Abstract
Motivated by the recent discovery of superconductivity in the iron-based ladder compound under high pressure, we derive low-energy effective Hamiltonians from first principles. We show that the complex band structure around the Fermi level is represented only by the Fe (mixed with ) and orbitals. The characteristic band degeneracy allows us to construct a four-band model with the band unfolding approach. We also estimate the interaction parameters and show that the system is more correlated than the 1111 family of iron-based superconductors. Provided the superconductivity is mediated by spin fluctuations, the -like band plays an essential role, and the gap function changes its sign between the Fermi surface around the point and that around the Brillouin-zone boundary.
- Received 10 June 2015
DOI:https://doi.org/10.1103/PhysRevB.92.054515
©2015 American Physical Society