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Signatures of emergent interfacial superconductivity in 45-degree twisted van der Waals Cuprate Superconductors

ORAL

Abstract

We developed a cryogenic assembly technique to fabricate Josephson Junctions with an atomically sharp twisted interface between Bi2Sr2CaCu2O8+x crystals. Transport measurements probing the interface revealed a suppressed but finite critical current close to 45 degrees. Fraunhofer patterns revealed anomalous junction effective thickness, which can be explained by a theoretical analysis that incorporates the second harmonic in the Josephson Energy versus phase relation. We study the change of Fraunhofer patterns as we vary applied in-plane magnetic field direction, probing the current distribution in the Josephson junction. Our theoretical analysis supports the dominant second harmonic in our Josephson Junctions, indicating time-reversal broken interfacial superconductivity.

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Publication: https://arxiv.org/abs/2108.13455<br>Twisted interfaces between stacked van der Waals cuprate crystals enable tunable Josephson coupling between in-plane anisotropic superconducting order parameters. Employing a novel cryogenic assembly technique, we fabricate Josephson junctions with an atomically sharp twisted interface between Bi2Sr2CaCu2O8+x crystals. The Josephson critical current density sensitively depends on the twist angle, reaching the maximum value comparable to that of the intrinsic junctions at small twisting angles, and is suppressed by almost 2 orders of magnitude yet remains finite close to 45 degree twist angle. Through the observation of fractional Shapiro steps and the analysis of Fraunhofer patterns we show that the remaining superconducting coherence near 45 degree is due to the co-tunneling of Cooper pairs, a necessary ingredient for high-temperature topological superconductivity.

Presenters

  • Alex cui

    Harvard University

Authors

  • Alex cui

    Harvard University

  • Shu Yang Frank Zhao

    Harvard University

  • Pavel A Volkov

    Rutgers University

  • Jed Pixley

    Rutgers University

  • Nicola Poccia

    IFW Dresden

  • Philip Kim

    Harvard University

  • Genda Gu

    Brookhaven National Laboratory, Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, NY 11973, USA

  • Ruidan Zhong

    Shanghai Jiaotong University

  • Sangmin Lee

    Seoul National University

  • Hyobin Yoo

    Sogang University

  • Jules A Gardener

    Harvard CNS

  • Austin Akey

    Harvard CNS

  • Rebecca Engelke

    Harvard University

  • Yuval Ronen

    Harvard University

  • Marcel Franz

    University of British Columbia

  • Tarun Tummuru

    University of British Columbia

  • Stephan Plugge

    University of British Columbia