Photo-induced, non-equilibrium spin and charge polarization in quantum rings

TL;DR

This paper explores how linearly polarized electromagnetic pulses induce spin and charge polarization in quantum rings with spin-orbit interaction, revealing controllable non-equilibrium dynamics and potential applications in nano-electronic devices.

Contribution

It demonstrates the control of spin and charge polarization in quantum rings using electromagnetic pulses and static magnetic flux, highlighting new ways to manipulate quantum states in nanoscale systems.

Findings

Pulse-induced spin-split charge density oscillates with spin-orbit strength.

Emission spectrum can be tuned via pulse strength or gate voltage.

Static magnetic flux modifies non-equilibrium spin and charge dynamics.

Abstract

We investigate the spin-dependent dynamical response of a quantum ring with a spin-orbit interaction upon the application of linearly polarized, picosecond, asymmetric electromagnetic pulses. The oscillations of the generated dipole moment are sensitive to the parity of the occupation number in the ring and to the strength of the spin-orbit coupling. It is shown how the associated emission spectrum can be controlled via the pulse strength or a gate voltage. In addition, we inspect how a static magnetic flux can modify the non-equilibrium dynamics. In presence of the spin-orbit interaction and for a paramagnetic ring, the applied pulse results in a spin-split, non-equilibrium local charge density. The resulting temporal spin polarization is directed perpendicular to the light-pulse polarization axis and oscillates periodically with the frequency of the spin-split charge density. The spin-averaged non-equilibrium charge density possesses a left-right symmetry with respect to the pulse polarization axis. The calculations presented here are applicable to nano-meter rings fabricated in heterojuctions of III-V and II-VI semiconductors containing several hundreds electrons.