RSS icon
Twitter icon
Facebook icon
Vimeo icon
YouTube icon

Topological chiral superconductivity with spontaneous vortices and supercurrent in twisted bilayer graphene

TitleTopological chiral superconductivity with spontaneous vortices and supercurrent in twisted bilayer graphene
Publication TypeJournal Article
Year of Publication2019
AuthorsF. Wu
JournalPhys. Rev. B
Volume99
Pagination195114
Date PublishedMAY 8
Type of ArticleArticle
ISSN2469-9950
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.

DOI10.1103/PhysRevB.99.195114