Half-Quantized Hall Effect at the Parity-Invariant Fermi Surface

TL;DR

This paper reports the discovery of a half-quantized Hall conductance associated with a stable, gapless Dirac cone in a magnetically-doped topological insulator, demonstrating a novel topological phase with parity symmetry.

Contribution

It provides the first experimental realization of a half-quantized Hall effect linked to a parity-invariant Dirac surface state in a topological insulator heterostructure.

Findings

Observation of a half-quantized Hall conductance in experiments

Identification of a stable, gapless Dirac cone protected by parity symmetry

Connection of the results to a topological phase with a half-integer invariant

Abstract

Condensed matter realization of a single Dirac cone of fermions in two dimensions is a long-standing issue. Here we report the discovery of a single gapless Dirac cone of half-quantized Hall conductance in a magnetically-doped topological insulator heterostructure. It demonstrates that the Hall conductance is half-quantized in the unit e^{2}/h when the parity symmetry is invariant near the Fermi surface. The gapless Dirac point is stable and protected by the local parity symmetry and the topologically nontrivial band structure of the topological insulator. The one-half Hall conductance observed in a recent experiment [Mogi et al, Nat. Phys. 18, 390 (2022)] is attributed to the existence of the gapless Dirac cone. The results suggest a condensed matter realization of a topological phase with a one-half topological invariant.