A pressure-induced topological phase with large Berry curvature in Pb$_{1-x}$Sn$_x$Te

TL;DR

This study demonstrates the existence of a pressure-induced topological metallic phase in Pb$_{1-x}$Sn$_x$Te, characterized by large Berry curvature and unique transport phenomena, confirmed through experimental and theoretical approaches.

Contribution

It provides experimental evidence for a topological metallic phase with Weyl nodes in Pb$_{1-x}$Sn$_x$Te induced by pressure, expanding understanding of topological phase transitions.

Findings

Observation of a pressure-tuned topological metallic phase

Detection of large Berry curvature affecting Hall effect

Giant negative magnetoresistance in the insulating regime

Abstract

The picture of how a gap closes in a semiconductor has been radically transformed by topological concepts. Instead of the gap closing and immediately re-opening, topological arguments predict that, in the absence of inversion symmetry, a metallic phase protected by Weyl nodes persists over a finite interval of the tuning parameter (e.g. pressure $P$) . The gap re-appears when the Weyl nodes mutually annihilate. We report evidence that Pb$_{1-x}$Sn$_x$Te exhibits this topological metallic phase. Using pressure to tune the gap, we have tracked the nucleation of a Fermi surface droplet that rapidly grows in volume with $P$. In the metallic state we observe a large Berry curvature which dominates the Hall effect. Moreover, a giant negative magnetoresistance is observed in the insulating side of phase boundaries, in accord with \emph{ab initio} calculations. The results confirm the existence of a topological metallic phase over a finite pressure interval.