arXiv subjects

E. Ya. Sherman

Publications and source records attributed to E. Ya. Sherman.

At least 73 records · Page 4Linked to original sources

arXiv2013

Spin Chaos Manifestation in a Driven Quantum Billiard with Spin-Orbit Coupling

The coupling of orbital and spin degrees of freedom is the source of many interesting phenomena. Here, we study the electron dynamics in a quantum billiard --a mesoscopic rectangular quantum dot-- with spin-orbit coupling driven by a periodic electric field. We find that both the spatial and temporal profiles of the observables demonstrate the transition to chaotic dynamics with qualitative modifications of the power spectra and patterns of probability and spin density. The time dependence of the wavefunctions and spin density distributions indicates spin-charge separation {seen in the decay of the spin-charge density correlators}. This new spin chaos effect can be experimentally verified leading to a better understanding of the interplay between spin and spatial degrees of freedom, relevant to fundamental and applied quantum physics.

cond-mat.mes-hall↗

arXiv2013

Effect of gate-driven spin resonance on the conductance of a one-dimensional quantum wire

We consider quasiballistic electron transmission in a one-dimensional quantum wire subject to both time-independent and periodic potentials of a finger gate that results in a coordinate- and time-dependent Rashba-type spin-orbit coupling. A spin-dependent conductance is calculated as a function of external constant magnetic field, the electric field frequency, and the potential strength. The results demonstrate the effect of the gate-driven electric dipole spin resonance in a transport phenomenon such as spin-flip electron transmission.

cond-mat.mes-hall↗

arXiv2013

Spin noise of exciton-polaritons in microcavities

We develop a theory of spin fluctuations of exciton-polaritons in a semiconductor microcavity under the non-resonant unpolarized pumping. It is shown that the corresponding spin noise is sensitive to the scattering rates in the system, occupation of the ground state, statistics of polaritons, and interactions. The spin noise spectrum drastically narrows in the polariton lasing regime due to formation of a polariton condensate, while its shape can become non-Lorentzian owing to interaction-induced spin decoherence.

cond-mat.mes-hall↗

arXiv2013

Relaxation of flying spin qubits in quantum wires by hyperfine interaction

We consider the relaxation of a spin qubit in a quantum dot propagating as a whole in a one-dimensional semiconductor with hyperfine coupling. We show that this motion leads to qualitatively new features in this process compared to static quantum dots. For a fast straightforward motion, the initial spin density decreases to zero with the relaxation rate independent of the spatial spread of the electron wave function and inversely proportional to the electron speed. However, for the oscillatory motion, the qubit acquires memory, and the dephasing becomes Gaussian rather than exponential. After some time, one third of the initial spin polarization is restored, as it happens for static qubits. This revival can occur either through periodic peaks or through a monotonous increase in the polarization, after a minimum, until a plateau has been reached. Our results can be useful for the understanding of the spin dynamics and decoherence in quantum wires.

cond-mat.mes-hall↗

arXiv2013

Spin dynamics of cold fermions with synthetic spin-orbit coupling

We consider spin relaxation dynamics in cold Fermi gases with a pure-gauge spin-orbit coupling corresponding to recent experiments. We show that such experiments can give a direct access to the collisional spin drag rate, and establish conditions for the observation of spin drag effects. In the recent experiments the dynamics is found to be mainly ballistic leading to new regimes of reversible spin relaxation-like processes.

cond-mat.quant-gas↗

arXiv2012

Spin dynamics in tunneling decay of a metastable state

We analyze spin dynamics in the tunneling decay of a metastable localized state in the presence of spin-orbit coupling. We find that the spin polarization at short time scales is affected by the initial state while at long time scales both the probability- and the spin density exhibit diffraction-in-time phenomenon. We find that in addition to the tunneling time the tunneling in general can be characterized by a new parameter, the tunneling length. Although the tunneling length is independent on the spin-orbit coupling, it can be accessed by the spin rotation measurement.

quant-ph↗

arXiv2012

Nonlinear anomalous Hall effect and negative magnetoresistance in a system with random Rashba field

