Time-reversal invariant realization of the Weyl semimetal phase

TL;DR

This paper presents a time-reversal invariant Weyl semimetal phase realized in HgTe/CdTe multilayers, characterized by robust Weyl points, surface states, and anisotropic conductivity, bridging normal and topological insulator phases.

Contribution

It introduces a new realization of Weyl semimetals that preserves time-reversal symmetry, using realistic multilayer structures and models.

Findings

Existence of Weyl semimetal phase between insulator phases

Presence of topological surface states in the phase

Anisotropic conductivity behavior

Abstract

We propose a realization of the Weyl semimetal phase that is invariant under time reversal and occurs due to broken inversion symmetry. We consider both a simple superlattice model and a more realistic tight-binding model describing an experimentally reasonable HgTe/CdTe multilayer structure. The two models have the same underlying symmetry, therefore their low-energy features are equivalent. We find a Weyl semimetal phase between the normal insulator and the topological insulator phases that exists for a finite range of the system parameters and exhibits a finite number of Weyl points with robust band touching at the Fermi level. This phase is experimentally characterized by a strong conductivity anisotropy and topological surface states. The principal conductivities change in a complementary fashion as the system parameters are varied, and the surface states only exist in a region of momentum space that is determined by the positions of the Weyl points.