Abstract
Recent angle-resolved spectroscopy in -based superconductors has indicated that the superconducting gap amplitude possesses remarkable anisotropy and/or a sign change on a small Fermi pocket around the point. It implies a possibility of an unconventional pairing state. Here we study the gap anisotropy in superconductivity mediated by inherent charge and quadrupole fluctuations in an extended Hubbard model, which includes intersite interaction between Bi and S atoms. The first-principles downfolded band structure is composed of Bi and S orbitals on a single layer. Evaluating the linearized gap equation, we find that the ferroic charge and quadrupole fluctuation driven by the intersite interaction leads to a fully gapped -wave pairing state, in which the gap amplitude has sizable anisotropy on the Fermi surface.
- Received 5 March 2017
DOI:https://doi.org/10.1103/PhysRevB.96.024513
©2017 American Physical Society