Local imaging of the superfluid density at the LAO/STO interface as a function of gate voltage

ORAL

Abstract

The interface between two insulating oxides, LaAlO$_{3}$ and SrTiO$_{3}$, exhibits a two-dimensional electron system with high mobility, magnetism, superconductivity at low temperatures, and an electric-field-tuned superconductor-insulator transition. This interface has been studied extensively using transport and magnetization, which do not directly probe potential variation on a local length scale. We use a scanning SQUID microscope to locally probe superconductivity and magnetism in LAO/STO heterostructures. We measure the local diamagnetic susceptibility and critical temperature of as a function of position and gate voltage. Our local susceptibility measurement is related to the density of superconducting carriers which gives us a map of superfluid density. We find that the superfluid density is inhomogeneous, showing regions of susceptibility that varies over a large fraction of the total response while the critical temperature remains relatively uniform across the sample. Tracking the evolution of both of these parameters as a function of gate voltage and position enables investigation of the local onset of the superconductor-insulator transitions on both sides of the dome.

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Authors

  • Julie A. Bert

    • Stanford University, USA
    • Stanford Institute for Materials and Energy Sciences, Stanford University
    • Stanford Institute for Materials and Energy Science, Stanford University

  • Beena Kalisky

    • Stanford University, USA; Bar-Ilan University, Israel
    • Stanford Institute for Materials and Energy Sciences, Stanford University
    • Stanford University

  • Chris Bell

    • Department of Applied Physics and Stanford Institute for Materials and Energy Science, Stanford University,Stanford, California 94305, USA
    • Stanford University, USA
    • Stanford Institute for Materials and Energy Sciences, Stanford University
    • Stanford Univeristy

  • Yasuyuki Hikita

    • Department of Applied Physics and Stanford Institute for Materials and Energy Science, Stanford University,Stanford, California 94305, USA
    • Stanford Institute for Materials and Energy Sciences, Stanford University

  • Harold Hwang

    • Department of Applied Physics and Stanford Institute for Materials and Energy Science, Stanford University,Stanford, California 94305, USA
    • Stanford University, USA
    • Stanford Institute for Materials and Energy Sciences, Stanford University
    • Stanford University
    • Stanford University and SLAC National Accelerator Laboratory

  • Kathryn Moler

    • Stanford University, USA
    • Stanford Institute for Materials and Energy Sciences, Stanford University
    • Stanford University