Time-reversal breaking topological phase without Hall electric current in a two-dimensional Dirac semimetal protected by nonsymmorphic symmetry

TL;DR

This paper explores a novel topological phase in a 2D Dirac semimetal that breaks time-reversal symmetry but does not produce Hall current, protected by nonsymmorphic symmetry, revealing unconventional edge states.

Contribution

It demonstrates the existence of an unconventional topological phase with helical edge modes without Hall current in a nonsymmorphic symmetry-protected 2D Dirac semimetal.

Findings

Identification of a new topological phase with helical edge modes

Demonstration of phase stability under nonsymmorphic symmetry preservation

Absence of Hall current despite topological edge states

Abstract

We investigate the topological phase derived by time-reversal breaking fields in a nonsymmorphic symmetry-protected two-dimensional Dirac semimetal. When the nonsymmorphic symmetry is preserved even in the presence of the field, the two-dimensional electronic states change into two distinct topological phases with the insulating gap. One phase is well-known as quantum Hall states with chiral edge modes accompanying the Hall current, but the other one is an unconventional topological phase with helical edge modes in the absence of time-reversal symmetry.