Theory of spin precession monitored by laser pulse

TL;DR

This paper predicts how circularly polarized laser pulses can induce and control spin precession in impurity levels within semiconductors, enabling ultrafast spin manipulation through many-body interaction effects.

Contribution

It introduces a theoretical framework for laser-induced spin splitting and precession in impurities, extending understanding of spin dynamics under optical control.

Findings

Laser irradiation causes spin splitting of impurity levels.

Induced spin precession lasts as long as the laser pulse.

The effect is related to many-body exchange interactions.

Abstract

We first predict the splitting of a spin degenerate impurity level when this impurity is irradiated by a circularly polarized laser beam tuned in the transparency region of a semiconductor. This splitting, which comes from different exchange processes between the impurity electron and the virtual pairs coupled to the pump beam, induces a spin precession around the laser beam axis, which lasts as long as the pump pulse. It can thus be used for ultrafast spin manipulation. This effect, which has similarities with the exciton optical Stark effect we studied long ago, is here derived using the concepts we developed very recently to treat many-body interactions between composite excitons and which make the physics of this type of effects quite transparent. They, in particular, allow to easily extend this work to other experimental situations in which a spin rotates under laser irradiation.