Electrically switchable giant Berry curvature dipole in silicene, germanene and stanene

TL;DR

This paper demonstrates that applying an electric field and strain to silicene, germanene, and stanene induces a giant, electrically switchable Berry curvature dipole, enabling nonlinear Hall effects in these elemental 2D materials.

Contribution

It reveals how electric fields and strain can induce a giant, switchable Berry curvature dipole in buckled honeycomb lattices, a novel control mechanism for nonlinear Hall effects.

Findings

Giant Berry curvature dipole occurs at the band gap closing point.

Electric field breaks inversion symmetry, enabling nonlinear Hall effects.

Strain induces asymmetrical Berry curvature distribution.

Abstract

The anomalous Hall effect in time-reversal symmetry broken systems is underpinned by the concept of Berry curvature in band theory. However, recent experiments reveal that the nonlinear Hall effect can be observed in non-magnetic systems without applying an external magnetic field. The emergence of nonlinear Hall effect under time-reversal symmetric conditions can be explained in terms of non-vanishing Berry curvature dipole arising from inversion symmetry breaking. In this work, we availed realistic tight-binding models, first-principles calculations, and symmetry analyses to explore the combined effect of transverse electric field and strain, which leads to a giant Berry curvature dipole in the elemental buckled honeycomb lattices -- silicene, germanene, and stanene. The external electric field breaks the inversion symmetry of these systems, while strain helps to attain an asymmetrical distribution of Berry curvature of a single valley. Furthermore, the topology of the electronic wavefunction switches from the band inverted quantum spin Hall state to normal insulating one at the gapless point. This band gap closing at the critical electric field strength is accompanied by an enhanced Berry curvature and concomitantly a giant Berry curvature dipole at the Fermi level. Our results predict the occurrence of an electrically switchable nonlinear electrical and thermal Hall effect in a new class of elemental systems that can be experimentally verified.