Effect of disorder on superconductivity and Rashba spin-orbit coupling in LaAlO3 / SrTiO3 interfaces

Abstract

A rather unique feature of the two-dimensional electron gas (2-DEG) formed at the interface between the two insulators LaAlO3 and SrTiO3 is to host both gate-tunable superconductivity and strong spin-orbit coupling. In the present work, we use the disorder generated by Cr substitution of Al atoms in LaAlO3 as a tool to explore the nature of superconductivity and spin-orbit coupling in these interfaces. A reduction of the superconducting Tc is observed with Cr doping consistent with an increase of electron-electron interaction in presence of disorder. In addition, the evolution of spin-orbit coupling with gate voltage and Cr doping suggests a D'Yakonov-Perel mechanism of spin relaxation in the presence of a Rashba-type spin-orbit interaction.

Gap suppression at a Lifshitz transition in a multi-condensate superconductor

“…The (110)-oriented LaAlO 3 /SrTiO 3 interface displays a Hall effect linear with magnetic field for V G < V opt G =-10V as expected for single band transport. For V G > V opt G , a nonlinear Hall effect is observed due to the filling of a second band ( Supplementary Figure 1) [12,31]. The carrier density n Hall = B eR Hall , reported in Fig.1e of the main text, which is extracted from R Hall in the limit B→0, is only meaningful in the linear regime.…”

“…In SrTiO 3 -based interfaces, the gate dependence of the 2-DEG carrier density can be extracted by combining Hall effect and gate capacitance measurements [12,31]. The Hall resistance R H is linear with the magnetic field B in the UD regime as expected for one-band transport (labelled band 1).…”

“…The new band (band 2) filling threshold, i.e. the Lifshitz transition, corresponds to the gate value where n Hall deviates from n 2DEG [12,31]. Interestingly, this transition occurs at the optimal doping point (V opt G −10V ), which establishes a correlation between the OD superconducting regime and the two-band transport regime observed in the normal state.…”

A possible superconductor-like state at elevated temperatures near metal electrodes in an LaAlO3/SrTiO3 interface

“…Insertion of external dopants into the interface changes the electric population of these orbitals. A variety of studies have been performed on doping: superconductivity is weakened by Cr doping 25 , electronic transport is not significantly affected by Tm and Lu doping 26,27 , electron density and mobility are quenched by Mn doping 28 , and the magnetic order is not affected by Ru doping 29 . However, it is difficult to find evidence for the enhancement of carrier mobility due to doping in these reports.…”

Manifold field effects at a complex oxide interface

“…The shape of this deviation is strongly reminiscent of weak antilocalization, a quantum interference phenomenon indicative of strong spin relaxation. In previous reports on LaAlO 3 -SrTiO 3 interfaces, the timescales involved with this relaxation were estimated by fitting this low-field magnetotransport to known WAL theories, enabling calculation of the spin-orbit coupling strength (25,54,55,124,126,185,(276)(277)(278) and even of the Landé gfactor (25).…”