Theory of Weak Localization in Ferromagnetic (Ga,Mn)As

TL;DR

This paper investigates quantum interference effects in ferromagnetic (Ga,Mn)As semiconductors, revealing how exchange interactions transform weak antilocalization into weak localization, with implications for understanding low-temperature magnetoresistance.

Contribution

It introduces a model showing how exchange splitting causes a transition from WAL to WL in (Ga,Mn)As, clarifying experimental and theoretical interpretations.

Findings

Quantum interference corrections lead to negative magnetoresistance at Mn > 1%.

Exchange splitting converts valence band WAL into WL.

Highlights differences between (Ga,Mn)As and toy model systems.

Abstract

We study quantum interference corrections to the conductivity in (Ga,Mn)As ferromagnetic semiconductors using a model with disordered valence band holes coupled to localized Mn moments through a p-d kinetic-exchange interaction. We find that at Mn concentrations above 1% quantum interference corrections lead to negative magnetoresistance, i.e. to weak localization (WL) rather than weak antilocalization (WAL). Our work highlights key qualitative differences between (Ga,Mn)As and previously studied toy model systems, and pinpoints the mechanism by which exchange splitting in the ferromagnetic state converts valence band WAL into WL. We comment on recent experimental studies and theoretical analyses of low-temperature magnetoresistance in (Ga,Mn)As which have been variously interpreted as implying both WL and WAL and as requiring an impurity-band interpretation of transport in metallic (Ga,Mn)As.