Chiral terahertz wave emission from the Weyl semimetal TaAs

Y Gao; S Kaushik; E J Philip; Z Li; Y Qin; Y P Liu; W L Zhang; Y L Su; X Chen; H Weng; D E Kharzeev; M K Liu; J Qi

doi:10.1038/s41467-020-14463-1

Chiral terahertz wave emission from the Weyl semimetal TaAs

Nat Commun. 2020 Feb 5;11(1):720. doi: 10.1038/s41467-020-14463-1.

Authors

Y Gao¹, S Kaushik², E J Philip², Z Li^{3

4}, Y Qin^{1

5}, Y P Liu⁶, W L Zhang¹, Y L Su¹, X Chen², H Weng^{4

7}, D E Kharzeev^{8

9

10}, M K Liu¹¹, J Qi¹²

Affiliations

¹ State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu, 611731, China.
² Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY, 11794, USA.
³ State Key Laboratory for Artificial Microstructure and Mesoscopic Physics, Beijing Key Laboratory of Quantum Devices, Peking University, Beijing, 100871, China.
⁴ Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China.
⁵ Institute of Electronic and Information Engineering, University of Electronic Science and Technology of China, Dongguan, 523808, China.
⁶ Institute of Modern Physics, Fudan University, Shanghai, 200433, China.
⁷ Songshan Lake Materials Laboratory, Dongguan, 523808, China.
⁸ Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY, 11794, USA. dmitri.kharzeev@stonybrook.edu.
⁹ Department of Physics, Brookhaven National Laboratory, Upton, NY, 11973-5000, USA. dmitri.kharzeev@stonybrook.edu.
¹⁰ RIKEN-BNL Research Center, Brookhaven National Laboratory, Upton, NY, 11973-5000, USA. dmitri.kharzeev@stonybrook.edu.
¹¹ Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY, 11794, USA. mengkun.liu@stonybrook.edu.
¹² State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu, 611731, China. jbqi@uestc.edu.cn.

Abstract

Weyl semimetals host chiral fermions with distinct chiralities and spin textures. Optical excitations involving those chiral fermions can induce exotic carrier responses, and in turn lead to novel optical phenomena. Here, we discover strong coherent terahertz emission from Weyl semimetal TaAs, which is demonstrated as a unique broadband source of the chiral terahertz wave. The polarization control of the THz emission is achieved by tuning photoexcitation of ultrafast photocurrents via the photogalvanic effect. In the near-infrared regime, the photon-energy dependent nonthermal current due to the predominant circular photogalvanic effect can be attributed to the radical change of the band velocities when the chiral Weyl fermions are excited during selective optical transitions between the tilted anisotropic Weyl cones and the massive bulk bands. Our findings provide a design concept for creating chiral photon sources using quantum materials and open up new opportunities for developing ultrafast opto-electronics using Weyl physics.