Two-dimensional higher-order Weyl semimetals

TL;DR

This paper proposes a theoretical method to realize two-dimensional higher-order Weyl semimetals using a trilayer topological insulator and a d-wave altermagnet, revealing unique edge and corner states.

Contribution

It introduces a novel scheme combining topological insulators and altermagnets to achieve higher-order Weyl semimetals with topological corner states.

Findings

Weyl points are located at four high-symmetry points in the Brillouin zone.

Gaps open in helical edge states while Weyl points are preserved.

Topological phase diagram characterizes the system's phases.

Abstract

We propose a theoretical scheme to realize two-dimensional higher-order Weyl semimetals using a trilayer topological insulator film coupled with a d-wave altermagnet. Our results show that the trilayer topological insulator exhibits two-dimensional Weyl semimetal characteristics with helical edge states. Notably, the Weyl points are located at four high-symmetry points in the Brillouin zone, and the topology of symmetric subspaces governs the formation of these Weyl points and edge states. Upon introducing a d-wave altermagnet oriented along the z-direction, gaps open in the helical edge states while preserving two Weyl points, leading to the realization of two-dimensional higher-order Weyl semimetals hosting topological corner states. The nonzero winding number in the subspace along the high-symmetry line serves as a topological invariant characterizing these corner states, and the other subspace Hamiltonian confirms the existence of the Weyl points. Finally, a topological phase diagram provides a complete topological description of the system.