Near power-law temperature dependence of the superfluid stiffness in strongly disordered superconductors
In BCS superconductors, the superfluid stiffness is virtually constant at low temperature and only slightly affected by the exponentially low density of thermal quasiparticles. Here, we present an experimental and theoretical study on the temperature dependence of superfluid stiffness in a strongly disordered pseudogaped superconductor, amorphous InOx, which exhibits non-BCS behavior. We report an unusual power-law suppression of the superfluid stiffness measured via the frequency shift of microwave resonators. This power-law dependence at low temperature demonstrates the existence of low-energy collective excitations and the presence of a new channel of dissipation in inhomogeneous superconductors. Our findings have implications for the use of strongly disordered superconductors as superinductance in quantum circuits.
Anton V. Khvalyuk, Thibault Charpentier, Nicolas Roch, Benjamin Sacépé, and Mikhail V. Feigel’man
