Spin dynamics in semiconductors in the streaming regime

TL;DR

This paper explores how spin dynamics are affected in semiconductors under the streaming regime, revealing enhanced spin effects and oscillations due to electric fields and optical excitation, with implications for spintronics.

Contribution

It introduces a theoretical framework combining spin physics with hot-electron transport in the streaming regime, highlighting novel spin phenomena and oscillations.

Findings

Spin relaxation is significantly modified in the streaming regime.

Current-induced spin orientation is greatly enhanced.

Spin oscillations are induced by spin-orbit splitting and electric fields.

Abstract

We present results of a cross-disciplinary theoretical research at the interface of spin physics and hot-electron transport. A moderately strong electric field is assumed to provide the streaming regime where each free charge carrier, an electron or a hole, accelerates quasiballistically in the "passive" region until reaching the optical-phonon energy, then emits an optical phonon and starts the next period of acceleration. The inclusion of spin degree of freedom into the streaming-regime kinetics gives rise to rich and interesting spin-related phenomena. Firstly, in the streaming regime the spin relaxation is substantially modified, and the current-induced spin orientation is remarkably increased. Under short-pulsed photoexcitation at the bottom of conduction band the photoelectrons execute a periodic damped motion in the energy space with the period equal to the free flight time of an electron in the passive region. If the short optical pulse is circularly polarized so that the photocarriers are spin oriented, then the spin energy distribution is oscillating in time as well, which can be detected in the pump-probe time-resolved experiments. We show that the spin-orbit splitting of the conduction band becomes a source for additional spin oscillations, periodic or aperiodic depending on the value of electric field.