Assembling dipolar quantum solids with semiconductor excitons

Condensed-mater systems offer a fascinating realm when spatially extendedinteractions have strengths exceeding thermal and kinetic energies. Many-bodyground-states are then governed by spatial order so that quantum crystalsemerge spontaneously. Here we report such quantum crystal for bosons, byassembling dipolar quantum solids made by two-dimensional excitons of GaAsbilayers. We trigger quantum crystallisation by preparing a Mott insulator withone exciton in every site of a shallow artificial lattice. In turn, the Mottphase self-defines a dipolar anti-lattice where additional excitons areconfined and spontaneously realise a checkerboard solid at half-filling. Weevidence that strong dipolar correlations effectively bound excitonic Mott andcheckerboard phases, while screening the artificial lattice confinement. Ourobservations thus show that lattice models with extended interactions provide afertile ground to emulate Wigner crystallisation.