In moir\'e graphene systems, electronic interactions lift spin and valley degeneracies, leading to symmetry-broken ground states. In helical trilayer graphene (HTG), we uncover a distinct interaction-driven mechanism in which the roles of sublattice-polarized valence and conduction bands are cyclically reversed. Using scanning nano-SQUID magnetometry, we detect a series of sharp magnetic signatures consistent with seesaw-like transitions, where occupied and unoccupied valence and conduction bands interchange repeatedly with doping, accompanied by a novel form of magnetic hysteresis. These transitions occur entirely within metallic regimes and leave only weak fingerprints in transport measurements. Self-consistent Hartree-Fock calculations reveal that interactions reorganize all eight low-energy flat bands, driving abrupt changes in orbital magnetization. Our results establish HTG as the first system where electronic interactions provide doping-controlled access to all three internal degrees of freedom - spin, valley, and sublattice - introducing a new class of correlated phase transitions.
@article{arxiv.2603.21973,
title = {Electrically controllable valence-conduction band reversals in helical trilayer graphene},
author = {Matan Bocarsly and Indranil Roy and Weifeng Zhi and Li-Qiao Xia and Aviram Uri and Yves H. Kwan and Aaron Sharpe and Matan Uzan and Yuri Myasoedov and Kenji Watanabe and Takashi Taniguchi and Trithep Devakul and Pablo Jarillo-Herrero and Eli Zeldov},
journal= {arXiv preprint arXiv:2603.21973},
year = {2026}
}