Disordered Superconductors

Understanding the role of interaction and disorder is at the heart of understanding of collective behavior of many-body quantum systems, such as High temperature superconductors, quantum Hall effect and superfluid He. In superconductors, where the order parameter is described by a complex order parameter with an amplitude and phase (Y=Deiq ), the presence of strong disorder poses an intriguing question: Is the destruction of the superconducting state always associated with the vanishing or the amplitude or could strong phase fluctuations destroy the superconducting state even when the amplitude of the superconducting pairing remains finite? The latter, if true, would give rise to novel electronic states with finite superconducting pairing amplitude but no global superconductivity. Over the past two years we have been addressing this question, by extracting all the key parameters in the superconducting state, on a set of NbN thin films with controlled amount of disorder. We use a number of experimental tools, such the low-temperature scanning tunneling microscope, a two coil mutual inductance technique for the measurement of penetration depth and conventional transport and magnetotransport at high fields and very low temperatures.

(To see our publications in this area go to the publications page)

Some more details can be found here:

Quaternary Borocarbides

Nanostructured Superconductors

Spin Polarization Measurements using PCAR