Mapping topological and magnetic transitions in semiconductor moiré materials

Semiconductor moiré lattices provide a flexible platform to study flat, topological bands which host a variety of closely competing correlated states. In this talk, I will present single-electron transistor microscopy of WSe₂ bilayers at low twist angles, where interaction effects are most prominent. At zero magnetic field, we observe a series of quantum anomalous Hall states and demonstrate topological phase transitions as a function of twist angle and electric field. We also investigate the Hofstadter regime at high magnetic field, where we resolve a cascade of magnetic phase transitions due to crossing Hofstadter and moiré bands of differing spin. I will discuss which experimental tuning knobs are most influential in determining the preferred ground states and symmetry breaking within different physical regimes.