.

Photoinduced Topological Phase Transitions in Topological Magnon Insulators

Topological magnon insulators are the bosonic analogs of electronic topological insulators. They are manifested in magnetic materials with topologically nontrivial magnon bands as realized experimentally in a quasi-two-dimensional (quasi-2D) kagomé ferromagnet Cu(1–3, bdc), and they also possess protected magnon edge modes. These topological magnetic materials can transport heat as well as spin currents, hence they can be useful for spintronic applications. Moreover, as magnons are charge-neutral spin-1 bosonic quasiparticles with a magnetic dipole moment, topological magnon materials can also interact with electromagnetic fields through the Aharonov-Casher effect. In this report, we study photoinduced topological phase transitions in intrinsic topological magnon insulators in the kagomé ferromagnets. Using magnonic Floquet-Bloch theory, we show that by varying the light intensity, periodically driven intrinsic topological magnetic materials can be manipulated into different topological phases with different sign of the Berry curvatures and the thermal Hall conductivity. We further show that, under certain conditions, periodically driven gapped topological magnon insulators can also be tuned to synthetic gapless topological magnon semimetals with Dirac-Weyl magnon cones. We envision that this work will pave the way for interesting new potential practical applications in topological magnetic materials.

Magnonic topological insulators in antiferromagnets

Extending the notion of symmetry protected topological phases to insulating antiferromagnets (AFs) described in terms of opposite magnetic dipole moments associated with the magnetic $\mathrm{N}\stackrel{\ifmmode \acute{}\else \'{}\fi{}}{\mathrm{e}}\mathrm{el}$ order, we establish a bosonic counterpart of topological insulators in semiconductors. Making use of the Aharonov-Casher effect, induced by electric field gradients, we propose a magnonic analog of the quantum spin Hall effect (magnonic QSHE) for edge states that carry helical magnons. We show that such up and down magnons form the same Landau levels and perform cyclotron motion with the same frequency but propagate in opposite direction. The insulating AF becomes characterized by a topological ${\mathbb{Z}}_{2}$ number consisting of the Chern integer associated with each helical magnon edge state. Focusing on the topological Hall phase for magnons, we study bulk magnon effects such as magnonic spin, thermal, Nernst, and Ettinghausen effects, as well as the thermomagnetic properties of helical magnon transport both in topologically trivial and nontrivial bulk AFs and establish the magnonic Wiedemann-Franz law. We show that our predictions are within experimental reach with current device and measurement techniques.

Aharonov-Casher effect and quantum transport in graphene based nano rings: A self-consistent Born approximation

In this study, Rashba coupling induced Aharonov-Casher effect in a graphene based nano ring is investigated theoretically. The graphene based nano ring is considered as a central device connected to semi-infinite graphene nano ribbons. In the presence of the Rashba spin-orbit interaction, two armchair shaped edge nano ribbons are considered as semi-infinite leads. The non-equilibrium Green’s function approach is utilized to obtain the quantum transport characteristics of the system. The relaxation and dephasing mechanisms within the self-consistent Born approximation is scrutinized. The Lopez-Sancho method is also applied to obtain the self-energy of the leads. We unveil that the non-equilibrium current of the system possesses measurable Aharonov-Casher oscillations with respect to the Rashba coupling strength. In addition, we have observed the same oscillations in dilute impurity regimes in which amplitude of the oscillations is shown to be suppressed as a result of the relaxations.

Chiral anomaly of Weyl magnons in stacked honeycomb ferromagnets

Chiral anomaly of Weyl magnons (WMs), featured by nontrivial band crossings at paired Weyl nodes (WNs) of opposite chirality, is investigated. It is shown that WMs can be realized in stacked honeycomb ferromagnets. Using the Aharonov-Casher effect that is about the interaction between magnetic moments and electric fields, the magnon motion in honeycomb layers can be quantized into magnonic Landau levels (MLLs). The zeroth MLL is chiral so that unidirectional WMs propagate in the perpendicular (to the layer) direction for a given WN under a magnetic field gradient from one WN to the other and change their chiralities, resulting in the magnonic chiral anomaly (MCA). A net magnon current carrying spin and heat through the zeroth MLL depends linearly on the magnetic field gradient and the electric field gradient in the ballistic transport.

