Dipolar Excitonic Quantum Wires at Atomically Sharp Lateral Interfaces

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.