Dipolar Excitonic Quantum Wires at Atomically Sharp Lateral Interfaces

Abstract One-dimensional (1D) quantum systems are a cornerstone of condensed matter physics. However, their realization in solids has traditionally relied on top-down methods, which are limited by structural disorder and coarse confinement. Here, we demonstrate a fundamentally new route to low-dimensional systems: the emergence of 1D quantum matter at the atomically sharp interface between monolayer semiconductors. Using lateral MoSe2–WSe2 heterostructures, we identify interfacial excitonic quasiparticles bound to the crystal junction. Photoluminescence spectroscopy resolves these excitons into a ladder of discrete states, establishing 1D confinement at length scales ≲3 nm. These excitons possess exceptionally large permanent in-plane electric dipole moments exceeding e × 2 nm, and exhibit micron-scale anisotropic diffusion confined to the interface. By introducing electrostatic doping, we demonstrate a collapse of the dipole moment and a 20-fold reduction in lifetime. By dynamically tuning wavefunctions within a single atomic monolayer, we open a scalable route toward engineering 1D quantum matter.