Orbital Selectivity in Electron Correlations and Superconducting Pairing of Iron-Based Superconductors

Abstract

Electron correlations play a central role in iron-based superconductors. In these systems, multiple Fe 3d-orbitals are active in the low-energy physics, and they are not all degenerate. For these reasons, the role of orbital-selective correlations has been an active topic in the study of the iron-based systems. In this article, we survey the recent developments on the subject. For the normal state, we emphasize the orbital-selective Mott physics that has been extensively studied, especially in the iron chalcogenides, in the case of electron filling n∼6. In addition, the interplay between orbital selectivity and electronic nematicity is addressed. For the superconducting state, we summarize the initial ideas for orbital-selective pairing and discuss the recent explosive activities along this direction. We close with some perspectives on several emerging topics. These include the evolution of the orbital-selective correlations, magnetic and nematic orders, and superconductivity as the electron filling factor is reduced from 6 to 5, as well as the interplay between electron correlations and topological band structure in iron-based superconductors.

Preferred Spin Excitations in the Bilayer Iron-Based Superconductor CaK(Fe0.96Ni0.04)4Liu1, Bourgès2, Sidis3 et al. 2022Phys. Rev. Lett.12130View full textAdd to dashboardCite

“…3(a)]. The universality of the c-axis preferred spin resonance supports the orbital-selective pairing in iron-pnictide superconductors [62,70,71]. The Cooper pairs might be favored by particular orbital orders, which are robustly coupled to the local spins of Fe in most systems even at high temperatures far above T c .…”

Preferred Spin Excitations in the Bilayer Iron-Based Superconductor CaK(Fe$_{0.96}$Ni$_{0.04}$)$_4$As$_4$ with Spin-Vortex Crystal Order

“…On the other hand, the c−axis component (M c ) is well preserved, leaving enough spectral weight to form the spin resonance below T c [Fig.3(a)]. The universality of c−axis preferred spin resonance supports the orbital-selective pairing in iron-pnictide superconductors[62,70,71]. The Cooper pairs might be favoured by particular orbital orders, which are robustly coupled to the local spins of Fe in most systems even at high temperatures far above T c .…”

Origin of insulating ferromagnetism in iron oxychalcogenide Ce$_2$O$_2$FeSe$_2$

“…Interestingly, at intermediate U/W and 0.21 J H /U 0.30, due to the strong competition between J H /U and U/W the system is in exotic OSMP-FM state with the selective localization of electrons on one orbital while other orbitals remain metallic with itinerant electrons. This state was extensively studied in recent literature [36,52,53] and will not be discussed here further. At both large U/W and J H /U , the system develops a gap and becomes Mott insulating, defining the MI-FM state of our main focus.…”