Half-integer anomalous currents in 2D materials from a QFT viewpoint

TL;DR

This paper predicts a novel intrinsic half-integer quantum Hall effect in 2D materials caused by the 2D parity anomaly, independent of magnetic fields, with potential realization in disturbed honeycomb lattices.

Contribution

It introduces a new topological quantum Hall effect driven by the 2D parity anomaly, expanding understanding of quantum phenomena in Dirac/Weyl semi-metals.

Findings

Proposes a half-integer quantum Hall effect without magnetic field.

Links the effect to the 2D parity anomaly.

Suggests material setups for experimental observation.

Abstract

Charge carriers in Dirac/Weyl semi-metals exhibit a relativistic-like behavior. In this work we propose a novel type of intrinsic half-integer Quantum Hall effect in 2D materials, thereby also offering a topological protection mechanism for the current. Its existence is rooted in the 2D parity anomaly, without any need for a perpendicular magnetic field. We conjecture that it may occur in disturbed honeycomb lattices where both spin degeneracy and time reversal symmetry are broken. These configurations harbor two distinct gap-opening mechanisms that, when occurring simultaneously, drive slightly different gaps in each valley, causing a net anomalous conductivity when the chemical potential is tuned to be between the distinct gaps. Some examples of promising material setups that fulfill the prerequisites of our proposal are also listed to motivate looking for the effect at the numerical and experimental level.