Prediction of Topological Crystalline Insulator and Topological Phase Transitions in Two-dimensional PbTe Films

TL;DR

This study uses ab initio calculations to predict that 2D PbTe films are intrinsic topological crystalline insulators with large band gaps, capable of room-temperature quantum device applications, and explores phase transitions under strain.

Contribution

It is the first to identify 2D PbTe films as intrinsic TCIs with sizable gaps and controllable topological phases via strain, expanding the understanding of 2D topological materials.

Findings

Monolayer and trilayer PbTe are intrinsic 2D TCIs with 0.27 eV band gap.

Strain induces semimetal-TCI-normal insulator transitions.

TCI phase persists on NaI substrate, enabling device integration.

Abstract

Topological phases, especially topological crystalline insulators (TCIs), have been intensively explored observed experimentally in three-dimensional (3D) materials. However, the two-dimensional (2D) films are explored much less than 3D TCI, and even 2D topological insulators. Based on ab initio calculations, here we investigate the electronic and topological properties of 2D PbTe(001) few-layers. The monolayer and trilayer PbTe are both intrinsic 2D TCIs with a large band gap reaching 0.27 eV, indicating a high possibility for room-temperature observation of quantized conductance. The origin of TCI phase can be attributed to the p band inversion,which is determined by the competitions of orbital hybridization and quantum confinement. We also observe a semimetal-TCI-normal insulator transition under biaxial strains, whereas a uniaxial strains lead to Z2 nontrivial states. Especially, the TCI phase of PbTe monolayer remains when epitaxial grow on NaI semiconductor substrate. Our findings on the controllable quantum states with sizable band gaps present an ideal platform for realizing future topological quantum devices with ultralow dissipation.