Bimodal Phase Diagram of the Superfluid Density in LaAlO3/SrTiO3 Revealed by an Interfacial Waveguide Resonator

TL;DR

This study maps the superconducting phase diagram of LaAlO3/SrTiO3 interfaces using a waveguide resonator, revealing a dome-shaped dependence of superfluid density and transition temperature, and interpreting the ground state as a Josephson junction array.

Contribution

It introduces a novel interfacial waveguide resonator technique to probe the superfluid density and phase diagram of LaAlO3/SrTiO3, providing new insights into its superconducting properties.

Findings

Superfluid density and transition temperature follow a dome shape.

Superconducting ground state resembles a Josephson junction array.

Transition from long- to short-range order with doping.

Abstract

We explore the superconducting phase diagram of the two-dimensional electron system at the LaAlO3/SrTiO3 interface by monitoring the frequencies of the cavity modes of a coplanar waveguide resonator fabricated in the interface itself. We determine the phase diagram of the superconducting transition as a function of temperature and electrostatic gating, finding that both the superfluid density and the transition temperature follow a dome shape, but that the two are not monotonically related. The ground state of this 2DES is interpreted as a Josephson junction array, where a transition from long- to short-range order occurs as a function of the electronic doping. The synergy between correlated oxides and superconducting circuits is revealed to be a promising route to investigate these exotic compounds, complementary to standard magneto-transport measurements.