Topological Quantum Spin Hall Semimetals with Light

TL;DR

This paper proposes a new class of topological quantum spin Hall semimetals that can be detected via circularly polarized light, combining spin-orbit effects and topological band structures on honeycomb lattices.

Contribution

It introduces a novel topological semimetal with a measurable Z2 invariant and suggests methods to engineer such systems using charge or spin density waves and Zeeman effects.

Findings

Presence of topologically protected helical edge currents

Measurable Z2 invariant via circularly polarized light

Realization through honeycomb lattice band structures

Abstract

We introduce a quantum spin Hall semimetal or Fermi liquid characterized with a Z2 topological invariant, measurable through circularly polarized light. We propose its engineering through two topological metallic band structures in crystals on the honeycomb lattice, with spin-orbit interaction, realizable through the interplay of a charge or spin density wave substrate and Zeeman effects, in between a quantum spin Hall and a quantum anomalous Hall insulator. These systems show topologically protected helical edge or photo-induced currents.