Spin-dependent transport in multi-terminal Aharonov-Casher ring with quantum dot

The Aharonov-Casher (AC) effect is theoretically examined in a mesoscopic ring with an embedded quantum dot in a multi-terminal geometry. We examine a realistic model for such a system with spin-orbit interaction in the ring. A spin-polarized current can be generated in a three-terminal device even in the absence of magnetic field, whereas it cannot in a two-terminal device. The spin polarization is enhanced by the resonant tunneling around the Coulomb peak and Kondo effect in the Coulomb blockade regime. The efficiency for the spin polarization is discussed in realistic devices.

An Extended Dynamical Equation of Motion, Phase Dependency and Inertial Backreaction

Newton's second law has limited scope of application when transient phenomena are present. We consider a modification of Newton's second law in order to take into account a sudden change (surge) of angular momentum or linear momentum. We hypothesize that space itself resists such surges according to a kind of induction law (related to inertia); additionally, we provide further evidence of the "fluidic" nature of space itself. This "back-reaction" is quantified by the tendency of angular momentum flux threading across a surface. This quantity is mass-dependent, and bears similarity to the quantum mechanics phase shift, present in the Aharonov-Bohm and Aharonov-Casher effects. Furthermore, this provides evidence of vacuum polarization, a phenomena which is relative to local space indicating that local geometry and topology should be taken into account in any fundamental physical theory.

Magnonic quantum Hall effect and Wiedemann-Franz law

We present a quantum Hall effect of magnons in two-dimensional clean insulating magnets at finite temperature. Through the Aharonov-Casher effect, a magnon moving in an electric field acquires a geometric phase and forms Landau levels in an electric field gradient of sawtooth form. At low temperatures, the lowest energy band being almost flat carries a Chern number associated with a Berry curvature. Appropriately defining the thermal conductance for bosons, we find that the magnon Hall conductances get quantized and show a universal thermomagnetic behavior, i.e., are independent of materials, and obey a Wiedemann-Franz law for magnon transport. We consider magnons with quadratic and linear (Dirac-like) dispersions. Finally, we show that our predictions are within experimental reach for ferromagnets and skyrmion lattices with current device and measurement techniques.

Anomalous Oscillations due to Aharonov–Bohm and Aharonov–Casher Effects of the One-Dimensional Hubbard Ring in the Strong Coupling Limit

We investigate anomalous oscillations due to the Aharonov–Bohm (AB) and Aharonov–Casher (AC) effects of the one-dimensional Hubbard ring with flux in the strong coupling limit. By using the exact diagonalization method and the Shiba transformation, we examine the energies of the ground-state and a few excited states in the presence of the flux producing the AB or AC effect, where the transformation not only reverses the sign of the interaction U but also exchanges the role between the AB and AC effects in the model Hamiltonian. We systematically classify the AB and AC oscillations by using the number of minima Nmin of the ground-state energy as a function of a normalized phase shift ϕ for 0 ≤ ϕ < 1, and clarify the close relationship between the AB and AC effects. For example, it is shown that Nmin is given by NL − Ne (NL − N↑ + N↓) for the AB (AC) effect in the very strong attraction, where NL, Ne, N↑, and N↓ are the system size, the total number of electrons, the number of electrons with up-spin, and th...

Relativistic Anandan quantum phase and the Aharonov–Casher effect under Lorentz symmetry breaking effects in the cosmic string spacetime

From the modified Maxwell theory coupled to gravity, we establish a possible scenario of the violation of the Lorentz symmetry and write an effective metric for the cosmic string spacetime. Then, we investigate the arising of an analogue of the Anandan quantum phase for a relativistic Dirac neutral particle with a permanent magnetic dipole moment in the cosmic string spacetime under Lorentz symmetry breaking effects. Besides, we analyse the influence of the effects of the Lorentz symmetry violation and the topology of the defect on the Aharonov–Casher geometric quantum phase in the nonrelativistic limit.

Persistent Superfluid Flow Arising from the He-McKellar-Wilkens Effect in Molecular Dipolar Condensates.

We show that the He-McKellar-Wilkens effect can induce a persistent flow in a Bose-Einstein condensate of polar molecules confined in a toroidal trap, with the dipolar interaction mediated via an electric dipole moment. For Bose-Einstein condensates of atoms with a magnetic dipole moment, we show that although it is theoretically possible to induce persistent flow via the Aharonov-Casher effect, the strength of the electric field required is prohibitive. We also outline an experimental geometry tailored specifically for observing the He-McKellar-Wilkens effect in toroidally trapped condensates.