Giant Photogalvanic Effect-Induced Terahertz Wave Emission in Wafer-Scale Type-II Dirac Semimetal PtTe₂

Terahertz (THz) emission arising from the second-order nonlinear photocurrent effects in two-dimensional quantum materials has attracted significant attention due to its high efficiency and ease of polarization manipulation. However, in centrosymmetric quantum materials, the terahertz emission is typically suppressed, caused by the directional symmetry of the photocurrent generated under femtosecond laser excitation. In this work, we report that wafer-scale type-II Dirac semimetal PtTe₂ with lattice centrosymmetry exhibits remarkably high THz emission efficiency (2 orders of magnitude greater than that of a ZnTe nonlinear crystal with equivalent thickness) and pronounced polarization sensitivity at room temperature. The THz emission of the PtTe₂ films grown on Al₂O₃ substrates by molecular beam epitaxy could be attributed to the photogalvanic effect (PGE) when the lattice centrosymmetry would be broken by strain from the substrates. Our finding indicates that wafer-scale PtTe₂ could be a promising candidate for efficient THz emission at room temperature under femtosecond laser excitation.