Signatures of chiral superconductivity in rhombohedral graphene

• 成果类型: Article
• 署名作者: Han, Tonghang; Lu, Zhengguang; Hadjri, Zach; Shi, Lihan; Wu, Zhenghan; Xu, Wei; Yao, Yuxuan; Cotten, Armel A.; Sedeh, Omid Sharifi; Weldeyesus, Henok; Yang, Jixiang; Seo, Junseok; Ye, Shenyong; Zhou, Muyang; Liu, Haoyang; Shi, Gang; Hua, Zhenqi; Watanabe, Kenji; Taniguchi, Takashi; Xiong, Peng; Zumbuehl, Dominik M.; Fu, Liang; Ju, Long
• 署名单位: Massachusetts Institute of Technology (MIT); State University System of Florida; Florida State University; University of Basel; National Institute for Materials Science; National Institute for Materials Science
• 刊物名称: Nature
• ISSN/ISSBN: 0028-2156
• DOI: 10.1038/s41586-025-09169-7
• 发表日期: 2025-07-17
• 关键词: spin; ferromagnetism; coexistence; breaking; symmetry; magnets; STATES; ORDER

摘要

Chiral superconductors are unconventional superconducting states that break time-reversal symmetry spontaneously and typically feature Cooper pairing at non-zero angular momentum. Such states may host Majorana fermions and provide an important platform for topological physics research and fault-tolerant quantum computing1, 2, 3, 4, 5, 6-7. Despite intensive search and prolonged studies of several candidate systems8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25-26, chiral superconductivity has remained elusive so far. Here we report the discovery of robust unconventional superconductivity in rhombohedral tetralayer and pentalayer graphene without moir & eacute; superlattice effects. We observed two superconducting states in the gate-induced flat conduction bands with Tc up to 300 mK and charge density ne down to 2.4 x 1011 cm-2 in five devices. Spontaneous time-reversal-symmetry breaking (TRSB) owing to orbital motion of the electron is found and several observations indicate the chiral nature of these superconducting states, including: (1) in the superconducting state, Rxx shows magnetic hysteresis in varying out-of-plane magnetic field B perpendicular to-absent from all other superconductors; (2) the superconducting states are robust against in-plane magnetic field and are developed within a spin-polarized and valley-polarized quarter-metal (QM) phase; (3) the normal states show anomalous Hall signals at zero magnetic field and magnetic hysteresis. We also observed a critical B perpendicular to of 1.4 T, higher than any graphene superconductivity, which indicates a strong-coupling superconductivity close to the Bardeen-Cooper-Schrieffer (BCS)-Bose-Einstein condensate (BEC) crossover27. Our observations establish a pure carbon material for the study of topological superconductivity, with the promise to explore Majorana modes and topological quantum computing.