Universal conductance fluctuations in epitaxial GaMnAs ferromagnets: structural and spin disorder

TL;DR

This study investigates quantum interference effects in epitaxial GaMnAs ferromagnets, revealing large phase coherence lengths and the influence of structural and spin disorder on conductance fluctuations.

Contribution

It provides new insights into the quantum interference phenomena and decoherence mechanisms in GaMnAs, highlighting the roles of structural and spin disorder.

Findings

Large phase coherence length in GaMnAs ferromagnets.

Quantum interferences dominated by structural disorder at high fields.

Persistence of phase coherence down to zero field despite magnons.

Abstract

Mesoscopic transport measurements reveal a large effective phase coherence length in epitaxial GaMnAs ferromagnets, contrary to usual 3d-metal ferromagnets. Universal conductance fluctuations of single nanowires are compared for epilayers with a tailored anisotropy. At large magnetic fields, quantum interferences are due to structural disorder only, and an unusual behavior related to hole-induced ferromagnetism is evidenced, for both quantum interferences and decoherence. At small fields, phase coherence is shown to persist down to zero field, even in presence of magnons, and an additional spin disorder contribution to quantum interferences is observed under domain walls nucleation.