Origin of nonlinear photocurrents in chiral multifold semimetals
Nonlinear photocurrents in topological semimetals encode quantum geometric characters of Bloch wavefunctions and band topology, and offer new opportunities for advanced photovoltaics. Dr. Yao-Jui Chan and Yu-Chieh Wen from the Institute of Physics have characterized the nonlinear photoconductivities of chiral multifold semimetal CoSi through a refined THz emission spectroscopy. The results reveal a large linear shift conductivity (17 μA/V2), and confirm a giant injection conductivity (167 μA/V2) as a consequence of strongly interfered non-quantized contributions from the vicinity of multifold nodes with opposite chiralities. Bulk transverse injection currents and weak nonlocal photon drag effect are also identified. This work not only addresses the nonlinear optical origin of photocurrents in chiral transition metal monosilicides, but also highlights their potential for mid-infrared photovoltaics via various nonlinear optical channels. This work was conducted in collaboration with Sankar Raman, Hsin Lin, Wei-Li Lee, Min-Nan Ou groups in IoP, and selected as Editor’s Suggestion in Physical Review B.
Journal Links: https://journals.aps.org/prb/abstract/10.1103/PhysRevB.110.L201118