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Jauary 29 at 4:30 pm (Paris time) !Unusual time !
Room Holweck, building C, 1st floor, 10 rue Vauquelin, ESPCI
Quantum breakdown of a pinned vortex glass near the superconductor-insulator transition
The interplay between disorder and vortex-vortex interactions in strongly disordered superconductors under magnetic fields produces a glassy superfluid state, characterized by strong vortex pinning without local positional order. Understanding this state is crucial, as it precedes the quantum breakdown of superconductivity at the critical magnetic field, Bc . Here, using plasmonic microwave spectroscopy in superconducting resonators patterned on amorphous indium oxide thin films, we directly track the evolution of superfluid density as a function of the perpendicular magnetic field up to Bc. Remarkably, we observe an unusual logarithmic suppression of superfluid density arising from a novel form of collective vortex pinning mediated by vortex-vortex interactions. This suppression occurring over three orders of magnitudes in the magnetic field terminates linearly at a quantum critical point independently confirmed through magnetoresistance measurements, revealing a continuous quantum phase transition, in contrast to the abrupt transition observed at zero field. We further uncover strong nonlinear electromagnetic response of the vortex glass pinning, which emerges as a substantial anti-Kerr effect of potential relevance for quantum sensing under magnetic field. Our findings elucidate how disorder determines the critical magnetic field and clarify the nature of the magnetic-field-induced superconductor-insulator transition. Importantly, very similar dependencies on magnetic field are found for indium oxide films with quite different disorder, both in the semiclassical limit far from disorder-induced SIT, and in the pseudo-gap region close to SIT.
* coauthors : David Perconte, Thibault Charpentier, Florent Blondelle, Frédéric Gay, Viktor Kabanov, Nicolas Roch, and Benjamin Sacépé
