Contact-free RF detection of moiré phases via superconducting cavity coupling

Magic-angle twisted trilayer graphene (MATTG) has emerged as a platform for exploring correlated and superconducting phases arising from flat electronic bands. However, conventional transport measurements often obscure fragile states due to contact-induced perturbations. Here, we implement a non-invasive sensing technique based on cavity quantum electrodynamics to probe electronic phases in MATTG. In our setup, a superconducting microwave resonator is embedded in a transmission-line geometry, with the MATTG device acting as one of the coupling capacitors of the cavity. This arrangement allows the cavity's resonant frequency and transmission signals to respond sensitively to changes in the electronic properties of the moiré system. By monitoring these shifts, we can infer variations in quantum capacitance, correlated behavior, and also the superfluid density of the system without the need for direct current flow. Our results establish a general framework for interfacing moiré materials with superconducting circuits, enabling phase-sensitive, contact-free readout and providing a platform to study the real-time dynamics of correlated electronic phases.