title: Quantum interference in an interfacial superconductor.
abstract: The two-dimensional superconductor that forms at the interface between the complex oxides lanthanum aluminate (LAO) and strontium titanate (STO) has several intriguing properties that set it apart from conventional superconductors. Most notably, an electric field can be used to tune its critical temperature (Tc; ref. 7), revealing a dome-shaped phase diagram reminiscent of high-Tcsuperconductors. So far, experiments with oxide interfaces have measured quantities that probe only the magnitude of the superconducting order parameter and are not sensitive to its phase. Here, we perform phase-sensitive measurements by realizing the first superconducting quantum interference devices (SQUIDs) at the LAO/STO interface. Furthermore, we develop a new paradigm for the creation of superconducting circuit elements, where local gates enable the in situ creation and control of Josephson junctions. These gate-defined SQUIDs are unique in that the entire device is made from a single superconductor with purely electrostatic interfaces between the superconducting reservoir and the weak link. We complement our experiments with numerical simulations and show that the low superfluid density of this interfacial superconductor results in a large, gate-controllable kinetic inductance of the SQUID. Our observation of robust quantum interference opens up a new pathway to understanding the nature of superconductivity at oxide interfaces.
authors.affiliation: Kavli Institute of Nanoscience, Delft University of Technology, PO Box 5046, 2600 GA Delft, The Netherlands.
authors.forename: Srijit
authors.initials: S
authors.lastname: Goswami
authors.affiliation: Kavli Institute of Nanoscience, Delft University of Technology, PO Box 5046, 2600 GA Delft, The Netherlands.
authors.forename: Emre
authors.initials: E
authors.lastname: Mulazimoglu
authors.affiliation: Kavli Institute of Nanoscience, Delft University of Technology, PO Box 5046, 2600 GA Delft, The Netherlands.
authors.forename: Ana M R V L
authors.initials: AM
authors.lastname: Monteiro
authors.affiliation: Physikalisches Institut and CQ Center for Quantum Science in LISA+, Eberhard Karls Universität Tübingen, Auf der Morgenstelle 14, D-72076 Tübingen, Germany.
authors.forename: Roman
authors.initials: R
authors.lastname: Wölbing
authors.affiliation: Physikalisches Institut and CQ Center for Quantum Science in LISA+, Eberhard Karls Universität Tübingen, Auf der Morgenstelle 14, D-72076 Tübingen, Germany.
authors.forename: Dieter
authors.initials: D
authors.lastname: Koelle
authors.affiliation: Physikalisches Institut and CQ Center for Quantum Science in LISA+, Eberhard Karls Universität Tübingen, Auf der Morgenstelle 14, D-72076 Tübingen, Germany.
authors.forename: Reinhold
authors.initials: R
authors.lastname: Kleiner
authors.affiliation: Kavli Institute of Nanoscience, Delft University of Technology, PO Box 5046, 2600 GA Delft, The Netherlands.
authors.forename: Ya M
authors.initials: YM
authors.lastname: Blanter
authors.affiliation: Kavli Institute of Nanoscience, Delft University of Technology, PO Box 5046, 2600 GA Delft, The Netherlands.
authors.forename: Lieven M K
authors.initials: LM
authors.lastname: Vandersypen
authors.affiliation: Kavli Institute of Nanoscience, Delft University of Technology, PO Box 5046, 2600 GA Delft, The Netherlands.
authors.forename: Andrea D
authors.initials: AD
authors.lastname: Caviglia