Correlated Hofstadter spectrum and flavour phase diagram in magic-angle twisted bilayer graphene
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- Stanford University, CA (United States)
- SLAC National Accelerator Lab., Menlo Park, CA (United States)
- National Institute for Material Science, Tsukuba (Japan)
- University of Illinois at Urbana-Champaign, IL (United States)
- Stanford University, CA (United States); SLAC National Accelerator Lab., Menlo Park, CA (United States)
In magic-angle twisted bilayer graphene, the moiré superlattice potential gives rise to narrow electronic bands that support a multitude of many-body quantum phases. Further richness arises in the presence of a perpendicular magnetic field, where the interplay between moiré and magnetic length scales leads to fractal Hofstadter subbands. In this strongly correlated Hofstadter platform, multiple experiments have identified gapped topological and correlated states, but little is known about the phase transitions between them in the intervening compressible regimes. Here we simultaneously unveil sequences of broken-symmetry Chern insulators and resolve sharp phase transitions between competing states with different topological quantum numbers and different occupations of the spin-valley flavour. Our measurements determine the energy spectrum of interacting Hofstadter subbands in magic-angle twisted bilayer graphene and map out the phase diagram of flavour occupancy. In addition, we observe full lifting of the degeneracy of the zeroth Landau levels together with level crossings, indicating moiré valley splitting. We propose a unified flavour polarization mechanism to understand the intricate interplay of topology, interactions and symmetry breaking as a function of density and applied magnetic field in this system.
- Research Organization:
- Stanford Univ., CA (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), Basic Energy Sciences (BES); Stanford University Terman Fellowship; Sloan Foundation Fellowship; MEXT, Japan; JSPS KAKENHI; Marvin Chodorow Postdoctoral Fellowship; Gordon and Betty Moore Foundation; National Science Foundation (NSF)
- Grant/Contract Number:
- AC02-76SF00515; SC0021238; JPMXP0112101001; JP20H00354; GBMF 4302; GBMF 8686; DMR-2111379; ECCS-2026822
- OSTI ID:
- 1878544
- Journal Information:
- Nature Physics, Vol. 18, Issue 7; ISSN 1745-2473
- Publisher:
- Nature Publishing Group (NPG)Copyright Statement
- Country of Publication:
- United States
- Language:
- English
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