Berezinskii-Kosterlitz-Thouless transition and anomalous metallic phase in a hybrid Josephson junction array

C. G. L. Bøttcher; F. Nichele; J. Shabani; C. J. Palmstrøm; C. M. Marcus

doi:10.1103/PhysRevB.110.L180502

Letter

Berezinskii-Kosterlitz-Thouless transition and anomalous metallic phase in a hybrid Josephson junction array

C. G. L. Bøttcher ^1,*, F. Nichele ^1,†, J. Shabani ^2,‡, C. J. Palmstrøm ^2,3,4, and C. M. Marcus ¹

¹Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, 2100 Copenhagen, Denmark
²California NanoSystems Institute, University of California, Santa Barbara, California 93106, USA
³Department of Electrical Engineering, University of California, Santa Barbara, California 93106, USA
⁴Materials Department, University of California, Santa Barbara, California 93106, USA

^*Contact author: charlotte.boettcher@stanford.edu; Present address: Department of Applied Physics, Stanford University, Stanford, California 94305, USA.
^†Present address: IBM Research Laboratory, Zürich, Zürich, Switzerland.
^‡Present address: New York University, New York, New York 10003, USA.

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Phys. Rev. B 110, L180502 – Published 5 November, 2024

DOI: https://doi.org/10.1103/PhysRevB.110.L180502

Abstract

We investigate the Berezinskii-Kosterlitz-Thouless (BKT) transition in a semiconductor-superconductor two-dimensional Josephson junction array. Tuned by an electrostatic top gate, the system exhibits separate superconducting (S), anomalous metal (M*), and insulating (I) phases, bordered by separatrices of the temperature-dependent sheet resistance $R_{s}$ . We find that the gate-dependent BKT transition temperature falls to zero at the S-M* boundary, suggesting incomplete vortex-antivortex pairing in the M* phase. In the S phase, $R_{s}$ is roughly proportional to the perpendicular magnetic field at the BKT transition, as expected, while in the M* phase, $R_{s}$ deviates from its zero-field value as a power law in the field with exponent close to 1/2 at low temperature. An in-plane magnetic field eliminates the M* phase, leaving a small scaling exponent at the S-I boundary, which we interpret as a remnant of the incipient M* phase.

Physical Review B

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Berezinskii-Kosterlitz-Thouless transition and anomalous metallic phase in a hybrid Josephson junction array

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Berezinskii-Kosterlitz-Thouless transition and anomalous metallic phase in a hybrid Josephson junction array

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