專題演講

2021/01/14(Thu)     10:30 -12:00    五樓第一會議室5th Floor(1st meeting room)

Title

New Hall effect goes nonlinear

Speaker

Dr. Jhih-Shih You

Department of Physics, National Taiwan Normal University

Abstract

In this talk I will introduce our recent study of the nonlinear Hall effect in materials with time-reversal symmetry. In the absence of magnetic field, the Hall effect in the linear response regime vanishes due to time-reversal symmetry. However, a transverse charge current can still occur in second-order response to an external electric field, as a result of the Berry curvature dipole (BCD) in momentum space. Candidate 2D materials to observe this effect are two-dimensional transition-metal dichalcogenides (TMDCs). The application of strain and electrical displacement field can systematically control the BCD in TMDCs. We also demonstrate that 3D giant-Rashba material bismuth tellurium iodine (BiTeI) exhibits a pressure-driven phase transition between topological and trivial insulators, which is accompanied by a giant enhancement of the BCD which can be probed in transport and optoelectronic experiments. While there has been much effort to understand nonlinear transport due to a BCD in bulk, we further find that the topological materials with a conducting surface, like Weyl Fermi arcs, could host a surface BCD. The bulk and surface BCDs are relevant for the understanding of quantum phenomena such as nonlinear anomalous Nernst effect and the circular photogalvanic effect.

Ref:
1. J.-S. You, S. Fang, S.-Y. Xu, E. Kaxiras and T. Low, Phys. Rev. B 98, 121109 (2018).
2. J. I. Facio, D. Efremov, K. Koepernik, J.-S. You, I. Sodemann, and J. van den Brink, Phys. Rev. Lett. 121, 246403 (2018).
3. J. Quereda, TS Ghiasi, J.-S. You, J. van den Brink, BJ van Wees, CH van der Wal, Nature communications 9, 3346 (2018).
4. X.-Q. Yu, Z.-G. Zhu, J.-S. You, T. Low, G. Su, Phys. Rev. B 99, 201410 (2019).
5. D. Wawrzik, J.-S. You, J. I. Facio, J. van den Brink, I. Sodemann, arXiv:2010.10537. (Speaker Instroduction)