The topological-crystalline-insulator (Pb,Sn)Te - surface states and their spin-polarization

TL;DR

This theoretical study explores the surface states and spin textures of the topological-crystalline-insulator Pb0.4Sn0.6Te across different crystal surfaces, revealing protected Dirac cones and valley interactions.

Contribution

It extends understanding of topological surface states in Pb0.4Sn0.6Te by analyzing multiple crystal surfaces and their topological protections using a tight-binding model.

Findings

(111) surface hosts four Dirac cones with topological protection.

(110) surface shows energy gaps due to valley interactions.

All surfaces exhibit chiral spin textures.

Abstract

Using a tight-binding approach we study theoretically the nature of surface states in Pb0.4Sn0.6Te - the newly discovered topological-crystalline-insulator. Apart from the studied before (001) surface states, two other surface families, {011} and {111}, in which the mirror symmetry of the crystal's rock-salt structure plays the same role in topological protection, are considered. Our calculations show that while in (111) surface states of (Pb,Sn)Te four single topologically protected Dirac-cones should appear, for the (110) surface states the protection is lifted for two L points. In this case, instead of the Dirac points energy gaps occur in the surface states, due to the interaction between the two L valleys. In all studied cases a chiral spin texture is obtained.