arXiv subjects

E. Ya. Sherman

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

At least 37 records · Page 2Linked to original sources

arXiv2020

Interlayer exciton-polaron in atomically thin semiconductors

A novel type of exciton-phonon bound state -- interlayer polaron -- in a double-layer two-dimensional semiconductor with transition metal dichalcogenides as an example, is predicted. In these systems the interaction of the interlayer exciton with the soft modes of out-of-plane lattice vibrations caused by van der Waals forces and flexural rigidity gives rise to a bound quasiparticle. The energy and effective mass of the formed polaron for weak and strong exciton-phonon coupling regimes are calculated and analyzed. Possible manifestations of these effects in transport- and spectroscopy-related experiments are discussed.

cond-mat.mtrl-sci↗

arXiv2020

Spin rotation by resonant electric field in few-level quantum dots: Floquet dynamics and tunneling

We study electric dipole spin resonance caused by sub-terahertz (THz) radiation in a multilevel finite-size quantum dot formed in a nanowire focusing on the range of driving electric fields amplitudes where a strong interplay between the Rabi spin oscillations and tunneling from the dot to continuum states can occur. A strong effect of the tunneling on the spin evolution in this regime occurs due to formation of mixed spin states. As a result, the tunneling strongly limits possible spin manipulations time. We demonstrate a backaction of the spin dynamics on the tunneling and position of the electron. The analysis of the efficiency of the spin manipulation in terms of the system energy shows that tunneling decreases this efficiency. Fourier spectra of the time-dependent expectation value of the electron position show a strong effect of the spin-orbit coupling on their low-frequency components. This results can be applied to operational properties of spin-based nanodevices and extending the range of possible spin resonance frequencies to the THz domain.

cond-mat.mes-hall↗

arXiv2020

Chaotic cyclotron and Hall trajectories due to spin-orbit coupling

We demonstrate that the synergistic effect of a gauge field, Rashba spin-orbit coupling (SOC), and Zeeman splitting can generate chaotic cyclotron and Hall trajectories of particles. The physical origin of the chaotic behavior is that the SOC produces a spin-dependent (so-called anomalous) contribution to the particle velocity and the presence of Zeeman field reduces the number of integrals of motion. By using analytical and numerical arguments, we study the conditions of chaos emergence and report the dynamics both in the regular and chaotic regimes. {We observe the critical dependence of the dynamic patterns (such as the chaotic regime onset) on small variations in the initial conditions and problem parameters, that is the SOC and/or Zeeman constants. The transition to chaotic regime is further verified by the analysis of phase portraits as well as Lyapunov exponents spectrum.} The considered chaotic behavior can occur in solid state systems, weakly-relativistic plasmas, and cold atomic gases with synthetic gauge fields and spin-related couplings.

nlin.CD↗

arXiv2019

Multidimensional hybrid Bose-Einstein condensates stabilized by lower-dimensional spin-orbit coupling

We show that attractive spinor Bose-Einstein condensates under the action of spin-orbit coupling (SOC) and Zeeman splitting form self-sustained stable two- and three-dimensional (2D and 3D) states in free space, even when SOC acts in a lower-dimensional form. We find that two-dimensional states are stabilized by one-dimensional (1D) SOC in a broad range of chemical potentials, for atom numbers (or norm of the spinor wavefunction) exceeding a threshold value, which strongly depends on the SOC strength and vanishes at a critical point. The zero-threshold point is a boundary between single-peaked and striped states, realizing hybrids combining 2D and 1D structural features. In a vicinity of such point, an asymptotic equation describing the bifurcation of the solitons from the linear spectrum is derived and investigated analytically. We show that striped 3D solitary states are as well stabilized by 2D SOC, albeit in a limited range of chemical potentials and norms.

cond-mat.quant-gas↗

arXiv2019

Quantum mechanics and speed limit of ultrafast local control in spin chains

We study optimization of fidelity for ultrafast transformation of a spin chain via external control of a local exchange coupling. We show that infidelity of such a process can be dramatically decreased by choosing a proper control profile in nonadiabatic time domain, predict main features of this profile analytically, corroborate them numerically with a gradient search algorithm, and discuss the corresponding quantum speed limit. For ultrafast transformations, the qualitative features of the obtained optimal control are system-independent. Moreover, the main restrictions on its shape do not depend on the transformation time and remain valid up to the adiabatic limit. Our results can be applied to control a broad variety of quantum systems.

quant-ph↗

arXiv2019

Solitons in inhomogeneous gauge potentials: integrable and nonintegrable dynamics

