Stabilizing Fluctuating Spin-Triplet Superconductivity in Graphene via Induced Spin-Orbit Coupling

Jonathan B. Curtis, Nicholas R. Poniatowski, Yonglong Xie, Amir Yacoby, Eugene Demler, and Prineha Narang

Phys. Rev. Lett. 130, 196001 – Published 9 May 2023

Abstract

A recent experiment showed that a proximity-induced Ising spin-orbit coupling enhances the spin-triplet superconductivity in Bernal bilayer graphene. Here, we show that, due to the nearly perfect spin rotation symmetry of graphene, the fluctuations of the spin orientation of the triplet order parameter suppress the superconducting transition to nearly zero temperature. Our analysis shows that both an Ising spin-orbit coupling and an in-plane magnetic field can eliminate these low-lying fluctuations and can greatly enhance the transition temperature, consistent with the recent experiment. Our model also suggests the possible existence of a phase at small anisotropy and magnetic field which exhibits quasilong-range ordered spin-singlet charge $4 e$ superconductivity, even while the triplet $2 e$ superconducting order only exhibits short-ranged correlations. Finally, we discuss relevant experimental signatures.

Received 26 September 2022
Accepted 11 April 2023

DOI:https://doi.org/10.1103/PhysRevLett.130.196001

Physics Subject Headings (PhySH)

Spin-orbit coupling Spin-triplet pairing Superconducting fluctuations

Bilayer graphene Graphene

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Jonathan B. Curtis ^1,2,*, Nicholas R. Poniatowski², Yonglong Xie ², Amir Yacoby ², Eugene Demler³, and Prineha Narang^1,†

¹College of Letters and Science, University of California, Los Angeles, California 90095, USA
²Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
³Institute for Theoretical Physics, ETH Zürich, 8093 Zürich, Switzerland