Dual-density waves with neutral and charged dipolar excitons of GaAs bilayers

Strongly correlated quantum particles in lattice potentials are the building blocks for a wide variety of quantum insulators—for instance, Mott phases and density waves breaking lattice symmetry^1–3. Such collective states are accessible to bosonic and fermionic systems^{2,4–10,11,12}. To expand further the spectrum of accessible quantum matter phases, mixing both species is theoretically appealing because density order then competes with phase separation^13–16. Here we manipulate such a Bose–Fermi mixture by confining neutral (boson-like) and charged (fermion-like) dipolar excitons in an artificial square lattice of a GaAs bilayer. At unitary lattice filling, strong inter- and intraspecies interactions stabilize insulating phases when the fraction of charged excitons is around (1/3, 1/2, 2/3). We evidence that dual Bose–Fermi density waves are then realized, with species ordered in alternating stripes. Our observations highlight that dipolar excitons allow for controlled implementations of Bose–Fermi Hubbard models extended by off-site interactions.