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Twist-programmable superconductivity in spin-orbit coupled bilayer graphene

ORAL

Abstract

The concept of angle rotation control is not necessarily exclusive to moiré superlattices. It can also be employed to induce programmable symmetry-breaking perturbations for stabilizing desired correlated states. Here, we experimentally demonstrate 'moiréless' twist-tuning of superconductivity together with other correlated orders in Bernal bilayer graphene proximitized by tungsten diselenide. The precise alignment between the two materials systematically controls the strength of the induced Ising spin-orbit coupling (SOC), profoundly altering the phase diagram. As Ising SOC is increased, superconductivity onsets at a higher displacement field and features a higher critical temperature, reaching up to 0.5 K. Within the main superconducting dome and in the strong Ising SOC limit, we find an unusual phase transition characterized by a nematic redistribution of holes among trigonally warped Fermi pockets and enhanced resilience to in-plane magnetic fields. The behavior is well captured by our theoretical model emphasizing interband interactions. Moreover, we identify two additional superconducting regions, one of which descends from an inter-valley coherent normal state and exhibits a Pauli-limit violation ratio exceeding 40, among the highest for all known superconductors. Our results provide essential insights into ultra-clean graphene-based superconductors and underscore the potential of moiréless-twist engineering across various van der Waals heterostructures.

Publication: arXiv:2408.10335

Presenters

  • Yiran Zhang

    Harvard University, Caltech

Authors

  • Yiran Zhang

    Harvard University, Caltech

  • Gal Shavit

    Caltech

  • Huiyang Ma

    Florida State University

  • Youngjoon Han

    Caltech

  • Kenji Watanabe

    National Institute for Materials Science, NIMS, Research Center for Functional Materials, National Institute for Materials Science, Research Center for Electronic and Optical Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan, Research Center for Functional Materials, National Institute of Material Science, Tsukuba, Japan, National Institute of Materials Science, Advanced Materials Laboratory, National Institute for Materials Science

  • Takashi Taniguchi

    National Institute for Materials Science, International Center for Materials Nanoarchitectonics, National Institute for Materials Science, Research Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan, International Center for Materials Nanoarchitectonics, National Institute of Material Science, Tsukuba, Japan, Advanced Materials Laboratory, National Institute for Materials Science

  • David Hsieh

    Caltech

  • Cyprian K Lewandowski

    National High Magnetic Field Laboratory, Florida State University

  • Felix von Oppen

    Berlin

  • Yuval Oreg

    Weizmann Institute of Science

  • Stevan Nadj-Perge

    Caltech