Landau Levels in Bilayer Graphene under Pressure

Bilayer graphene in a magnetic field hosts various ordered phases near neutrality, built from 8 low-energy Landau levels labeled by orbital n=0,1, valley ξ=+,- and spin σ=↑,↓. Phase energies depend strongly on interactions and the variables magnetic field, interlayer bias, and pressure. We find the ground state as function of these variables using a Hartree-Fock treatment including the effects of metallic gates, layer separation, layer thickness. Gates screen long-range interactions, separation weakens intervalley interactions, and thickness weakens the Coulomb blockade between layers; these effects distort the phase diagram but do not change its topology. We find that pressure strengthens the noninteracting scale relative to the Coulomb energy, which drives phase transitions to occur at lower fields. This stabilizes two orbitally polarized states not yet predicted or observed, adding to previously-identified valley-, spin-, and partially polarized states.