Local microwave probes of excitons and fractional Chern insulators

A longstanding challenge in quantum materials is to experimentally access the emergent excitations that define interacting and topological phases. This challenge becomes particularly sharp when those excitations are intrinsically local, whether through spatially varying excitonic structure or through boundary modes tied to bulk topology. In this talk, I will show how local microwave electrodynamics provides a new route to this problem in transition metal dichalcogenide systems. I will first discuss recent advances in optically coupled microwave impedance microscopy, which enable spatially resolved spectroscopic measurements of excitonic excitations. I will then present local probe studies of twisted MoTe2​ bilayers in the fractional Chern insulator regime, where we resolve the evolution from metallic behavior to a state with insulating bulk and conductive edges. The observed edge response is consistent with bulk-boundary correspondence and further suggests the composite nature of the low-energy excitations. Taken together, these results demonstrate that local microwave probes can uncover collective quantum electrodynamics that is hidden to conventional bulk techniques.