Abstract
Conventional Cooper pairing arises from attractive interaction of electrons in the metallic bands. A recent experiment on Co-doped LiFeAs shows superconductivity in the insulating valence band, which is evolved from a metallic hole band upon doping. Here we examine this phenomenon by studying superconductivity in a three-orbital Hamiltonian relevant to the doped LiFeAs. We show explicitly that Cooper pairing of the insulating hole band requires a finite pairing interaction strength. For strong coupling, the superconductivity in the hole band is robust against the sink of the hole band below the Fermi level. Our theory predicts a substantial upward shift of the chemical potential in the superconducting transition for Co-doped LiFeAs.
- Received 12 March 2015
- Revised 7 April 2015
DOI:https://doi.org/10.1103/PhysRevB.91.161108
©2015 American Physical Society