Twisted Layers and Trapped Light: The Rise of Moiré Excitons

Physicists are uncovering a fertile territory for new physics by manipulating the geometry of two-dimensional semiconductors. When these atomic sheets are stacked in twisted or lattice-mismatched layers, they create moiré patterns—a periodic potential landscape that dramatically alters electronic behaviour. This landscape confines excitons (pairs of electrons and holes), granting them long lifetimes and fostering strong dipolar interactions.

According to a recent review, this confinement allows researchers to engineer 'flat bands' and localised states, opening pathways to realise strongly correlated phases like excitonic insulators, superfluids, and supersolids. Significantly, the text suggests these phases could potentially be stable at room temperature, moving beyond the cryogenic requirements of conventional systems. Furthermore, when these materials are embedded in optical cavities, moiré excitons hybridise with photons to form 'moiré exciton-polaritons'. These new quasiparticles bridge nanophotonics and correlated electron systems, exhibiting enhanced optical nonlinearities and novel topological features ideal for quantum simulation and optoelectronics.