Topological phase diagram and saddle point singularity in a tunable topological crystalline insulator

TL;DR

This study explores how the surface electronic structure and topological phases of Pb1-xSnxSe, a tunable topological crystalline insulator, change with composition, temperature, and structure, revealing a rich phase diagram and unique topological features.

Contribution

It provides the first systematic analysis of the tunability of surface states and phase transitions in Pb1-xSnxSe, highlighting distinct mechanisms compared to other topological insulators.

Findings

Surface states' response to circularly polarized light demonstrated.

Material parameters can tune the system between trivial and topological phases.

Identified the electronic groundstate condition for saddle point singularity.

Abstract

We report the evolution of the surface electronic structure and surface material properties of a topological crystalline insulator (TCI) Pb1-xSnxSe as a function of various material parameters including composition x, temperature T and crystal structure. Our spectroscopic data demonstrate the electronic groundstate condition for the saddle point singularity, the tunability of surface chemical potential, and the surface states' response to circularly polarized light. Our results show that each material parameter can tune the system between trivial and topological phase in a distinct way unlike as seen in Bi2Se3 and related compounds, leading to a rich and unique topological phase diagram. Our systematic studies of the TCI Pb1-xSnxSe are valuable materials guide to realize new topological phenomena.