Superconducting fluctuations and giant negative magnetoresistance in a gate-voltage tuned two-dimensional electron system with strong spin-orbit impurity scattering

Field-induced boson insulating states in a 2D superconducting electron gas with strong spin–orbit scatterings

“…For answering this intriguing question we note our use of the time-dependent Ginzburg-Landau (TDGL) functional approach in consistently evaluating the AL and the DOS conductivities. Within this exclusive boson approach we have found in [1] that at low temperatures the (negative) DOS conductivity prevails over the AL paraconductivity at fields that roughly indicate the presence of the observed enhanced MR. Dynamical quantum tunneling of Cooper-pair fluctuations out of mesoscopic puddles has been introduced into the theory within a complementary phenomenological approach, including the contribution of unpaired normal electron states, to account for the observed experimental data.…”

“…responsible for the AL paraconductivity. In this approach the entire underlying information about the thin film of pairing electrons system (which includes in-plane spin-orbit scatterings, Zeeman spin splitting as well as out-of-plane diamagnetic energy [1]) is incorporated in the inverse fluctuation propagator (in wavevector-frequency representation) D −1 (q+2eA/ℏ, ω), mediating between the order parameter and the GL functional. In the Gaussian approximation the relation is quadratic, i.e.…”

“…so that the coupling to the external electromagnetic field takes place directly through the vertex of the Cooper-pair current, defined in equation (1).…”

“…In a recent paper [1] we have shown that Cooper-pair fluctuations in a 2D electron gas with strong spin-orbit scatterings can lead at low temperatures to pronounced magnetoresistance (MR) peaks above a crossover field to superconductivity. The model was applied to the high mobility electron systems formed in the electron-doped interfaces between two insulating perovskite oxides-SrTiO 3 and LaAlO 3 [2,3], showing good quantitative agreement with a large body of experimental sheet-resistance data obtained under varying gate voltage [4].…”

“…The most intriguing question arising from the Cooper-pair fluctuations scenario of the superconductor-insulator transition (SIT) presented in [1] is how Cooper-pairs liquid, whose condensation (in momentum space) is customarily associated with superconductivity, could metamorphose into an insulator just by lowering its temperature under sufficiently high magnetic field? For answering this intriguing question we note our use of the time-dependent Ginzburg-Landau (TDGL) functional approach in consistently evaluating the AL and the DOS conductivities.…”