We introduce an exactly integrable nonlinear model describing the dynamics of spinor solitons in space-dependent matrix gauge potentials of rather general types. The model is shown to be gauge equivalent to the integrable system of vector nonlinear Schrödinger equations known as the Manakov model. As an example we consider a self-attractive Bose-Einstein condensate with random spin-orbit coupling (SOC). If Zeeman splitting is also included, the system becomes nonintegrable. We illustrate this by considering the random walk of a soliton in a disordered SOC landscape. While at zero Zeeman splitting the soliton moves without scattering along linear trajectories in the random SOC landscape, at nonzero splitting it exhibits strong scattering by the SOC inhomogeneities. For a large Zeeman splitting the integrability is recovered. In this sense the Zeeman splitting serves as a parameter controlling the crossover between two different integrable limits.

nlin.SI↗

arXiv2019

Electric dipole spin resonance at shallow donors in quantum wires

Electric dipole spin resonance is studied theoretically at a shallow donor formed in a nanowire with spin-orbit coupling in a magnetic field. Such system may represent a donor-based qubit. The single discrete energy level of the donor is accompanied by the set of continuum states, which provide a non-trivial interplay for the picture of electric dipole spin resonance driven by an external monochromatic field. Strongly nonlinear dependencies of spin flip time as well as of the coordinate mean values on the electric field amplitude are observed, demonstrating the significance of coupling to the continuum for spin-based qubits manipulation in nanostructures.

cond-mat.mes-hall↗

arXiv2019

Non-adiabatic transformation of a spin-chain geometry via local control

We consider transformation from a closed to an open spin chain and vice versa produced by changing single link strength in a pair of neighboring spins. We show that in the non-adiabatic time domain fidelity of such a process can be increased by proper choosing of the control function for spin-spin exchange coupling. We obtain this function for an antiferromagnetic quantum Ising chain and present heuristic reasons restricting possible time-dependences of Hamiltonians applied for a high-fidelity control.

quant-ph↗

arXiv2018

Rabi-coupling driven motion of a soliton in a Bose-Einstein condensate

We study the motion of a self-attractive Bose-Einstein condensate with pseudo-spin 1/2 driven by a synthetic Rabi (Zeeman-like) field. This field triggers the pseudo-spin dynamics resulting in a density redistribution between its components and, as a consequence, in changes of the overall density distribution. In the presence of an additional external potential, the latter produces a net force acting on the condensate and activates its displacement. As an example, here we consider the case of a one-dimensional condensate in a random potential.

cond-mat.quant-gas↗

arXiv2018

High-fidelity non-adiabatic cutting and stitching of a spin chain via local control

We propose and analyze, focusing on non-adiabatic effects, a technique of manipulating quantum spin systems based on local 'cutting' and 'stitching' of the Heisenberg exchange coupling between the spins. This first operation is cutting of a bond separating a single spin from a linear chain, or of two neighboring bonds for a ring-shaped array of spins. We show that the disconnected spin can be in the ground state with a high-fidelity even after a non-adiabatic process. Next, we consider inverse operation of stitching these bonds to increase the system size. We show that the optimal control algorithm can be found by using common numerical procedures with a simple two-parametric control function able to produce a high-fidelity cutting and stitching. These results can be applied for manipulating ensembles of quantum dots, considered as prospective elements for quantum information technologies, and for design of machines based on quantum thermodynamics.

quant-ph↗

arXiv2018

Qubit gates with simultaneous transport in double quantum dots

A single electron spin in a double quantum dot in a magnetic field is considered in terms of a four-level system. By describing the electron motion between the potential minima by spin-conserving tunneling and spin flip caused by a spin-orbit coupling, we inversely engineer faster-than-adiabatic state manipulation operations based on the geometry of four-dimensional (4D) rotations. In particular, we show how to transport a qubit among the quantum dots performing simultaneously a required spin rotation.

quant-ph↗

arXiv2018

Spin-orbit coupled soliton in a random potential

We investigate theoretically the dynamics of a spin-orbit coupled soliton formed by a self- interacting Bose-Einstein condensate immersed in a random potential, in the presence of an artificial magnetic field. We find that due to the anomalous spin-dependent velocity, the synthetic Zeeman coupling can play a critical role in the soliton dynamics by causing its localization or delocalization, depending on the coupling strength and on the parameters of the random potential. The observed effects of the Zeeman coupling qualitatively depend on the type of self-interaction in the condensate since the spin state and the self-interaction energy of the condensate are mutually related if the invariance of the latter with respect to the spin rotation is lifted.

cond-mat.quant-gas↗

arXiv2018

Energy levels repulsion by spin-orbit coupling in two-dimensional Rydberg excitons

We study the effects of Rashba spin-orbit coupling on two-dimensional Rydberg exciton systems. Using analytical and numerical arguments we demonstrate that this coupling considerably modifies the wave functions and leads to a level repulsion that results in a deviation from the Poissonian statistics of the adjacent level distance distribution. This signifies the crossover to non-integrability of the system and hints on the possibility of quantum chaos emerging. Such a behavior strongly differs from the classical realization, where spin-orbit coupling produces highly entangled, chaotic electron trajectories in an exciton. We also calculate the oscillator strengths and show that randomization appears in the transitions between states with different total momenta.

