Spinor-dominated magnetoresistance in β-Ag2Se

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 β-Ag2Se, 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 β-Ag2Se, 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. A defining characteristic of non-trivial topological materials is the bulk-boundary correspondence, and the majority of research activities has tended to centre around the surface states. Here, the authors conduct electrical transport measurements on β-Ag2Se observing anomalies in the magnetoresistance measurements, which they contend has a direct connection to the non-trivial topological nature of β-Ag2Se.