Topological semimetals in the SnTe material class: Nodal lines and Weyl points

TL;DR

This paper predicts that certain low-temperature phases of SnTe and related compounds can host topological semimetal phases, including Weyl points and nodal lines, due to symmetry-breaking structural distortions.

Contribution

It introduces a theoretical framework showing how structural symmetry reduction in SnTe leads to topological semimetal phases, providing explicit models and expressions for these features.

Findings

Weyl points and nodal lines emerge in low-temperature SnTe.

Structural distortions induce topological semimetal phases.

Potential realization in ferroelectric phases of SnTe and GeTe.

Abstract

We theoretically show that IV-VI semiconducting compounds with low-temperature rhombohedral crystal structure represent a new potential platform for topological semimetals. By means of minimal $\mathbf{k}\cdot\mathbf{p}$ models we find that the two-step structural symmetry reduction of the high-temperature rocksalt crystal structure, comprising a rhombohedral distortion along the [111] direction followed by a relative shift of the cation and anion sublattices, gives rise to topologically protected Weyl semimetal and nodal line semimetal phases. We derive general expressions for the nodal features and apply our results to SnTe showing explicitly how Weyl points and nodal lines emerge in this system. Experimentally, the topological semimetals could potentially be realized in the low-temperature ferroelectric phase of SnTe, GeTe and related alloys.