We predict two spin-dependent transport phenomena in two-dimensional electron systems, which are induced by spatially fluctuating Rashba spin-orbit interaction. When the electron gas is magnetized, the random Rashba interaction leads to the anomalous Hall effect. An example of such a system is a narrow-gap magnetic semiconductor-based symmetric quantum well. We show that the anomalous Hall conductivity reveals a strongly nonlinear dependence on the magnetization, decreasing exponentially at large spin density. We also show that electron scattering from a fluctuating Rashba field in a two-dimensional nonmagnetic electron system leads to a negative magnetoresistance arising solely due to spin-dependent effects.

cond-mat.mes-hall↗

arXiv2012

The effects of disorder in dimerized quantum magnets in mean field approximations

We study theoretically the effects of disorder on Bose-Einstein condensates (BEC) of bosonic triplon quasiparticles in doped dimerized quantum magnets. The condensation occurs in a strong enough magnetic field Hc, where the concentration of bosons in the random potential is sufficient to form the condensate. The effect of doping is partly modeled by delta - correlated disorder potential, which (i) leads to the uniform renormalization of the system parameters and (ii) produces disorder in the system with renormalized parameters. These approaches can explain qualitatively the available magnetization data in the Tl_(1-x)K_(x)CuCl_3 compound taken as an example. In addition to the magnetization, we found that the speed of the Bogoliubov mode has a peak as a function of doping parameter, x. No evidence of the pure Bose glass phase has been obtained in the BEC regime.

cond-mat.quant-gas↗

arXiv2012

Spin freezing by Anderson localization in one-dimensional semiconductors

One-dimensional quantum wires are considered as prospective elements for spin transport and manipulation in spintronics. We study spin dynamics in semiconductor GaAs-like nanowires with disorder and spin-orbit interaction by using a rotation in the spin subspace gauging away the spin-orbit field. If the disorder is sufficiently strong, the spin density after a relatively short relaxation time reaches a plateau. This effect is a manifestation of the Anderson localization and depends in a universal way on the disorder and the spin-orbit coupling strength. As a result, at a given disorder, semiconductor nanowires can permit a long-term spin polarization tunable with the spin-orbit interactions.

cond-mat.mes-hall↗

arXiv2012

Spin dynamics in a strongly driven system: very slow Rabi oscillations

We consider joint effects of tunneling and spin-orbit coupling on driven by electric field spin dynamics in a double quantum dot with a multi-level resonance scenario. We demonstrate that tunneling plays the crucial role in the formation of the Rabi-like spin-flip transitions. In contrast to the linear behavior for weak electric fields, the spin flip rate becomes much smaller than expected for the two-level model and shows oscillating dependence on the driving field amplitude in stronger fields. In addition, the full spin flip is very difficult to achieve in a multi-level resonant system. These two effects have a similarity with the Zeno effect of slowing down the dynamics of an observable by its measurement. As a result, spin manipulation by electric field becomes much less efficient than expected.

cond-mat.mes-hall↗

arXiv2012

Spin-dependent electron transport in waveguide with continuous shape

We study effects of the shape of a two-dimensional waveguide on the spin-dependent electron transport in the presence of spin-orbit coupling. The transition from classical motion to the tunneling regime can be controlled there by modulating the strength of spin-orbit coupling if the waveguide has a constriction. The spin precession strongly depends on the shape of the waveguide.

cond-mat.mes-hall↗

arXiv2012

Anisotropic spin relaxation revealed by resonant spin amplification in (110) GaAs quantum wells

We have studied spin dephasing in a high-mobility two-dimensional electron system (2DES), confined in a GaAs/AlGaAs quantum well grown in the [110] direction, using the resonant spin amplification (RSA) technique. From the characteristic shape of the RSA spectra, we are able to extract the spin dephasing times (SDT) for electron spins aligned along the growth direction or within the sample plane, as well as the $g$ factor. We observe a strong anisotropy in the spin dephasing times. While the in-plane SDT remains almost constant as the temperature is varied between 4 K and 50 K, the out-of-plane SDT shows a dramatic increase at a temperature of about 25 K and reaches values of about 100 ns. The SDTs at 4 K can be further increased by additional, weak above-barrier illumination. The origin of this unexpected behavior is discussed, the SDT enhancement is attributed to the redistribution of charge carriers between the electron gas and remote donors.

