Our latest manuscript on the electrodynamics of ultra-thin NbN superconducting films is now available on arXiv! You can read the preprint here.
Led by Meenakshi Sharma and Hrishikesh Borah from our group, this work is part of our long-term collaboration with S.P. Singh’s group at CSIR in New Delhi and with collaborators at IFW Dresden.
In this work, we investigate superconductivity in the strongly disordered regime. Ultra-thin NbN films exhibit exceptionally high kinetic inductance, reaching over 300 pH per square, while maintaining relatively high critical temperatures. This makes them attractive for a wide range of superconducting quantum devices. However, the large kinetic inductance reflects reduced superfluid stiffness, which strongly influences the microwave electrodynamic response, yet remains hidden in conventional transport measurements. By measuring the temperature-dependent response of microwave resonators fabricated from NbN films of different thicknesses, we observed a clear crossover from conventional, gap-dominated superconductivity in thicker films to a regime in which phase fluctuations play an increasingly important role in thinner films.
These results provide new insight into the nature of superconductivity in disordered thin films and are relevant for the optimization of NbN-based quantum devices, where this material is widely used for superconducting qubits, parametric amplifiers, and single-photon detectors.
Congratulations and many thanks to everyone who contributed!
