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We study symmetry-broken phases in twisted bilayer graphene at small filling above charge neutrality and at Van Hove filling. We argue that the Landau functionals for the particle-hole order parameters at these fillings both have an approximate SU(4) symmetry, but differ in the sign of quartic terms. We determine the order parameter manifold of the ground state and analyze its excitations. For small fillings, we find a strong 1st-order transition to an SU(3)$otimes$U(1) manifold of orders that break spin-valley symmetry and induce a 3-1 splitting of fermionic excitations. For Van Hove filling, we find a weak 1st-order transition to an SO(4)$otimes$U(1) manifold of orders that preserves the two-fold band degeneracy. We discuss the effect of particle-hole orders on superconductivity and compare with strong-coupling approaches.
Motivated by recent low-temperature magnetoresistance measurements in twisted bilayer graphene aligned with hexagonal Boron Nitride substrate, we perform a systematic study of possible symmetry breaking orders in this device at a filling of two elect
Experiments on graphene bilayers, where the top layer is rotated with respect to the one below, have displayed insulating behavior when the moire bands are partially filled. We calculate the charge distributions in these phases, and estimate the excitation gaps.
We present a tight-binding calculation of a twisted bilayer graphene at magic angle $thetasim 1.08^circ$, allowing for full, in- and out-of-plane, relaxation of the atomic positions. The resulting band structure displays as usual four narrow mini ban
Refined infrared magnetotransmission experiments have been performed in magnetic fields B up to 35 T on a series of multilayer epitaxial graphene samples. Following the main optical transition involving the n=0 Landau level (LL), we observe a new abs
Recently twisted bilayer graphene (t-BLG) emerges as a new strongly correlated physical platform near a magic twist angle, which hosts many exciting phenomena such as the Mott-like insulating phases, unconventional superconducting behavior and emerge