cond-mat.mtrl-sci↗

arXiv2011

Second-harmonic generation induced by electric currents in GaAs

We demonstrate a new, nonlinear optical effect of electric currents. First, a steady current is generated by applying a voltage on a doped GaAs crystal. We demonstrate that this current induces second-harmonic generation of a probe laser pulse. Second, we optically inject a transient current in an undoped GaAs crystal by using a pair of ultrafast laser pulses, and demonstrate that it induces the same second-harmonic generation. In both cases, the induced second-order nonlinear susceptibility is proportional to the current density. This effect can be used for nondestructive, noninvasive, and ultrafast imaging of currents. These advantages are illustrated by the real-time observations of a coherent plasma oscillation and spatial resolution of current distribution in a device. This new effect also provides a mechanism for electrical control of the optical response of materials.

cond-mat.mtrl-sci↗

arXiv2011

Theory of spin noise in nanowires

We develop a theory of spin noise in semiconductor nanowires considered as prospective elements for spintronics. In these structures spin-orbit coupling can be realized as a random function of coordinate correlated on the spatial scale of the order of 10 nm. By analyzing different regimes of electron transport and spin dynamics, we demonstrate that the spin relaxation can be very slow and the resulting noise power spectrum increases algebraically as frequency goes to zero. This effect makes spin effects in nanowires best suitable for studies by rapidly developing spin-noise spectroscopy.

cond-mat.mes-hall↗

arXiv2011

Spin-orbital phase synchronization in the magnetic field-driven electron dynamics in a double quantum dot

We study the dynamics of an electron confined in a one-dimensional double quantum dot in the presence of driving external magnetic fields. The orbital motion of the electron is coupled to the spin dynamics by spin orbit interaction of the Dresselhaus type. We derive an effective time-dependent Hamiltonian model for the orbital motion of the electron and obtain a synchronization condition between the orbital and the spin dynamics. From this model we deduce an analytical expression for the Arnold tongue and propose an experimental scheme for realizing the synchronization of the orbital and spin dynamics.

nlin.CD↗

arXiv2011

Measurement of non-commuting spin components using spin-orbit interaction

We analyze the physical meaning of a possible experiment aimed at the simultaneous measurement of two non-commuting spin components. We demonstrate that switching of a strong spin-orbit interaction, e.g., in a solid state or a cold-atom system, for a short period of time simulates a simultaneous von Neumann measurement of spin components, $σ_x$ and $σ_y$. By mapping spin dynamics onto coordinate-space motion, such a measurement determines time averages of $σ_x$ and $σ_y$ which, unlike their instantaneous values, may be evaluated simultaneously to an arbitrary accuracy.

quant-ph↗

arXiv2011

Macroscopic properties of triplon Bose-Einstein condensates

Magnetic insulators can be characterized by a gap separating the singlet ground state from the lowest energy triplet, S=1 excitation. If the gap can be closed by the Zeeman interaction in applied magnetic field, the resulting S=1 quasiparticles, triplons, can have concentrations sufficient to undergo the Bose-Einstein condensates transition. We consider macroscopic properties of the triplon Bose-Einstein condensates in the Hartree-Fock-Bogoliubov approximation taking into account the anomalous averages. We prove that these averages play the qualitative role in the condensate properties. As a result, we show that with the increase in the external magnetic field at a given temperature, the condensate demonstrates an instability related to the appearance of nonzero phonon damping and a change in the characteristic dependence of the speed of sound on the magnetic field. The calculated magnetic susceptibility diverges when the external magnetic field approaches this instability threshold, providing a tool for the experimental verification of this approach.

cond-mat.quant-gas↗

arXiv2011

Nonlinear spin Hall effect in GaAs (110) quantum wells

We consider stationary spin current in a (110)-oriented GaAs-based symmetric quantum well due to a nonlinear response to an external periodic electric field. The model assumed includes the Dresselhaus spin-orbit interaction and the random Rashba spin-orbit coupling. The Dresselhaus term is uniform in the quantum well plane and gives rise to spin splitting of the electron band. The external electric field of frequency $ω$ - in the presence of random Rashba coupling -- leads to virtual spin-flip transitions between spin subbands, generating stationary pure spin current proportional to the square of the field amplitude.

cond-mat.mtrl-sci↗