cond-mat.mes-hall↗

arXiv2018

Charge and spin conductivity of a two-dimensional electron gas with random Rashba interaction

We calculate the transport relaxation time $τ_{\rm tr}$ and spin transport relaxation time $τ_{s,{\rm tr}}$ for a two-dimensional electron gas with spatially fluctuating Rashba spin-orbit interaction. These relaxation times determine the electrical and spin conductivity of the two-dimensional system, respectively. It is shown that the transport relaxation time $τ_{\rm tr}$ is a nonmonotonic function of electron energy $\varepsilon $, whereas the spin transport relaxation time $τ_{s,{\rm tr}}$ decreases with increasing $\varepsilon $, similarly to the conventional electron relaxation time $τ$ that characterizes the decay of an electron state corresponding to certain values of the momentum and spin. Such a behavior of the relaxation times leads to unusual temperature dependence of the electrical and spin conductivity.

cond-mat.mes-hall↗

arXiv2018

Theory of the inverse spin galvanic effect in quantum wells

The understanding of the fundamentals of spin and charge densities and currents interconversion by spin-orbit coupling can enable efficient applications beyond the possibilities offered by conventional electronics. For this purpose we consider various forms of the frequency-dependent inverse spin galvanic effect (ISGE) in semiconductor quantum wells and epilayers taking into account the cubic in the electron momentum spin-orbit coupling in the Rashba and Dresselhaus forms, concentrating on the current-induced spin polarization (CISP). We find that including the cubic terms qualitatively explains recent findings of the CISP in InGaAs epilayers being the strongest if the internal spin-orbit coupling field is the smallest and vice versa (Norman et . 2014, Luengo et al. 2017), in contrast to the common understanding. Our results provide a promising framework for the control of spin transport in future spintronics devices.

cond-mat.mes-hall↗

arXiv2018

Inverse engineering for fast transport and spin control of spin-orbit-coupled Bose-Einstein condensates in moving harmonic traps

We investigate fast transport and spin manipulation of tunable spin-orbit-coupled Bose-Einstein condensates in a moving harmonic trap. Motivated by the concept of "shortcuts to adiabaticity", we design inversely the time-dependent trap position and spin-orbit coupling strength. By choosing appropriate boundary conditions we obtain fast transport and spin flip simultaneously. The non-adiabatic transport and relevant spin dynamics are illustrated with numerical examples, and compared with the adiabatic transport with constant spin-orbit-coupling strength and velocity. Moreover, the influence of nonlinearity induced by interatomic interaction is discussed in terms of the Gross-Pitaevskii approach, showing the robustness of the proposed protocols. With the state-of-the-art experiments, such inverse engineering technique paves the way for coherent control of spin-orbit-coupled Bose-Einstein condensates in harmonic traps.

quant-ph↗

arXiv2017

Chaos in two-dimensional Kepler problem with spin-orbit coupling

We consider classical two-dimensional Kepler system with spin-orbit coupling and show that at a sufficiently strong coupling it demonstrates a chaotic behavior. The chaos emerges since the spin-orbit coupling reduces the number of the integrals of motion as compared to the number of the degrees of freedom. This reduction is manifested in the equations of motion as the emergence of the anomalous velocity determined by the spin orientation. By using analytical and numerical arguments, we demonstrate that the chaotic behavior, being driven by this anomalous term, is related to the system energy dependence on the initial spin orientation. We observe the critical dependence of the dynamics on the initial conditions, where system can enter and exit a stability domain by very small changes in the initial spin orientation. Thus, this system can demonstrate a reentrant order-from-disorder transition driven by very small variations in the initial conditions.

cond-mat.mes-hall↗

arXiv2017

Uniform magnetization dynamics of a submicron ferromagnetic coin driven by the spin-orbit coupled spin torque

A simple model of magnetization dynamics in a ferromagnet/doped semiconductor hybrid structure with Rashba spin-orbit interaction (SOI) driven by an applied pulse of the electric field is proposed. The electric current excited by the applied field is spin-polarized due to the SOI and therefore it induces the magnetization rotation in the ferromagnetic layer via s-d exchange coupling. Magnetization dynamics dependence on the electric pulse shape and magnitude is analyzed for realistic values of parameters. We show that it is similar to the dynamics of a damped nonlinear oscillator with the time-dependent frequency proportional to the square root of the applied electric field. The magnetization switching properties of an elliptic magnetic element are examined as a function of the applied field magnitude and direction.

cond-mat.mes-hall↗