arXiv subjects

E. B. Sonin

Publications and source records attributed to E. B. Sonin.

At least 37 records · Page 2Linked to original sources

arXiv2011

Quantum spin Hall effect in 2D topological insulators

The original motivation of great interest to topological insulators was the hope to observe the quantum spin Hall effect. Therefore if a material is in the topological insulator state they frequently call it the quantum spin Hall state. However, despite impressive experimental results confirming the existence of the quantum spin Hall state, the quantum spin Hall effect has not yet been detected. After a short overview of what was originally suggested as the quantum spin Hall effect (quantum spin conductance determined by the topological Chern number) the paper analyzes the crucial role of the boundary condition on the observation of the effect and finally discusses whether and how the quantum spin Hall effect could be observed.

cond-mat.mes-hall↗

arXiv2011

Equilibrium rotation of a vortex bundle terminating on a lateral wall

The paper investigates possibility of equilibrium solid-body rotation of a vortex bundle diverging at some height from a cylinder axis and terminating on a lateral wall of a container. Such a bundle arises when vorticity expands up from a container bottom eventually filling the whole container. The analysis starts from a single vortex, then goes to a vortex sheet, and finally addresses a multi-layered crystal vortex bundle. The equilibrium solid-body rotation of the vortex bundle requires that the thermodynamic potentials in the vortex-filled and in the vortex-free parts of the container are equal providing the absence of a force on the vortex front separating the two parts. The paper considers also a weakly non-equilibrium state when the bundle and the container rotate with different angular velocities and the vortex front propagates with the velocity determined by friction between vortices and the container or the normal liquid moving together with the container.

cond-mat.other↗

arXiv2010

Edge accumulation and currents of moment in 2D topological insulators

The Letter is analyzing bulk spin (moment) currents and spin (moment) accumulation at edges of a 2D topological insulator taking into account reflection from edges. Accumulation occurs only at edge states, which distinguish topological insulators from conventional ones. The band continuum can support the transverse bulk spin (moment) current, but it does not governed by the topological Chern number and may exist in a conventional insulator. There is no edge accumulation related with bulk currents.

cond-mat.mes-hall↗

arXiv2010

Shape-dependent Depinning of a Domain Wall by a Magnetic Field and a Spin-Polarized Current

The effect of sample shape on the depinning of the domain wall (DW) driven by an applied magnetic field or a spin-polarized current is studied theoretically. The shape effect resulting from the modulation of the sample width (geometric pinning) can essentially affect the DW depinning. We found a good agreement between the ratios of the critical values of the magnetic field and the spin-polarized current predicted by the theory and measured in the experiment.

cond-mat.other↗

arXiv2010

Spin currents and spin superfluidity

The present review analyzes and compares various types of dissipationless spin transport: (1) Superfluid transport, when the spin-current state is a metastable state (a local but not the absolute minimum in the parameter space). (2) Ballistic spin transport, when spin is transported without losses simply because sources of dissipation are very weak. (3) Equilibrium spin currents, i.e., genuine persistent currents. (4) Spin currents in the spin Hall effect. Since superfluidity is frequently connected with Bose condensation, recent debates about magnon Bose condensation are also reviewed. For any type of spin currents simplest models were chosen for discussion in order to concentrate on concepts rather than details of numerous models. The various hurdles on the way of using the concept of spin current (absence of the spin-conservation law, ambiguity of spin current definition, etc.) were analyzed. The final conclusion is that the spin-current concept can be developed in a fully consistent manner, and is a useful language for description of various phenomena in spin dynamics.

cond-mat.other↗

arXiv2010

Supercurrent in superconducting graphene

The problem of supercurrent in superconducting graphene is revisited and the supercurrent is calculated within the mean-field model employing the two-component wave functions on a honeycomb lattice with pairing between different valleys in the Brillouin zone. We show that the supercurrent within the linear approximation in the order-parameter-phase gradient is always finite even if the doping level is exactly zero.

