Symmetry-Breaking-Driven Terahertz Nonlinearity in Topological van der Waals Heterostructures for Broadband Wireless Communication

The development of high-performance nonlinear mixers is a prerequisite for frequency down-conversion and signal processing in the burgeoning era of 6G terahertz (THz) technology. However, conventional terahertz mixers often suffer from the impossible trinity of high local oscillator power, cryogenic cooling requirement, and limited intermediate frequency bandwidths. Here, we demonstrate that vertical van der Waals heterostructures integrating topological Dirac semimetal NiTe2 and graphene exhibit giant room-temperature terahertz nonlinear response driven by symmetry-breaking-induced skew scattering at topological surface states. This intrinsic nonlinear mechanism enables efficient heterodyne frequency conversion without external bias or sophisticated circuitry. The fabricated devices achieve an unprecedented intermediate frequency bandwidth exceeding 108 GHz and a minimum detectable power below − 25 dBm at room temperature. Leveraging the broadband response, we demonstrate stable frequency down-conversion and coherent signal transmission over 800-meter free-space links and wireless image transfer with high fidelity, confirming the capability for real-world digital communication. The passive, scalable architecture of topological heterostructure mixers offers a materials-driven pathway toward low-power, chip-integrated terahertz transceivers for 6G networks and airborne communication platforms.