D. C. Marinescu

Electronic Charge and Spin Density Distribution in a Quantum Ring with Spin-Orbit and Coulomb Interactions

Charge and spin density distributions are studied within a nano-ring structure endowed with Rashba and Dresselhaus spin orbit coupling (SOI). For a small number of interacting electrons, in the presence of an external magnetic field, the energy spectrum of the system is calculated through an exact numerical diagonalization procedure. The eigenstates thus determined are used to estimate the charge and spin densities around the ring. We find that when more than two electrons are considered, the charge-density deformations induced by SOI are dramatically flattened by the Coulomb repulsion, while the spin density ones are amplified.

Nonadiabatic Generation of a Pure Spin Current in a One-Dimensional Quantum Ring with Spin-Orbit Interaction

We demonstrate the theoretical possibility of obtaining a pure spin current in a 1D ring with spin-orbit interaction by irradiation with a non-adiabatic, two-component terahertz laser pulse, whose spatial asymmetry is reflected by an internal dephasing angle

Coulomb interaction effects on the Majorana states in quantum wires

phi

Persistent oscillatory currents in a 1D ring with Rashba and Dresselhaus spin–orbit interactions excited by a terahertz pulse

. The stationary solutions of the equation of motion for the density operator are obtained for a spin-orbit coupling linear in the electron momentum (Rashba) and used to calculate the time-dependent charge and spin currents. We find that there are critical values of

Nonadiabatic generation of spin currents in a quantum ring with Rashba and Dresselhaus spin-orbit interactions

phi

Coulomb Interaction Effects on the Spin Polarization and Currents in Quantum Wires with Spin Orbit Interaction

at which the charge current disappears, while the spin current reaches a maximum or a minimum value.

Friedel oscillations in a lateral superlattice with spin-orbit interaction

The stability of the Majorana modes in the presence of a repulsive interaction is studied in the standard semiconductor wire-metallic superconductor configuration. The effects of short-range Coulomb interaction, which is incorporated using a purely repulsive δ-function to model the strong screening effect due to the presence of the superconductor, are determined within a Hartree-Fock approximation of the effective Bogoliubov-De Gennes Hamiltonian that describes the low-energy physics of the wire. Through a numerical diagonalization procedure we obtain interaction corrections to the single particle eigenstates and calculate the extended topological phase diagram in terms of the chemical potential and the Zeeman energy. We find that, for a fixed Zeeman energy, the interaction shifts the phase boundaries to a higher chemical potential, whereas for a fixed chemical potential this shift can occur either at lower or higher Zeeman energies. These effects can be interpreted as a renormalization of the g-factor due to the interaction. The minimum Zeeman energy needed to realize Majorana fermions decreases with the increasing strength of the Coulomb repulsion. Furthermore, we find that in wires with multi-band occupancy this effect can be enhanced by increasing the chemical potential, i.e. by occupying higher energy bands.

Antiferromagnetic order in a semiconductor quantum well with spin–orbit coupling

Abstract Persistent, oscillatory charge and spin currents are shown to be driven by a two-component terahertz laser pulse in a one-dimensional mesoscopic ring with Rashba and Dresselhaus spin–orbit interactions (SOI) linear in the electron momentum. The characteristic interference effects result from the opposite precession directions imposed on the electron spin by the two SOI couplings. The time dependence of the currents is obtained by solving numerically the equation of motion for the density operator, which is later employed in calculating statistical averages of quantum operators on few electron eigenstates. The parameterization of the problem is done in terms of the SOI coupling constants and of the phase difference between the two laser components. Our results indicate that the amplitude of the oscillations is controlled by the relative strength of the two SOIs, while their frequency is determined by the difference between the excitation energies of the electron states. Furthermore, the oscillations of the spin current acquire a beating pattern of higher frequency that we associate with the nutation of the electron spin between the quantization axes of the two SOI couplings. This phenomenon disappears at equal SOI strengths, whereby the opposite precessions occur with the same probability.

Anomalous spin and charge Seebeck effect in a quantum well with spin orbit interaction

When subjected to a linearly polarized terahertz pulse, a mesoscopic ring endowed with spin-orbit interaction (SOI) of the Rashba-Dresselhaus type exhibits non-uniform azimuthal charge and spin distributions. Both types of SOI couplings are considered linear in the electron momentum. Our results are obtained within a formalism based on the equation of motion satisfied by the density operator which is solved numerically for different values of the angle , the angle determining the polarization direction of the laser pulse. Solutions thus obtained are later employed in determining the time-dependent charge and spin currents, whose values are calculated in the stationary limit. Both these currents exhibit an oscillatory behavior complicated in the case of the spin current by a beating pattern. We explain this occurrence on account of the two spin-orbit interactions which force the electron spin to oscillate between the two spin quantization axes corresponding to Rashba and Dresselhaus interactions. The oscillation frequencies are explained using the single particle spectrum.

Quasiparticle lifetime in a bilayer system

Abstract We analyze the charge and spin distributions induced in an interacting electron system confined inside a semiconductor quantum wire with spin orbit interaction in the presence of an external magnetic field. The wire, assumed to be infinitely long, is obtained through lateral confinement in three different materials: GaAs, InAs, and InSb. The spin-orbit coupling, linear in the electron momentum is of both Rashba and Dresselhaus type. Within the Hartree-Fock approximation the many-body Hamiltonian is diagonalized directly and its eigenfunctions and single-particle spectra are obtained selfconsistently. Further, we calculate charge, and spin densities, as well as the charge and spin currents and compare them with those obtained in the absence of the interaction. Thus we observe an enhancement of the spin polarization associated with the spin-orbit intreractions, on account of the exchange Coulomb effects, in GaAs, but not in InAs and InSb. However, in the later materials the direct Coulomb interaction may amplify or modify the spin currents.