Terahertz interface physics: from terahertz wave propagation to terahertz wave generation

Abstract Terahertz (THz) interface physics as a new interdiscipline between the THz technique and condensed matter physics has undergone rapid development in recent years. In particular, the development of advanced materials, such as graphene, transitional metal dichalcogenides, topological insulators, ferromagnetic metals, and metamaterials, has revolutionized the interface field and further promoted the development of THz functional devices based on interface physics. Moreover, playing at the interface of these advanced materials could unveil a wealth of fascinating physical effects such as charge transfer, proximity effect, inverse spin-Hall effect, and Rashba effect with THz technology by engineering the charge, spin, orbit, valley, and lattice degrees of freedom. In this review, we start with a discussion of the basic theory of THz interface physics, including interface formation with advanced materials, THz wave reflection and transmission at the interface, and band alignment and charge dynamics at the interface. Then we move to recent progress in advanced materials from THz wave propagation to THz wave generation at the interface. In THz wave propagation, we focus on THz wave impedance-matching, Goos–Hänchen and Imbert–Fedorov shifts in THz region, interfacial modulation and interfacial sensing based on THz waves. In THz wave generation, we summarize ongoing coherent THz wave generation from van der Waals interfaces, multiferroic interfaces, and magnetic interfaces. The fascinating THz interface physics of advanced materials is promising and promotes novel THz functional devices for manipulating propagation and generation of THz waves at interfaces.