Year: 2026
Type: preprint
Abstract: Electron doped rhombohedral multilayer graphene at high displacement field features an exceptionally flat band minimum with near-ideal quantum geometry. Experiments in this regime observe the formation of a 'quarter metal,' in which the electron liquid condenses into a single spin- and valley flavor. Remarkably, recent experiments have found a zero resistance state in the same region of the density- and displacement-field-tuned parameter space, attributed to the formation of a chiral superconductor from an orbitally ferromagnetic normal state. Here, we use nanoSQUID-on-tip magnetometry to map the orbital magnetization of electron-doped rhombohedral graphene devices ranging in thickness between 3 and 15 layers. Magnetization within the quarter metal phases peaks at finite density, consistent with concentration of the Berry curvature in a finite-momentum 'ring of fire'. Correlating transport and local magnetometry data in a superconducting tetralayer sample reveals a finite orbital ferromagnetic moment, providing direct evidence of valley polarization in the superconducting ground state. We further show that widely observed stochastic switching of the resistivity in both metallic and superconducting regimes arises from a density-tuned sign change in the valley-resolved total magnetic moment. This leads to the formation of metastable magnetic domains under typical gate control sequences and can also be harnessed for electric-field controlled switching of the magnetization across the entire device. Finally, high resolution measurements of the magnetization across a superconducting transition allow us to put an upper bound on the 'condensation magnetization' of 0.1 Bohr magneton per carrier, placing a strong quantitative restriction on theoretical models for ferromagnetic superconductivity.
Source: arXiv (Cornell University)
Authors: Sheekey, Owen I., Arp, Trevor B., Foutty, Benjamin A., Zhang, Ruoxi, Tan, Tixuan, Holleis, Ludwig F. W., Guo, Yi, Kalantre, Sandesh S., Zhang, Canxun, Zakharyan, Mark, Gong, David, Keough, Aidan, Choi, Youngjoon, Choi, Ysun, Xu, Siyuan, Xie, Tian, Alexander, Ben Hodder, Hocking, Marisa, Cao, Qingrui, Huber, Martin E., Taniguchi, Takashi, Watanabe, Kenji, Jin, Chenhao, Lantagne-Hurtubise, Etienne, Sharpe, Aaron, Devakul, Trithep, Young, Andrea F.
Language: English
Subfield: Materials Chemistry
Field: Materials Science
Domain: Physical Sciences
Open Access status: green
Funders: National Science Foundation, U.S. Department of Defense, U.S. Department of Energy, W. M. Keck Foundation, Gordon and Betty Moore Foundation, Université de Sherbrooke, Ministry of Education, Culture, Sports, Science and Technology, Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung, Office of Science, University of California, Santa Barbara, Multidisciplinary University Research Initiative, Natural Sciences and Engineering Research Council of Canada, Japan Society for the Promotion of Science, Division of Materials Research, Division of Electrical, Communications and Cyber Systems, Basic Energy Sciences
Awards: G1229526393, G1286251239, G1333989588, G1502681674, G2371548206, NNCI: nano@stanford, G2442584775, G2521557779, G303061748, NNCI: Stanford University - SNSF, SNF, MAF, EMF, G4089419421, G4162329948, G4264918310, G4399378207, G453897845, G4654690619, G4806815962, G495301720, G498139845, G501274426, G533464158, G5473946529, G5570207115, G5975534213, G6550344761, G6692005437, G7283024673, G7428312516, David Goldhaber-Gordon Experimental Investigator Award, Enabling Quantum Leap: Q-AMASE-i: Quantum Foundry at UCSB, G8035528278, G8065195062, Spectroscopy, Thermodynamics, and Thermal Transport of Superconductors in Multilayer Rhombohedral Graphene, G8382000481, G898758523, G9001001347, G911061179
OpenAlex ID: W7162750366