Superconductivity and spin canting in spin-orbit-coupled trilayer graphene

• 成果类型: Article
• 署名作者: Patterson, Caitlin L.; Sheekey, Owen I.; Arp, Trevor B.; Holleis, Ludwig F. W.; Koh, Jin Ming; Choi, Youngjoon; Xie, Tian; Xu, Siyuan; Guo, Yi; Stoyanov, Hari; Redekop, Evgeny; Zhang, Canxun; Babikyan, Grigory; Gong, David; Zhou, Haoxin; Cheng, Xiang; Taniguchi, Takashi; Watanabe, Kenji; Huber, Martin E.; Jin, Chenhao; Lantagne-Hurtubise, Etienne; Alicea, Jason; Young, Andrea F.
• 署名单位: University of California System; University of California Santa Barbara; California Institute of Technology; Harvard University; University of California System; University of California Berkeley; National Institute for Materials Science; National Institute for Materials Science; Children's Hospital Colorado; University of Colorado System; University of Colorado Denver; University of Colorado Anschutz Medical Campus; California Institute of Technology; University of Sherbrooke; University of Sherbrooke; California Institute of Technology
• 刊物名称: Nature
• ISSN/ISSBN: 0028-3313
• DOI: 10.1038/s41586-025-08863-w
• 发表日期: 2025-05-15
• 关键词: insulator

摘要

Graphene and transition metal dichalcogenide flat-band systems show similar phase diagrams, replete with magnetic1, 2, 3, 4-5 and superconducting6, 7, 8, 9, 10-11 phases. An abiding question has been whether magnetic ordering competes with superconductivity or facilitates pairing. For example, recent studies of Bernal bilayer graphene in the presence of enhanced spin-orbit coupling show a substantial increase in the observed domain and critical temperature Tc of superconducting states12, 13-14; however, the mechanism for this enhancement remains unknown. Here we show that introducing spin-orbit coupling in rhombohedral trilayer graphene (RTG) by substrate proximity effect generates new superconducting pockets for both electron and hole doping, with maximal Tc approximate to 300 mK, which is three times larger than in RTG encapsulated by hexagonal boron nitride. Using local magnetometry, we show that superconductivity straddles a transition between a spin-canted state with a finite in-plane magnetic moment and a state with complete spin-valley locking. This transition is reproduced in our Hartree-Fock calculations, in which this transition is driven by the competition between spin-orbit coupling and the carrier-density-tuned Hund's interaction. Our experiment suggests that the enhancement of superconductivity by spin-orbit coupling is driven by a quantitative change in the canting angle rather than a change in the ground state symmetry. These results align with a recently proposed mechanism for the enhancement of superconductivity15, in which fluctuations in the spin-canting order contribute to the pairing interaction.