Field-Induced SIT in Disordered 2D Electron systems: The case of amorphous Indium-Oxide thin films

Abstract

The phenomenon of field-induced superconductor to insulator transition (SIT) in disordered 2D electron systems has been a subject of controversy since its discovery in the early 1990s. Here we present a phenomenological quantitative theory of this phenomenon which is not based exclusively on the boson-vortex duality used commonly in the field. Within a new low-temperature framework of the time-dependent Ginzburg-Landau (TDGL) functional approach to superconducting fluctuations we propose and develop a scenario in which bosons of Cooper-pair fluctuations (CPFs) condense and localize in real-space mesoscopic puddles under increasing magnetic field due to diminishing stiffness of the fluctuation modes at low temperatures in a broad range of momentum space. Quantum tunneled CPFs relieving the condensed mesoscopic puddles, which consequently pair break into fermionic quasi-particle excitations, dominate the thermally activated inter-puddles transport. The spatially shrinking puddles of CPFs, embedded in expanding normal-state regions, upon further increasing field, suppress the quasi-particle excitation gap and so lead to high-field negative magneto-resistance (MR). Application to amorphous Indium-Oxide thin films shows good quantitative agreement with experimental sheet resistance data. In particular, in agreement with the experiment at low temperatures (i.e. well below the quantum tunneling pair breaking "temperature"), the sheet resistance isotherms are predicted to show a single crossing point at a quantum critical field not far below the MR peak.