Electrically controlled interlayer trion fluid in electron-hole bilayers

The combination of repulsive and attractive Coulomb interactions in a quantum electron(e)-hole(h) fluid can produce correlated phases of multiparticle charge complexes such as excitons, trions, and biexcitons. We report an experimental realization of an electrically controlled interlayer trion fluid in van der Waals heterostructures. In strongly coupled electron-hole bilayers, electrons and holes spontaneously form three-particle trion bound states. The interlayer trions can assume 1e-2h and 2e-1h configurations. We show that the two holes in 1e-2h trions form a spin-singlet with a ~1meV spin gap. By electrostatic gating, the equilibrium state can be continuously tuned into an exciton fluid, a trion fluid, an exciton-trion mixture, or a trion-charge mixture. Our work demonstrates a unique platform to study correlated phases of tunable Bose-Fermi mixtures.