Interplay Between Cavity Quantum Electrodynamics and Superconductivity

Light–matter interaction is a promising route to alter and control the macroscopic properties of superconductors and provide new insights into microscopic mechanisms behind superconductivity. Observations of laser-induced superconducting-like states above the equilibrium critical temperature (T_c) have been reported, but these effects are transient, and their microscopic mechanisms remain enigmatic. To address these issues, an alternative, complementary approach is to couple a superconductor with the quantum vacuum fluctuation field inside a cavity, which lifts the necessity of external laser pumping. Such an approach is predicted to change T_c and may also lead to Cooper pair formation in a non-superconductor mediated by cavity photons. Here, we report on the design, fabrication, and characterization of terahertz cavities for both BCS and unconventional superconducting thin films to modify their superconducting properties. We performed initial studies on 12 nm and 25 nm thin films of YBCO using terahertz time-domain spectroscopy and temperature-dependent electrical transport measurements. The obtained results will be analyzed using existing theoretical models, and future steps for uncovering new phenomena in the superconductor cavity light–matter coupled system will be discussed.