Weak-coupling theory of half-metals and other fractional metallic phases in biased doped Bernal bilayer graphene
Abstract
The paper presents a theoretical study of many-body electronic phases in doped and electrically biased Bernal-stacked (AB) bilayer graphene. We develop a variational mean-field theory with no fitted parameters. For the electron-electron interaction, we employ a parameter-free random-phase approximation to model the short-range screened Coulomb repulsion. The remaining long-range Coulomb potential energy is dictated by the geometry of the sample, behaving as a parallel-plate capacitor. We formulate the theory directly in terms of the experimentally controlled displacement field frak D rather than the interaction-renormalized interlayer potential difference. It makes our theory better suited for direct comparison with experiment. The resulting phase diagram is quite rich. It hosts several fractional-metal states connected by first- and second-order transitions. At higher bias and doping, three distinct fractional metallic states emerge. We classify these phases by the number of doped sectors and the symmetry of the order parameters. Our results - obtained without any parameter fitting - reproduce key qualitative and quantitative features of recent experiments. This includes the energy scale associated with the loss of fractional metallic order. At lower bias and doping, the model stabilizes a broad spectrum of fractional-metal phases with more exotic symmetry-breaking patterns. This suggests that further experimental exploration of the latter regime is warranted.
Related
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- Stability, Collective Modes, and Quasiparticle-Phonon Coupling of Metallic Wigner Crystals in Rhombohedral Graphene
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- Composite Fermion Theory of Fractional Chern Insulators in Rhombohedral Graphene
BibTeX
@misc{zhitov2026weakcoupling,
title = {{Weak-coupling theory of half-metals and other fractional metallic phases in biased doped Bernal bilayer graphene}},
author = {D. V. Zhitov and A. V. Rozhkov and A. O. Sboychakov and A. L. Rakhmanov},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.03679},
eprint = {2609.03679},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.03679},
}
RIS
TY - UNPB
TI - Weak-coupling theory of half-metals and other fractional metallic phases in biased doped Bernal bilayer graphene
AU - D. V. Zhitov
AU - A. V. Rozhkov
AU - A. O. Sboychakov
AU - A. L. Rakhmanov
PY - 2026
DA - 2026/09/03
PB - arXiv
DO - 10.48550/arxiv.2609.03679
UR - https://arxiv.org/abs/2609.03679
AB - The paper presents a theoretical study of many-body electronic phases in doped and electrically biased Bernal-stacked (AB) bilayer graphene. We develop a variational mean-field theory with no fitted parameters. For the electron-electron interaction, we employ a parameter-free random-phase approximation to model the short-range screened Coulomb repulsion. The remaining long-range Coulomb potential energy is dictated by the geometry of the sample, behaving as a parallel-plate capacitor. We formulate the theory directly in terms of the experimentally controlled displacement field frak D rather than the interaction-renormalized interlayer potential difference. It makes our theory better suited for direct comparison with experiment. The resulting phase diagram is quite rich. It hosts several fractional-metal states connected by first- and second-order transitions. At higher bias and doping, three distinct fractional metallic states emerge. We classify these phases by the number of doped sectors and the symmetry of the order parameters. Our results - obtained without any parameter fitting - reproduce key qualitative and quantitative features of recent experiments. This includes the energy scale associated with the loss of fractional metallic order. At lower bias and doping, the model stabilizes a broad spectrum of fractional-metal phases with more exotic symmetry-breaking patterns. This suggests that further experimental exploration of the latter regime is warranted.
ER -