Abstract
In LaAlO3/SrTiO3 heterostructures, a gate tunable superconducting electron gas is confined in a quantum well at the interface between two insulating oxides. Remarkably, the gas coexists with both magnetism and strong Rashba spin–orbit coupling. However, both the origin of superconductivity and the nature of the transition to the normal state over the whole doping range remain elusive. Here we use resonant microwave transport to extract the superfluid stiffness and the superconducting gap energy of the LaAlO3/SrTiO3 interface as a function of carrier density. We show that the superconducting phase diagram of this system is controlled by the competition between electron pairing and phase coherence. The analysis of the superfluid density reveals that only a very small fraction of the electrons condenses into the superconducting state. We propose that this corresponds to the weak filling of high-energy dxz/dyz bands in the quantum well, more apt to host superconductivity.
Highlights
In LaAlO3/SrTiO3 heterostructures, a gate tunable superconducting electron gas is confined in a quantum well at the interface between two insulating oxides
The superconducting phase diagram of LaAlO3/SrTiO3 interfaces defined by plotting the critical temperature Tc as a function of electrostatic doping has the shape of a dome
It is embedded into an RLC resonant circuit whose inductor L1 and resistor R1 are surface mounted microwave devices (SMDs), and whose capacitor CSTO is due to the substrate in parallel with the 2D electron gas (2-DEG) (Fig. 1a, c)
Summary
The. LaAlO3/SrTiO3 heterostructure is inserted in a microwave circuit board, between the central strip of a coplanar waveguide guide (CPW) transmission line and its ground. LaAlO3/SrTiO3 heterostructure is inserted in a microwave circuit board, between the central strip of a coplanar waveguide guide (CPW) transmission line and its ground It is embedded into an RLC resonant circuit whose inductor L1 and resistor R1 are surface mounted microwave devices (SMDs), and whose capacitor CSTO is due to the substrate in parallel with the 2D electron gas (2-DEG) (Fig. 1a, c). ZL(ω) is the impedance of the RLC circuit represented, whose resonance frequency ω0 in the superconducting state is directly related to the kinetic inductance of the 2-DEG. In the limit ω ( τÀ1 (τ is the elastic scattering time) and for temperatures higher than Tc, the 2-DEG behaves as
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