Colloquium: Orbital and Layer-Coherence Origin of Intrinsic Planar Hall Effect

ABSTRACT

The intrinsic planar Hall effect (IPHE) has attracted intensive interest inspired by recent experiments. Existing theories rely mainly on a spin origin, which requires spin-orbit coupling to take effect. In this talk I will introduce two of our recent theories on the origin of IPHE without replying on spin-orbit coupling. First, I will talk about an orbital mechanism in 3D materials [1], which enables sizable IPHE to occur in systems with weak spin-orbit coupling and dominates in topological metals even with strong spin-orbit couping. Second, I will introduce in quasi-2D materials a new origin of the effect - as an intrinsic property of layer coherent electrons - that allows its presence even in bilayer and trilayer atomically thin limit [2]. This layer-coherence induced IPHE features rich tunability and even stronger magnitude than those induced by topological nodal structures in bulk materials. The layer mechanism also provides a new route towards quantized Hall response upon a topological phase transition induced by in-plane magnetic field. These results unveil the unexplored potential of quantum layertronics and moiré flat band for planar Hall transport.

[1] H. Wang, Y.X. Huang, H. Liu, X. Feng, .J Zhu, W. Wu, C. Xiao*, S.A. Yang, Orbital Origin of the Intrinsic Planar Hall Effect, Physical Review Letters 132, 056301 (2024); [2] H. Zheng, D. Zhai, C. Xiao*, W. Yao*, Layer Coherence Origin of Intrinsic Planar Hall Effect in 2D Limit, arXiv:2402.17166.

BIOGRAPHY

Prof. Cong Xiao obtained his PhD in theretical physics from Peking University in 2016. After that, he worked as a postdoc in the University of Texas at Austin with Prof. Qian Niu and as a research assistant professor in the University of Hong Kong with Prof. Wang Yao. He joined the institute of applied physics and materials engineering in the University of Macau on August 2023. His research interest is in exotic transport and response properties in condensed matter physics, especially those related to Berry phase. His recent works focus mainly on uncovering novel nonlinear transport and nonlinear spintronics effects. In particular, he proposed the detection scheme of Neel vector switching by intrinsic nonlinear Hall effect, the orbital and layer origin of intrinsic planar Hall effect, the intrinsic nonlinear planar Hall effect, and the nonlinear spin-orbit torque.