Terahertz Nanoscopy on Low-Dimensional Materials: Toward Ultrafast Physical Phenomena

Low-dimensional materials (LDMs) with unique electromagnetic properties and diverse local phenomena have garnered significant interest, particularly for their low-energy responses within the terahertz (THz) range. Achieving deep subwavelength resolution, THz nanoscopy offers a promising route to investigate LDMs at the nanoscale. Steady-state THz nanoscopy has been demonstrated as a powerful tool for investigating light-matter interactions across boundaries and interfaces, enabling insights into physical phenomena such as localized collective oscillations, quantum confinement of quasiparticles, and metal-to-insulator phase transitions (MITs). However, tracking the ultrafast nonequilibrium dynamics of LDMs remains challenging. Ultrafast THz nanoscopy, with femtosecond temporal resolution, provides a direct pathway to investigate and manipulate the motion of, for example, charges, currents, and carriers at ultrashort time scales. In this review, we focus on recent advances in THz nanoscopy of LDMs, with particular emphasis on the ultrafast dynamics of light-matter interaction. We provide a concise overview of recent advances and suggest future research directions in this impactful field of interdisciplinary science.