Kadow, Wilhelm - Technical University of Munich

From Bose-Fermi Mixtures to Kinetic Magnetism in Moiré Heterostructures

Moiré heterostructures are fascinating experimental platforms for studying emergent quantum many-body phenomena. Here, we realize an equilibrium Bose-Fermi mixture in a bilayer electron system implemented in a WS2/WSe2 moiré heterobilayer with strong Coulomb coupling to a nearby moiré-free WSe2 monolayer. Absent the fermionic component, the underlying bosonic phase manifests as a dipolar excitonic insulator. By injecting excess charges into it, we show that the bosonic phase forms a stable mixture with added electrons but abruptly collapses upon hole doping. We develop a microscopic model to explain the unusual asymmetric stability.

Moreover, a similar setup can realize an approximate SU(4)-symmetric Hubbard model. Using matrix product states, we theoretically investigate the magnetic order upon hole doping, where several competing states emerge due to kinetic magnetism.