TY - JOUR
T1 - Landau level phases in bilayer graphene under pressure at charge neutrality
AU - Green, Brett R.
AU - Sofo, Jorge O.
N1 - Funding Information:
This material is based upon work supported by the National Science Foundation Graduate Research Fellowship Program under Grant No. DGE1255832. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author and do not necessarily reflect the views of the National Science Foundation. B.G. acknowledges training provided by the Computational Materials Education and Training (CoMET) NSF Research Traineeship (Grant No. DGE-1449785).
Publisher Copyright:
© 2020 American Physical Society. ©2020 American Physical Society.
PY - 2020/5/15
Y1 - 2020/5/15
N2 - Bilayer graphene in a magnetic field hosts a variety of ordered phases built from eight Landau levels close in energy to the neutrality point. These levels are characterized by orbital n=0,1, valley ζ=+,-, and spin σ=↑,↓; their relative energies depend strongly on the Coulomb interaction, magnetic field, and interlayer bias. We treat interactions at the Hartree-Fock level, including the effects of metallic gates, layer separation, spatial extent of the pz orbitals, all Slonczewski-Weiss-McClure tight-binding parameters, and pressure. We obtain the ground state as function of the applied magnetic field, bias, and pressure. The gates, layer separation, and extent of the pz orbitals weaken the Coulomb interaction at different length scales; these effects distort the phase diagram but do not change its topology. However, previously predicted continuous transitions become discontinuous when all tight-binding parameters are included nonperturbatively. We find that pressure increases the importance of the noninteracting scale with respect to the Coulomb energy, which drives phase transitions to occur at lower fields. This brings two orbitally polarized states not yet predicted or observed into the experimentally accessible region of the phase diagram, in addition to previously identified valley-polarized, spin-polarized, and partially orbitally polarized states.
AB - Bilayer graphene in a magnetic field hosts a variety of ordered phases built from eight Landau levels close in energy to the neutrality point. These levels are characterized by orbital n=0,1, valley ζ=+,-, and spin σ=↑,↓; their relative energies depend strongly on the Coulomb interaction, magnetic field, and interlayer bias. We treat interactions at the Hartree-Fock level, including the effects of metallic gates, layer separation, spatial extent of the pz orbitals, all Slonczewski-Weiss-McClure tight-binding parameters, and pressure. We obtain the ground state as function of the applied magnetic field, bias, and pressure. The gates, layer separation, and extent of the pz orbitals weaken the Coulomb interaction at different length scales; these effects distort the phase diagram but do not change its topology. However, previously predicted continuous transitions become discontinuous when all tight-binding parameters are included nonperturbatively. We find that pressure increases the importance of the noninteracting scale with respect to the Coulomb energy, which drives phase transitions to occur at lower fields. This brings two orbitally polarized states not yet predicted or observed into the experimentally accessible region of the phase diagram, in addition to previously identified valley-polarized, spin-polarized, and partially orbitally polarized states.
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U2 - 10.1103/PhysRevB.101.195432
DO - 10.1103/PhysRevB.101.195432
M3 - Article
AN - SCOPUS:85085988682
SN - 2469-9950
VL - 101
JO - Physical Review B
JF - Physical Review B
IS - 19
M1 - 195432
ER -