Quantum-Geometry-Enabled Terahertz Rectification in the Weyl Semimetal TaP.

Abstract

Noncentrosymmetric crystals can rectify light into a direct current (DC) through the second-order nonlinear response governed by the Berry-curvature dipole (BCD), an effect that becomes particularly efficient for low-energy terahertz (THz) photons. Topological Weyl semimetals (WSMs), with their large Berry curvature near the Weyl points and intrinsically broken inversion symmetry, represent an ideal platform to realize this effect. However, directly experimentally demonstrating a BCD-driven photoresponse in the THz regime remains a significant challenge. Here, we demonstrate room-temperature, junction-free terahertz current rectification in type-I Weyl semimetal tantalum phosphide (TaP) explicitly driven by its intrinsic Berry curvature dipole. We observe that transverse THz polarization generates longitudinal photocurrents with a fast response time (0.96 μs) across a broad bandwidth (0.04-0.53 THz), directly confirming BCD-imposed momentum-space asymmetry and its topological origin. Operating as a room-temperature heterodyne mixer, the TaP device achieves a remarkable 25 dB conversion gain over a 20 GHz instantaneous intermediate-frequency (IF) bandwidth. These results establish Weyl semimetals as a paradigm for topological optoelectronics, where a deeper understanding of quantum geometric effects directly enables the development of high-performance terahertz devices for applications such as 6G wireless communication.