cond-mat.supr-con↗

arXiv2009

Edge spin accumulation: spin Hall effect without bulk spin current

Spin accumulation in a 2D electron gas with Rashba spin-orbit interaction subject to an electric field can take place without bulk spin currents (edge spin Hall effect). This is demonstrated for the collisional regime using the non-equilibrium distribution function determined from the standard Boltzmann equation. Spin accumulation originates from interference of incident and reflected electron waves at the sample boundary.

cond-mat.mes-hall↗

arXiv2009

Effect of Klein tunneling on conductance and shot noise in ballistic graphene

The conductance and the Fano factor in a graphene sheet in the ballistic regime are calculated. The electrostatic potential in the sheet is modeled by a trapezoid barrier, which allows to use the exact solution of the Dirac equation in a uniform electric field in the slope areas (the two lateral sides of the trapezoid). A special attention is devoted to asymmetry with respect to the sign of the gate voltage, which is connected with the difference between the Klein tunneling and the over-barrier reflection. The comparison of the developed theory with the experiment supports the conclusion that the Klein tunneling was revealed experimentally.

cond-mat.mes-hall↗

arXiv2008

Gauge-field rotation of 2D exciton Bose condensate in double quantum well by radial magnetic field

Here it is shown that a radial magnetic field leads to rotation of a Bose condensed exciton cloud due to Aharonov-Bohm effect for an electron and a hole forming an exciton. As in the case of mechanical rotation of superfluids, rotation is accompanied by penetration of vortices into the cloud at some critical magnetic field. Penetration of vortices strongly affects the total intensity and the angular distribution of photoluminescence from the exciton cloud. This effect can be used for an effective experimental manifestation of exciton Bose condensation.

cond-mat.other↗

arXiv2008

Domain Walls in a Tetragonal Chiral p-Wave Superconductor

Domain walls in a tetragonal chiral p-wave superconductors with broken time reversal symmetry are analyzed in the framework of the Ginsburg-Landau theory. The energy and the jump of the magnetic induction on the wall were determined for different types of walls as functions of the parameters of the Ginzburg-Landau theory and orientation of the domain wall with respect to the crystallographic axes. We discuss implications of the analysis for $Sr_{2}RuO_{4}$, where no stray magnetic fields from domain walls were detected experimentally.

cond-mat.supr-con↗

arXiv2008

Spin-precession vortex and spin-precession supercurrent stability in $^3$He-B

The Letter analyzes stability of spin precession currents in superfluid $^3$He-B when the precession angle is very close to 104$^\circ$. In this limit a spin-precession vortex has a very large core, and a barrier blocking motion of these large-core vortices across the current streamlines (phase slip) disappears at precession-phase gradients much smaller than critical gradients estimated from the Landau criterion. Nevertheless, spin precession currents remain stable up to the Landau critical gradients, since in this case there is a barrier, which blocks the phase slip at very early stage of vortex-core nucleation. The Letter also predicts a second-order phase transition between a parity-symmetric and parity-nonsymmetric spin-precession vortex cores at the precession angle 126.5$^\circ$.

cond-mat.other↗

arXiv2008

Charge transport and shot noise in ballistic graphene sheet

The current and the shot noise in a graphene sheet were analyzed in the ballistic regime for arbitrary voltage drops between leads and the sheet in the limit of infinite aspect ratio of the sheet width to its length, when quantization of transversal wave vectors is not essential. The cases of coherent and incoherent ballistic transport were compared. At high voltages the difference with coherent transport is not essential. But at low voltages conductance and Fano-factor dependences for incoherent transport become non-monotonous so that the conductance has a minimum and the Fano factor has a maximum at non-zero voltage bias.

