2018/05/31 by Hiroki Isobe, Noah F. Q. Yuan, Liang Fu · 1 citation
Physics and Astronomy · #cond-mat.str-el #cond-mat.supr-con
paper · pdf · doi:10.1103/physrevx.8.041041
published as Phys. Rev. X 8, 041041 (2018) · 15 pages, 12 figures; updated discussion and analysis on density wave states
arxiv created 2018/07/06 · arxiv updated 2018/12/10
We study electronic ordering instabilities of twisted bilayer graphene with n=2 electrons per supercell, where correlated insulator state and superconductivity are recently observed. Motivated by the Fermi surface nesting and the proximity to Van Hove singularity, we introduce a hot-spot model to study the effect of various electron interactions systematically. Using renormalization group method, we find d/p-wave superconductivity and charge/spin density wave emerge as the two types of leading instabilities driven by Coulomb repulsion. The density wave state has a gapped energy spectrum at n=2 and yields a single doubly-degenerate pocket upon doping to n>2. The intertwinement of density wave and superconductivity and the quasiparticle spectrum in the density wave state are consistent with experimental observations.