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

TL;DR

This paper demonstrates the realization of dual Bose-Fermi density waves in a GaAs bilayer system by confining neutral and charged dipolar excitons in a lattice, revealing new quantum phases with controlled interactions.

Contribution

It introduces a method to manipulate Bose-Fermi mixtures of dipolar excitons in a lattice, showing the formation of dual density waves with species ordered in stripes.

Findings

Stable insulating phases at specific charged exciton fractions.

Observation of alternating stripe density waves of neutral and charged excitons.

Dipolar excitons enable controlled simulation of extended Bose-Fermi Hubbard models.

Abstract

Strongly correlated quantum particles in lattice potentials are the building blocks for a large variety of quantum insulators, for instance Mott phases and density waves breaking the lattice symmetry. Such collective states are accessible to bosonic and fermionic systems. To expand further the spectrum of accessible quantum matter phases, mixing both species is theoretically appealing, since density order then competes with phase separation. Here we manipulate such 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 intra-species interactions stabilise 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 realised, 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.