Description
In this talk, I will present an introductory discussion on the
multi-orbital physics in the iron-based superconductors. In
the normal state, this concerns the effect of electron
correlations [1]. I will describe how an orbital-selective Mott
phase anchors the orbital selectivity [2], which has been a
subject of extensive theoretical and experimental studies. In
the superconducting state, I will address how orbital
selectivity not only can influence the usual superconducting
properties (for instance, gap anisotropy) but also may give
rise to new types of orbital-selective superconducting state.
The latter is exemplified by a proposed ?s-tau3? pairing
state, which provides a natural understanding of some
seemingly contradictory properties observed in the iron-
chalcogenide superconductors [3].
[1] Q. Si, R. Yu and E. Abrahams, "High Temperature
Superconductivity in Iron Pnictides and Chalcogenides", Nat.
Rev. Mater. 1, 16017 (2016).
[2] R. Yu and Q. Si, "Orbital-selective Mott phase in
multiorbital models for iron pnictides and chalcogenides",
arXiv:1705.04541.
[3] E. M. Nica, R. Yu and Q. Si, "Orbital selective pairing and
superconductivity in iron selenides", Npj Quantum Materials,
in press; arXiv:1703.03170 (arXiv:1505.04170).
