Topological Crystalline Magnets: Symmetry-Protected Topological Phases of Fermions

TL;DR

This paper introduces a new class of topological crystalline insulators called topological crystalline magnets, protected by combined symmetries, exhibiting robust edge states and unique symmetry properties, advancing understanding of symmetry-protected topological phases.

Contribution

It proposes a novel class of interaction-enabled topological phases called topological crystalline magnets, characterized by symmetry protection and robustness against certain perturbations.

Findings

Topological crystalline magnets cannot be connected to Slater insulators.

Edge states are robust against electron coupling.

Anisotropic magnetic response can serve as an experimental signature.

Abstract

We introduce a novel class of interaction-enabled topological crystalline insulators in two- and three-dimensional electronic systems, which we call "topological crystalline magnet." It is protected by the product of the time-reversal symmetry $\mathcal{T}$ and a mirror symmetry or a rotation symmetry $\mathcal{R}$. A topological crystalline magnet exhibits two intriguing features: (i) it cannot be adiabatically connected to any Slater insulator and (ii) the edge state is robust against coupling electrons to the edge. These features are protected by the anomalous symmetry transformation property $(\mathcal{R} \mathcal{T})^2=-1$ of the edge state. An anisotropic response to the external magnetic field can be an experimental signature.