Unconventional discontinuous transitions in isospin systems
Abstract
We show that two-dimensional fermions with dispersion $k^2$ or $k^4$ undergo a first-order Stoner transition to a fully spin-polarized state despite that the spin susceptibility diverges at the critical point. We extend our analysis to systems with dispersion $k^{2\alpha}$ and spin and valley isospin and show that there is a cascade of instabilities into fractional-metal states with some electron bands fully depleted; narrow intermediate ranges of partially-depleted bands exist for $\alpha<1$ or $\alpha > 2$. The susceptibility becomes large near each transition. We discuss applications to biased bilayer and tri-layer graphene and moiré systems.
- Publication:
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arXiv e-prints
- Pub Date:
- June 2024
- DOI:
- 10.48550/arXiv.2406.04415
- arXiv:
- arXiv:2406.04415
- Bibcode:
- 2024arXiv240604415R
- Keywords:
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- Condensed Matter - Strongly Correlated Electrons
- E-Print:
- 6 pages, 4 figures