From Atomic Layers to Moire Superlattices: Engineering Quantum Interfaces in 2D Heterostructures for Next Generation Terahertz Optoelectronics

The terahertz spectral domain embodies the fundamental energy scales of charge transport, collective excitations, and many-body quantum interactions, yet has historically conventional platforms (GaAs, ZnTe) that reach this domain but lack the tunability and confinement of 2D materials. The emergence of 2D quantum materials has initiated a profound shift in this landscape, enabling THz light-matter interaction to be engineered at the level of atomic layers and interfaces rather than dictated by bulk electronic structure. This review articulates a materials-by-design framework for next-generation THz optoelectronics, progressing from isolated 2D crystals to van der Waals heterostructures and moiré superlattices. We highlight how reduced dimensionality and enhanced Coulomb interactions give rise to unconventional THz electrodynamics in graphene and transition metal dichalcogenides, while magnetic 2D materials and MXenes introduce low-energy spin, charge, and lattice excitations that expand THz functionality beyond purely electronic transport. Interfacial assembly without lattice constraints enables programmable band alignment, charge redistribution, and coherent hybridization across the materials. Beyond static heterostructures, twist-angle-based moiré superlattices introduce reconfigurable quantum energy landscapes, flat electronic bands, and correlated quasiparticles whose intrinsic energy scales align naturally with the THz regime. These developments elevate interfaces and moiré potentials to active design parameters for controlling low-energy optical and electronic response. Ultrafast terahertz spectroscopy emerges as a unifying tool that directly links quantum materials physics to device functionality by resolving transient conductivity, interfacial charge transfer, and collective dynamics on ultrafast timescales. By integrating spectroscopic insight with scalable synthesis and device architectures, this review outlines a forward-looking vision in which quantum interface engineering establishes a new paradigm for THz photonics, positioning 2D heterostructures as foundational materials for future information, sensing, and quantum technologies.