Direct probing of band-structure Berry phase in diluted magnetic semiconductors

TL;DR

This paper provides experimental evidence of the Berry phase in the band structure of a ferromagnetic semiconductor, observed through unique magnetoconductance patterns in nanowires, revealing a new way to probe band topology.

Contribution

It demonstrates a direct experimental method to detect the band-structure Berry phase via mesoscopic transport measurements in (Ga,Mn)(As,P) nanowires, linking magnetization rotation to topological effects.

Findings

Distinct magnetoconductance patterns linked to Berry phase

Berry phase signatures appear during coherent magnetization rotation

Method enables controlled probing of band structure topology

Abstract

We report on experimental evidence of the Berry phase accumulated by the charge carrier wave function in single-domain nanowires made from a (Ga,Mn)(As,P) diluted ferromagnetic semiconductor layer. Its signature on the mesoscopic transport measurements is revealed as unusual patterns in the magnetoconductance, that are clearly distinguished from the universal conductance fluctuations. We show that these patterns appear in a magnetic field region where the magnetization rotates coherently and are related to a change in the band-structure Berry phase as the magnetization direction changes. They should be thus considered as a band structure Berry phase fingerprint of the effective magnetic monopoles in the momentum space. We argue that this is an efficient method to vary the band structure in a controlled way and to probe it directly. Hence, (Ga,Mn)As appears to be a very interesting test bench for new concepts based on this geometrical phase.