Observation of Temperature Independent Anomalous Hall Effect in Thin Bismuth from Near Absolute Zero to 300 K Temperature

TL;DR

This study reports a temperature-independent anomalous Hall effect in thin pure bismuth from near absolute zero to room temperature, suggesting an intrinsic origin possibly related to surface Berry curvature effects.

Contribution

The paper presents the first observation of a temperature-independent AHE in pure bismuth, indicating an intrinsic mechanism unrelated to magnetic impurities or magnetoresistance.

Findings

AHE persists from 15 mK to 300 K in pure bismuth.

No magnetoresistance observed between ±30 T magnetic fields.

Intrinsic AHE possibly caused by surface Berry curvature breaking inversion symmetry.

Abstract

We report our discovery of a temperature independent anomalous Hall effect (AHE) from 15 mK to 300 K temperature occurring in a 68 nm thick transport device made out of pure bismuth. This surprising behaviour is accompanied with an expected temperature dependent longitudinal resistance consistent with semi-metallic bismuth, however it surprisingly showed no hint of a magnetoresistance for magnetic fields between $\pm30$ T. Even though bismuth is a diamagnetic material which {\it a priori} does not break time-reversal symmetry (TRS), our analysis of the reconstructed conductivities points towards the AHE to be of the intrinsic type, which does not emanate from magnetic impurities. Finally, as pure bismuth has been shown numerically to host a Berry curvature at its surface which breaks inversion symmetry, we propose it as a possible explanation for the temperature independent AHE observed here.