Title | Topological chiral superconductivity with spontaneous vortices and supercurrent in twisted bilayer graphene |
Publication Type | Journal Article |
Year of Publication | 2019 |
Authors | F. Wu |
Journal | Phys. Rev. B |
Volume | 99 |
Pagination | 195114 |
Date Published | MAY 8 |
Type of Article | Article |
ISSN | 2469-9950 |
Abstract | We study d-wave superconductivity in twisted bilayer graphene and reveal phenomena that arise due to the moire superlattice. In the d-wave pairing, the relative motion (RM) of two electrons in a Cooper pair can have either d + id or d - id symmetry with opposite angular momenta. Due to the enlarged moire superlattice, the center-of-mass motion (COMM) can also carry a finite angular momentum while preserving the moire periodicity. By matching the total angular momentum, which has contributions from both the RM and the COMM, Cooper pairs with d + id and d - id RMs are intrinsically coupled in a way such that the COMM associated with one of the RMs has a spontaneous vortex-antivortex lattice configuration. Another phenomenon is that the chiral d-wave state carries spontaneous bulk circulating supercurrent. The chiral d-wave superconductors are gapped and also topological as characterized by an integer Chern number. Nematic d-wave superconductors, which could be stabilized, for example, by uniaxial strain, are gapless with point nodes. |
DOI | 10.1103/PhysRevB.99.195114 |