Vertical transverse transport induced by hidden in-plane Berry curvature in two dimensions

TL;DR

This paper introduces a modified in-plane Berry curvature in 2D materials to explain vertical transverse transport phenomena, supported by first-principles calculations on specific monolayers, revealing new quantum transport effects.

Contribution

It proposes a new formulation of Berry curvature with in-plane components to explain out-of-plane transport in 2D systems, expanding understanding of quantum phenomena.

Findings

Large in-plane BC in GdAg2 monolayer

Large BC dipole in BiAg2 monolayer

Significant vertical Hall effects in 2D materials

Abstract

The discovery of Berry curvature (BC) has spurred a tremendous surge of research into various quantum phenomena such as the anomalous transport of electrons and the topological phases of matter. In two-dimensional crystalline systems, the conventional definition of the BC lacks the in-plane components and thus it cannot explain the transverse transport along the plane-normal direction. Here, we modify the BC to newly provide in-plane components in two dimensions, giving rise to the vertical Hall effects that describe out-of-plane transports in response to in-plane perturbations and their Onsager reciprocity. Our first-principles calculations show that a large in-plane BC can appear even in an atomic-thick GdAg2 monolayer, and a hexagonal BiAg2 monolayer can host a large BC dipole known to vanish in the conventional BC. The quantum transports driven by the hitherto-hidden BC will become more significant in recently emerging two-dimensional platforms, including van der Waals heterostructures.