Embedded Topological Semimetals

TL;DR

This paper explores how layered insulators can host embedded topological semimetals at defects, revealing new ways to identify Dirac semimetals experimentally through magnetic field responses.

Contribution

It demonstrates that crystal defects in layered insulators can host lower-dimensional topological semimetals, providing a novel perspective on defect-bound topological states.

Findings

Defects like stacking faults can host topological semimetals.

Embedded Dirac semimetals can be detected via Landau level spectroscopy.

Layered trivial insulators can contain topological semimetal states at defects.

Abstract

Topological semimetals, such as Dirac, Weyl, or line-node semimetals, are gapless states of matter characterized by their nodal band structures and surface states. In this work, we consider layered (topologically trivial) insulating systems in $D$ dimensions that are composed of coupled multi-layers of $d$-dimensional topological semimetals. Despite being nominal bulk insulators, we show that crystal defects having co-dimension $(D-d)$ can harbor robust lower dimensional topological semimetals embedded in a trivial insulating background. As an example we show that defect-bound topological semimetals can be localized on stacking faults and partial dislocations. Finally, we propose how an embedded topological Dirac semimetal can be identified in experiment by introducing a magnetic field and resolving the relativistic massless Dirac Landau level spectrum at low energies in an otherwise gapped system.