This open access book represents an outstanding contribution to the study of light matter interaction in quantum materials. It establishes that van der Waals heterostructures naturally act as terahertz plasmonic cavities, in which confined electromagnetic modes strongly couple to electronic excitations. This discovery reframes the low-energy electrodynamics of two-dimensional materials and provides a foundation for exploring cavity-mediated quantum phenomena in the solid state. Equally significant is the development of an on-chip terahertz spectroscopy platform capable of measuring the optical conductivity of gate-tunable two-dimensional materials in the near field. This experimental advance overcomes longstanding diffraction and sensitivity limits, opening new routes to probe collective excitations in micro-structured quantum material devices. This book is exemplary in its combination of conceptual depth, technical precision, and clarity of presentation. It is likely to serve as a reference for future studies of cavity-coupled and non-equilibrium phenomena in low-dimensional systems.
