Nonlinear Hall Effects in Weyl Semimetal Thin Films*

Weyl semimetals (WSMs) are a gapless topological phase that have attracted great attention in the past decade or so. The study of the bulk properties of WSMs has led to fruitful discoveries such as negative magnetoresistance, planar Hall effect, etc. More recently, there have been intense efforts in investigations beyond the linear transport regime, leading to proposals of nonlinear Hall effect of different origins, such as the Berry curvature dipole [1] and the chiral anomaly [2]. On the other hand, due to its unique band topology, the Fermi arc states emerge on the surfaces of a WSM, which are distinct from the surface states of gapped systems such as topological insulators. In this work, we will focus on the nonlinear Hall effects in WSM thin films in which the surface states are expected to play a more important role in charge transport due to large surface-to-volume ratio. In particular, we will employ a tight-binding model of a WSM and demonstrate how the Fermi arc states impact the chiral-anomaly-induced nonlinear Hall response under parallel electric and magnetic fields. In addition, we will also discuss how diffusion, which becomes prominent in the thin film geometry, can lead to modifications in nonlinear Hall effects of WSMs.

References:

1. I. Sodemann and L. Fu, Phys. Rev. Lett. 115, 216806 (2015)

2. R.-H. Li, O. G. Heinonen, A. A. Burkov, and S. S.-L. Zhang, Phys. Rev. B 103, 045105 (2021).