Electronic Transport and Terahertz Magnetospectroscopy Studies of BCS Superconductors in Cavities

There is currently a worldwide effort to uncover new states, phenomena, and phases in materials in optical cavities in the complete absence of any external fields other than the quantum vacuum, or zero-point, electromagnetic fields. Here, we present the results of our studies on thin films of superconductors inside terahertz cavities in search of some of the recently predicted phenomena of cavity-enhanced, cavity-mediated, and cavity-induced superconductivity. We measured the transition temperature of several niobium nitride thin films inside a Tamm cavity using electrical resistivity measurements. We also performed terahertz time-domain spectroscopy measurements to study the influence of one-dimensional photonic crystal cavity fields on the optical conductivity spectra of the films at various temperatures and magnetic fields. We analyzed the obtained results using BCS theory combined with recently proposed theoretical models. We will also discuss preliminary results obtained for other superconductors, including magnesium diboride, in cavities probed through similar transport and optical conductivity measurements.