Generalization of the Nested Wilson Loop Formalism in Topological Dirac Semimetals with Higher-order Fermi Arcs

TL;DR

This paper extends the nested Wilson loop formalism to analyze higher-order topological states in 2D and 3D nonsymmorphic Dirac semimetals, establishing a bulk-hinge correspondence via a generalized Berry phase.

Contribution

It introduces a generalized nested Berry phase as a bulk topological indicator for higher-order Fermi arcs in Dirac semimetals, advancing the understanding of higher-order topology.

Findings

gNBP predicts the presence of HOFAs in Dirac semimetals.

First-principles calculations confirm the correlation between gNBP changes and HOFAs termination.

The formalism applies to nonsymmorphic systems, broadening topological analysis tools.

Abstract

We generalize the nested Wilson loop formalism, which has been playing an important role in the study of topological quadrupole insulators, to two-dimensional (2D) and 3D nonsymmorphic materials with higher-order topology. In particular, certain 3D Dirac semimetals exhibit 1D higher-order Fermi arc (HOFA) states localizing on hinges where two surfaces meet and connecting the projection of the bulk Dirac points. We discover that the generalized nested Berry phase (gNBP) derived from this formalism is the bulk topological indicator determining the existence/absence of HOFAs, revealing a direct bulk-hinge correspondence in 3D Dirac semimetals. Finally, we study the Dirac semimetals NaCuSe and KMgBi based on first-principles calculations and explicitly show that the change in gNBP adjacent to the Dirac point corresponds to the termination of HOFAs at the projection of Dirac points on the hinge. Our findings not only improve the understanding of the bulk-hinge correspondence in topological Dirac semimetals but also provide a general formalism for studying the higher-order topology in nonsymmorphic systems.