cond-mat.mes-hall↗

arXiv2008

BCS superconductivity of Dirac electrons in graphene layers

Possible superconductivity of electrons with the Dirac spectrum is analyzed using the BCS model. We calculate the critical temperature, the superconducting energy gap, and supercurrent as functions of the doping level and of the pairing interaction strength. Zero doping is characterized by existence of the quantum critical point such that the critical temperature vanishes below some finite value of the interaction strength. However, the critical temperature remains finite for any nonzero electron or hole doping level when the Fermi energy is shifted away from the Dirac point of the normal-state electron spectrum. We analyze the behavior of the characteristic length scales, i.e., the London penetration depth and the coherence length, which determine the critical magnetic fields.

cond-mat.supr-con↗

arXiv2008

Cryptoferromagnetism in Superconductors with Broken Time-Reversal Symmetry

The cryptoferromagnetic state (the state with intrinsic domain structure) in superconducting ferromagnets subjected to external magnetic field is studied theoretically. Ferromagnetism originates either from electron spin or the intrinsic angular momentum of Cooper pairs (chiral p-wave superconductors like $\mathrm{Sr_2 Ru O_4}$). The phase transitions towards the Meissner and the mixed states are investigated, and the magnetic phase diagrams are obtained. Cryptoferromagnetism, as a form coexistence of superconductivity and ferromagnetism, can be detected by observation of magnetization curves predicted in the present analysis.

cond-mat.supr-con↗

arXiv2007

Dynamics of coreless vortices and rotation-induced dissipation peak in superfluid films on rotating porous substrates

We analyze dynamics of 3D coreless vortices in superfluid films covering porous substrates. The 3D vortex dynamics is derived from the 2D dynamics of the film. The motion of a 3D vortex is a sequence of jumps between neighboring substrate cells, which can be described, nevertheless, in terms of quasi-continuous motion with average vortex velocity. The vortex velocity is derived from the dissociation rate of vortex-antivortex pairs in a 2D film, which was developed in the past on the basis of the Kosterlitz-Thouless theory. The theory explains the rotation-induced dissipation peak in torsion-oscillator experiments on $^4$He films on rotating porous substrates and can be used in the analysis of other phenomena related to vortex motion in films on porous substrates.

cond-mat.soft↗

arXiv2007

Mechanical measurement of equilibrium spin currents in the Rashba medium

We demonstrate that an equilibrium spin current in a 2D electron gas with Rashba spin-orbit interaction (Rashba medium) results in a mechanical torque on a substrate near an edge of the medium. If the substrate is a cantilever, the mechanical torque displaces the free end of the cantilever. The effect can be enhanced and tuned by a magnetic field. Observation of this displacement would be an effective method to prove existence of equilibrium spin currents. The analysis of edges of the Rashba medium demonstrates the existence of localized edge states. They form a 1D continuum of states. This suggests a new type of quantum wire: spin-orbit quantum wire.

cond-mat.mes-hall↗

arXiv2007

Equilibrium spin currents in the Rashba medium

We analyze equilibrium spin currents in a 2D electron gas with Rashba spin-orbit interaction (Rashba medium). In a uniform Rashba medium these currents are constant, and their ability to really transport spin is not evident. But even weak inhomogeneity of the Rashba medium allows to reveal that equilibrium spin currents can transport spin from areas where spin is produced to areas where spin is absorbed.

cond-mat.mes-hall↗

arXiv2006

Domain-Wall Waves (2D Magnons) in Superconducting Ferromagnets

Propagation of the magnetization waves along domain walls (2D magnons) in a superconducting ferromagnet has been studied theoretically. The magnetostatic fields (long-range dipole-dipole interaction) have a crucial effect on the spectrum of 2D magnons. But this effect is essentially affected by the superconducting Meissner currents, which screen the magnetostatic fields and modify the long-wavelength spectrum from square-root to linear. The excitation of the domain wall waves by an electromagnetic wave incident on a superconducting-ferromagnet sample has been considered. This suggests using measurements of the surface impedance for studying the domain wall waves, and eventually for effective probing of superconductivity-ferromagnetism coexistence.

cond-mat.supr-con↗