Quantum Interference Controls the Electron Spin Dynamics in n-GaAs

TL;DR

This paper demonstrates that quantum interference effects, specifically weak localization, significantly influence electron spin relaxation in n-GaAs, revealing a new way to study quantum magneto-transport phenomena through optical spectroscopy.

Contribution

It shows that weak localization controls electron spin relaxation in semiconductors and can be observed via optical methods, linking quantum interference with spin dynamics.

Findings

Weak localization slows electron spin relaxation by nearly a factor of two.

Magnetic fields of about 1 T suppress weak localization effects.

Anomalous decrease of spin relaxation time T1 with magnetic field was observed.

Abstract

Manifestations of quantum interference effects in macroscopic objects are rare. Weak localization is one of the few examples of such effects showing up in the electron transport through solid state. Here we show that weak localization becomes prominent also in optical spectroscopy via detection of the electron spin dynamics. In particular, we find that weak localization controls the free electron spin relaxation in semiconductors at low temperatures and weak magnetic fields by slowing it down by almost a factor of two in $n$-doped GaAs in the metallic phase. The weak localization effect on the spin relaxation is suppressed by moderate magnetic fields of about 1 T, which destroy the interference of electron trajectories, and by increasing the temperature. The weak localization suppression causes an anomalous decrease of the longitudinal electron spin relaxation time $T_1$ with magnetic field, in stark contrast with well-known magnetic field induced increase in $T_1$. This is consistent with transport measurements which show the same variation of resistivity with magnetic field. Our discovery opens a vast playground to explore quantum magneto-transport effects optically in the spin dynamics.