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TT: Fachverband Tiefe Temperaturen

TT 21: Focus Session: Strongly Disordered Superconductors

TT 21.1: Invited Talk

Tuesday, March 19, 2024, 09:30–10:00, H 0104

The fate of the superfluid density near the superconductor-insulator transition — •Benjamin Sacepe — Neel Institute, CNRS Grenoble, France

Superconducting films of amorphous Indium Oxide (a:InO) undergo a transition to insulation with increasing disorder, which is due to the localization of pre-formed Cooper pairs. The continuous decrease in critical temperature as critical disorder is approached suggests an equally continuous suppression of superfluid density. In this talk I will discuss a systematic study of the superfluid density measured via plasmon dispersion spectroscopy of microwave resonators made of a:InO, combined with DC resistivity measurements, as a function of disorder. We observed that the superfluid stiffness defines the superconducting critical temperature over a wide range of disorder, highlighting the dominant role of phase fluctuations. Furthermore, we found that the superfluid density remains surprisingly finite at the critical disorder, indicating an unexpected first-order nature of the disorder-driven quantum phase transition to insulator.

Keywords: Strongly disordered superconductors; Superconductor-insulator transition; Phase fluctuations; Superinductance