Superconducting Cavity Probes Sliding Ferroelectricity in Small-Angle Twisted WSe₂

Ferroelectricity is a property of materials that exhibits spontaneous charge polarization. Ferroelectricity in 2D materials is interesting because of its applications in memory devices and field-effect transistors. Recently, a new type of ferroelectricity, known as sliding ferroelectricity, has been discovered, in which parallel-stacked bilayers of hexagonal boron nitride (hBN) or transition metal dichalcogenides (TMDCs) develop an out-of-plane electric polarization. In this work, we probe the polarization of small-angle parallel-stacked WSe₂ by measuring its high-frequency AC response, achieved by embedding it into a half-wave superconducting coplanar waveguide cavity. We observe a hysteretic response in the capacitance of the stack and the quality factor of the cavity, confirming ferroelectric switching in the system. Our results further reveal relaxation effects associated with the ferroelectric domain wall motion. This cavity-based technique has potential applications in probing domain wall dynamics in a ferroelectric system at high frequencies.