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I will show that two-dimensional fermions with k2 and k4 dispersion undergo a first-order Stoner transition to a fully spin-polarized state despite that the spin susceptibility diverges at the critical point. I will then extend the analysis to systems with dispersions k2a and spin and valley isospin and show there is a cascade of instabilities into fractional-metal states with some electron bands fully depleted. I will discuss applications to Bernal bilayer graphene in a displacement field and 2D electron gases. I will also discuss superconductivity near an isospin ordering.

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Andrey Chubukov, University of Minnesota
Seminar Room 0.03, ETP
Contact: Simon Trebst