M. V. Feigel’man, NANOCENTER, Ljubljana, Slovenia Floralis & LPMMC, University Grenoble-Alpes, France and L.D.Landau Institute for Theoretical Physics, Chernogolovka, Russia

Wednesday, January 31 at 2:00 pm (Paris time)

Room Charpak, entrance building, ground floor

Mean-field theory of first-order quantum superconductor-insulator transition

Recent experimental studies of strongly disordered Indium Oxide films revealed an unusual first-order quantum phase transition between superconducting and insulating state (SIT), with the jump between nonzero and zero values of superfluid stiffness at the transition. This finding is in sharp contradiction with a "scaling scenario" discussed usually in relation to SIT. In the present paper we propose a simple theory of this first-order transition. It is based upon the idea of competition between two intrinsically different ground states that can be formed by initially localized (due to strong disorder) electron pairs : superconducting state and Coulomb glass insulator. These two ground states are characterized by two crucially different order parameters, in the latter), thus it is natural to expect a discontinuous transition between them at T=0. The transition happens when magnitudes of superconducting gap Delta and Coulomb gap E_C are comparable.

We also extend our analysis to low nonzero temperatures and provide a mean-field "phase diagram" in the plane of (T/Delta, E_C/Delta)

* I. V. Poboiko is also associated to this work

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