Spin relaxation in Rashba rings

Spin relaxation dynamics in rings with Rashba spin-orbit coupling is investigated using spin kinetic equation. We find that the spin relaxation in rings occurs toward a persistent spin configuration whose final shape depends on the initial spin polarization profile. As an example, it is shown that a homogeneous parallel to the ring axis spin polarization transforms into a persistent crown-like spin structure. It is demonstrated that the ring geometry introduces a geometrical contribution to the spin relaxation rate speeding up the transient dynamics. Moreover, we identify several persistent spin configurations as well as calculate the Green function of spin kinetic equation

Dynamics of Spin Relaxation near the Edge of Two-Dimensional Electron Gas

We report calculations of spin relaxation dynamics of two-dimensional electron gas with spin-orbit interaction at the edge region. It is found that the relaxation of spin polarization near the edge is more slow than relaxation in the bulk. That results finally in the spin accumulation at the edge. Time dependence of spin polarization density is calculated analytically and numerically. The mechanism of slower spin relaxation near the edge is related to electrons reflections from the boundary and the lack of the translation symmetry. These reflections partially compensate electron spin precession generated by spin-orbit interaction, consequently making the spin polarization near the edge long living. This effect is accompanied by spin polarization oscillations and spin polarization transfer from the perpendicular to in-plane component

Spin Photovoltaic Effect in Quantum Wires with Rashba Interaction

We propose a mechanism for spin polarized photocurrent generation in quantum wires. The effect is due to the combined effect of Rashba spin-orbit interaction, external magnetic field and microwave radiation. The time-independent interactions in the wire give rise to a spectrum asymmetry in k-space. The microwave radiation induces transitions between spin-splitted subbands, and, due to the peculiar energy dispersion relation, charge and spin currents are generated at zero bias voltage. We demonstrate that the generation of pure spin currents is possible under an appropriate choice of external control parameters

Radiation-induced current in quantum wires with side-coupled nano-rings

Photocurrent generation is studied in a system composed of a quantum wire with side-coupled quantum rings. The current generation results from the interplay of the particular geometry of the system and the use of circularly polarized radiation. We study the energy-momentum conservation for optical transitions involving electrons moving forwards and backwards in the wire. Due to the lack of time-reversal symmetry in the radiation, the optical transitions depend on the direction of motion of the electrons, leading to a current at zero bias voltage. The photocurrent increases with the number of rings within a wide range of physical parameters. A weak non-linear dependence of the current in the number of rings, related to quantum interference effects, is also predicted. This geometry suggests a scalable method for the generation of sizeable photocurrents based on nanoscale components.Comment: 7 pages, 6 figure