Elbert E. M. Chia
In this talk I will show terahertz (THz) emission data on a few topological materials. In the ferromagnet-semiconductor Co/MoS2 heterostructure, by making use of the strongly out-of-equilibrium character of the injected spins, we demonstrate a highly- efficient spin injection from a ferromagnet into a semiconductor, thus overcoming the crippling problem of impedance mismatch. Astonishingly, we measure a giant spin current that is orders of magnitude larger than typical injected spin current densities using currently available techniques [1]. In thin polycrystalline films of the centrosymmetric Dirac semimetal PtSe2, we observe a giant and highly tunable THz emission that is rapidly turned on at oblique incidence. Strikingly, we find the THz emission to be locked to both the in-plane photon momentum and polarization state of the incident pump beam, where the THz sign and amplitude are fully controlled by the incident pump polarization, helicity and photon momentum. Moreover, the emitted THz efficiency is two orders of magnitude larger than that of the standard THz- generating nonlinear crystal ZnTe, and approaches that of the record-setting topological material TaAs. Our work demonstrates how photon drag activates a rich and pronounced directional optical linearity that are available even in centrosymmetric and polycrystalline Dirac materials [2].
References
(2019).
Liang Cheng, Xinbo Wang, Weifeng Yang, Jianwei Chai, Ming Yang, Mengji Chen, Yang Wu, Xiaoxuan Chen, Dongzhi Chi, Kuan Eng Johnson Goh, Jian-Xin Zhu, Handong Sun, Shijie Wang, Justin C. W. Song, Marco Battiato, Hyunsoo Yang, and Elbert E. M. Chia, Nature Physics, DOI:10.1038/s41567-018-0406-3
W. Song, and Elbert E. M. Chia. Science Advances 9, eadd7856 (2023).