2019/01/31 by Y. Gao, Y. Qin, S. Kaushik +13
Materials Science · Physics and Astronomy · #Anisotropy #Circular polarization #Fermion #Magnetic properties of thin films #Metamaterials and Metasurfaces Applications #Photoexcitation #Photon #Semimetal #Terahertz radiation #Topological Materials and Phenomena #Weyl semimetal #cond-mat.mtrl-sci #cond-mat.other #physics.optics
paper · pdf · doi:10.1038/s41467-020-14463-1
published as Nat. Commun. 11, 720 (2020)
arxiv created 2019/06/19 · openalex created_date 2019/06/27 · openalex publication_date 2020/02/05 · arxiv updated 2020/02/07 · openalex updated_date 2026/08/06
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.