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