Weak localization in GaMnAs: evidence of impurity band transport

TL;DR

This paper presents evidence of weak localization in GaMnAs, supporting impurity band transport over valence band conduction, through low-temperature magnetoresistance measurements revealing quantum interference effects.

Contribution

It provides experimental evidence of weak localization in GaMnAs, indicating impurity band transport, which clarifies the conduction mechanism in this ferromagnetic semiconductor.

Findings

Negative magnetoresistance observed at low temperatures and fields

Weak localization attributed to impurity band transport

Detection of Altshuler-Aronov electron-electron interactions

Abstract

We report the observation of negative magnetoresistance in the ferromagnetic semiconductor GaMnAs at low temperatures ($T<3$ K) and low magnetic fields ($0< B <20$ mT). We attribute this effect to weak localization. Observation of weak localization provides a strong evidence of impurity band transport in these materials, since for valence band transport one expects either weak anti-localization due to strong spin-orbit interactions or total suppression of interference by intrinsic magnetization. In addition to the weak localization, we observe Altshuler-Aronov electron-electron interactions effect in this material.