Abstract
One of the hallmark experiments of quantum transport is the observation of the quantized resistance in a point contact in GaAs/AlGaAs heterostructures. Being formed with split gate technology, these structures represent in an ideal manner equilibrium reservoirs which are connected only through a few electron mode channel. It has been a long standing goal to achieve similar experimental conditions also in superconductors. Here we demonstrate the formation of a superconducting quantum point contact (SQPC) with split gate technology in a two-dimensional superconductor, utilizing the unique gate tunability of the superfluid at the LaAlO3/SrTiO3 interface. When the constriction is tuned through the action of metallic split gates we identify three regimes of transport: First, SQPC for which the supercurrent is carried only by a few quantum transport channels. Second, superconducting island strongly coupled to the equilibrium reservoirs. Third, charge island with a discrete spectrum weakly coupled to the reservoirs.
Highlights
One of the hallmark experiments of quantum transport is the observation of the quantized resistance in a point contact in GaAs/AlGaAs heterostructures
Ever since the seminal experiments by van Wees et al.[1,2] on a quantum point contact formed with split gates in a semiconductor heterostructure, it has been a great experimental challenge to achieve similar experimental conditions in superconductors[3]
The creation of a superconducting quantum point contact (SQPC) with split gates in LAO/STO should be within reach [cf
Summary
Split gate control of a quantum constriction. Our samples are fabricated following the procedure described by Goswami et al.[7]. (see Methods section and Supplementary Table 1). The measurements discussed in the main text were obtained from a single device, further measurements from a second sample are provided in the Supplementary Note 7. The metallic split gates (yellow) L and R cover the full width of the 5 μm wide. VR applied to gate R (see Supplementary Note 6). We expect the following scenario: When VR is changed toward negative values the charge carrier density n gets reduced locally underneath the gate and gets closer to the critical density nc at which superconductivity becomes suppressed.
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