Superconductivity and magnetism in the surface states of ABC-stacked multilayer graphene

Abstract

ABC-stacked multilayer graphene (ABC-MLG) exhibits topological surface flat bands with a divergent density of states, leading to many-body instabilities at charge neutrality. Here, we explore electronic ordering within a mean-field approach with full generic treatment of all spin-isotropic, two-site charge density and spin interactions up to next-nearest-neighbor (NNN) sites. We find that surface superconductivity and magnetism are significantly enhanced over bulk values. We find spin-singlet s wave and unconventional NNN bond spin-triplet f wave to be the dominant superconducting pairing symmetries, both with a full energy gap. By establishing the existence of ferromagnetic intrasublattice interaction (J2<0) we conclude that the f-wave state is favored in ABC-MLG, in sharp contrast to bulk ABC-graphite where chiral d- or p-wave states, together with s-wave states, display stronger ordering tendencies albeit not achievable at charge neutrality. We trace this distinctive surface behavior to the strong sublattice polarization of the surface flat bands. We also find competing ferrimagnetic order, fully consistent with density functional theory (DFT) calculations. The magnetic order interpolates between sublattice ferromagnetism and antiferromagnetism, but only with the ratio of the sublattice magnetic moments (R) being insensitive to the DFT exchange correlation functional. We finally establish the full phase diagram by constraining the interactions to the R value identified by DFT. We find f-wave superconductivity being favored for all weak to moderately strong couplings J2 and as long as J2 is a sufficiently large part of the full interaction mix. Gating ABC-MLG away from charge neutrality further enhances the f-wave state over the ferrimagnetic state, establishing ABC-MLG as a strong candidate for f-wave superconductivity.

• author: Awoga, Oladunjoye A. ; Löthman, Tomas and Black-Schaffer, Annica M.
• organization: LTH Profile Area: Nanoscience and Semiconductor Technology; NanoLund: Centre for Nanoscience; Department of Astronomy and Theoretical Physics - Has been reorganised
• publishing date: 2023-10-01
• type: Contribution to journal
• publication status: published
• subject: Condensed Matter Physics
• in: Physical Review B
• volume: 108
• issue: 14
• article number: 144504
• pages: 23 pages
• publisher: American Physical Society
• external identifiers: scopus:85177612889
• ISSN: 2469-9950
• DOI: 10.1103/PhysRevB.108.144504
• language: English
• LU publication?: yes
• additional info: Funding Information: We thank S. Nahas for useful discussions on the DFT calculations and C. Bena for general discussions. We acknowledge financial support from the Swedish Research Council (Vetenskapsrådet Grant No. 2018-03488) and the Knut and Alice Wallenberg Foundation through the Wallenberg Academy Fellows program, as well as the EU-COST Action CA-21144 Superqumap. Simulations were enabled by resources provided by the Swedish National Infrastructure for Computing (SNIC) at the Uppsala Multidisciplinary Center for Advanced Computational Science (UPPMAX), partially funded by the Swedish Research Council through Grant No. 2018-05973. In addition, O.A.A. acknowledges funding from NanoLund. Publisher Copyright: © 2023 authors. Published by the American Physical Society. Published by the American Physical Society under the terms of the "https://creativecommons.org/licenses/by/4.0/"Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Funded by "https://www.kb.se/samverkan-och-utveckling/oppen-tillgang-och-bibsamkonsortiet/bibsamkonsortiet.html"Bibsam.
• id: 64952f09-38d1-4978-924a-2cd3b9e83514
• date added to LUP: 2023-12-04 16:40:57
• date last changed: 2024-04-17 12:59:31