Spinor-dominated magnetoresistance driven by the topological phase transition in $\beta $-Ag$_2$Se

TL;DR

This paper reports the discovery of spinor-dominated magnetoresistance anomalies in the topological insulator $eta$-Ag$_2$Se$, driven by a magnetic-field-induced topological phase transition affecting bulk states.

Contribution

It reveals a new type of magnetoresistance controlled by wave-function spinors during a topological phase transition in a bulk topological insulator.

Findings

Observation of magnetoresistance anomalies caused by spinor orthogonality.

Backscattering is forbidden during the topological phase transition.

Potential device applications based on spinor-dominated magnetoresistance.

Abstract

A topological insulator is a quantum material which possesses conducting surfaces and an insulating bulk. Despite extensive researches on the properties of Dirac surface states, the characteristics of bulk states have remained largely unexplored. Here we report the observation of spinor-dominated magnetoresistance anomalies in the topological insulator $\beta $-Ag$_2$Se, induced by a magnetic-field-driven band topological phase transition. These anomalies are caused by intrinsic orthogonality in the wave-function spinors of the last Landau bands of the bulk states, in which backscattering is strictly forbidden during a band topological phase transition. This new type of longitudinal magnetoresistance, purely controlled by the wave-function spinors of the last Landau bands, highlights a unique signature of electrical transport around the band topological phase transition. With further reducing the quantum limit and gap size in $\beta $-Ag$_2$Se, our results may also suggest possible device applications based on this spinor-dominated mechanism and signify a rare case where topology enters the realm of magnetoresistance control.