A microscopic approach to spin dynamics: about the meaning of spin relaxation times

TL;DR

This paper develops a microscopic theoretical framework for understanding spin relaxation times in semiconductor systems, linking optical Bloch equations to spin dynamics and including carrier-phonon interactions.

Contribution

It extends optical Bloch equations to derive microscopic expressions for spin relaxation times in a 6-level semiconductor system, accounting for carrier-phonon interactions.

Findings

Derived microscopic expressions for T_1 and T_2 relaxation times.

Connected theoretical results with experimental measurements.

Included carrier-phonon scattering effects on spin dynamics.

Abstract

We present an approach to spin dynamics by extending the optical Bloch equations for the driven two-level system to derive microscopic expressions for the transverse and longitudinal spin relaxation times. This is done for the 6-level system of electron and hole subband states in a semiconductor or a semiconductor quantum structure to account for the degrees-of-freedom of the carrier spin and the polarization of the exciting light and includes the scattering between carriers and lattice vibrations on a microscopic level. For the subsystem of the spin-split electron subbands we treat the electron-phonon interaction in second order and derive a set of equations of motion for the 2x2 spin-density matrix which describes the electron spin dynamics and contains microscopic expressions for the longitudinal (T_1) and the transverse (T_2) spin relaxation times. Their meaning will be discussed in relation to experimental investigations of these quantities.