Abstract
Optical Materials Express 2025, 15, 1765-1776
On-chip terahertz emission from Floquet-Bloch states [Invited]
Li X, Hagelstein J, Sturm F, Kusyak K, Aranzadi JI, Kipp G, Huang Y, Schulte BF, Potts AM, Quirós-Cordero V, Trovatello C, Peng ZH, Hu C, DeStefano JM, Taniguchi T, Wantanabe K, Sentef MA, Shin D, Schuck PJ, Xu X, Chu JH, Bretscher HM, Day MW, McIver JW
Floquet engineering uses time-periodic electromagnetic fields to modify the electronic properties of quantum materials via the creation of Floquet-Bloch states. These photon-dressed states inherit features from both the material and the driving field, enabling the exploration and control of quantum phenomena in light-matter hybrid systems. In non-centrosymmetric materials, shift currents can arise from the quantum geometric properties of electronic wavefunctions. However, shift currents from Floquet-Bloch states remain experimentally unexplored. Here, we employ an on-chip optoelectronic circuit to detect intrinsic terahertz emission from Floquet-Bloch states in Td-WTe2 under intense optical driving. We observe strong edge-localized terahertz emission that scales linearly with the driving field, consistent with the theoretical prediction for shift currents generated by Floquet-Bloch states. The results advance our understanding of strongly driven quantum materials and provide insights for developing efficient, bias-free terahertz sources for future optoelectronic technologies.