Topological crystalline insulator states in Pb(1-x)Sn(x)Se

TL;DR

This paper demonstrates that Pb(1-x)Sn(x)Se becomes a topological crystalline insulator at x=0.23 through temperature-dependent experiments, revealing a new class of topological insulators protected by crystalline symmetry.

Contribution

It provides experimental evidence of a topological crystalline insulator phase in Pb(1-x)Sn(x)Se, showing a temperature-driven phase transition, thus expanding the family of topological insulators.

Findings

Pb(1-x)Sn(x)Se is a topological crystalline insulator at x=0.23

Temperature induces a transition from trivial to topological phase

Experimental techniques include magnetotransport and photoelectron spectroscopy

Abstract

Topological insulators are a novel class of quantum materials in which time-reversal symmetry, relativistic (spin-orbit) effects and an inverted band structure result in electronic metallic states on the surfaces of bulk crystals. These helical states exhibit a Dirac-like energy dispersion across the bulk bandgap, and they are topologically protected. Recent theoretical proposals have suggested the existence of topological crystalline insulators, a novel class of topological insulators in which crystalline symmetry replaces the role of time-reversal symmetry in topological protection [1,2]. In this study, we show that the narrow-gap semiconductor Pb(1-x)Sn(x)Se is a topological crystalline insulator for x=0.23. Temperature-dependent magnetotransport measurements and angle-resolved photoelectron spectroscopy demonstrate that the material undergoes a temperature-driven topological phase transition from a trivial insulator to a topological crystalline insulator. These experimental findings add a new class to the family of topological insulators. We expect these results to be the beginning of both a considerable body of additional research on topological crystalline insulators as well as detailed studies of topological phase transitions.