0-pi Juxtaposed Interference Patterns in FeSe/FeSe van der Waals Josephson Junctions

ORAL

Abstract

Recently, van der Waals (vdW) Josephson junctions (JJs) made of two thin flakes of Fe(Te,Se) have been fabricated to reveal the spontaneous time-reversal symmetry breaking in Fe(Te,Se) from a new angle [1]. Here, we investigated the superconducting state of FeSe by fabricating vdW JJ made of FeSe thin flakes, where there is nematicity and fewer impurities compared to Fe(Te,Se). Instead of a typical JJ Fraunhofer interference pattern that is symmetric with respect to DC current bias, we observed 0-junction behavior with positive current bias and pi-junction behavior with negative current bias. Accompanying the juxtaposed Fraunhofer pattern is a superconducting diode effect with maximum efficiency at zero field and symmetric field dependence with multiple sign changes. The implications of our results on spontaneous time-reversal symmetry breaking and superconducting pairing are discussed.

[1] G. Qiu*, H.-Y. Yang* (co-first author), L. Hu, H. Zhang, CY. Chen, Y. Lyu, C. Eckberg, P. Deng, S. Krylyuk, A.V. Davydov, R. Zhang, and K. L. Wang, "Emergent ferromagnetism with superconductivity in Fe(Te,Se) van der Waals Josephson junctions", Nat. Commun. 14, 6691 (2023)

* The work at Sandia is supported by a LDRD project. SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525.

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Presenters

  • Hung-Yu Yang

    University of California, Los Angeles

Authors

  • Hung-Yu Yang

    University of California, Los Angeles

  • Joseph J Cuozzo

    Sandia National Laboratories

  • Gang Qiu

    University of Minnesota

  • Ting-Hsun Yang

    UCLA, University of California, Los Angeles

  • Anand J Bokka

    University of California, Los Angeles

  • Abdullah Alrasheed

    University of California, Los Angeles

  • Yanfeng Lyu

    University of Houston

  • Kang-Lung Wang

    University of California, Los Angeles, UCLA