Gate-tunable anomalous Hall effect in a 3D topological insulator/2D magnet van der Waals heterostructure

TL;DR

This paper demonstrates that mechanically stacked van der Waals heterostructures of a 3D topological insulator and a 2D magnet exhibit gate-tunable anomalous Hall effects, revealing control over topological surface states via magnetic interactions.

Contribution

It introduces a novel method of fabricating TI/magnet heterostructures with pristine interfaces and shows gate-tunable AHE linked to Berry curvature effects.

Findings

Gate-tunable AHE observed near the Dirac point.

Pristine interfaces achieved through mechanical stacking.

AHE linked to Berry curvature and exchange gap.

Abstract

We demonstrate advantages of samples made by mechanical stacking of exfoliated van der Waals materials for controlling the topological surface state of a 3-dimensional topological insulator (TI) via interaction with an adjacent magnet layer. We assemble bilayers with pristine interfaces using exfoliated flakes of the TI BiSbTeSe2 and the magnet Cr2Ge2Te6, thereby avoiding problems caused by interdiffusion that can affect interfaces made by top-down deposition methods. The samples exhibit an anomalous Hall effect (AHE) with abrupt hysteretic switching. For the first time in samples composed of a TI and a separate ferromagnetic layer, we demonstrate that the amplitude of the AHE can be tuned via gate voltage with a strong peak near the Dirac point. This is the signature expected for the AHE due to Berry curvature associated with an exchange gap induced by interaction between the topological surface state and an out-of-plane-oriented magnet.