Theory of electron correlation and orbital selectivity in Fe-based superconductors

It has been recognized that the electron correlation plays a crucial role in understanding the properties of the iron-based superconductors [1]. In this talk I will review recent theoretical progresses on the study of the electron correlations in iron-based superconductors [2-5]. I show that not only are the iron-based superconductors close to a Mott localization, but the multi-orbital nature of these systems can accommodate a novel orbital-selective Mott phase, in which some orbital is Mott localized while the others are still itinerant. The orbital-selective Mott phase anchors the understanding of the strong orbital selectivity in the iron-based superconductors, which has been extensively studied both experimentally and theoretically [5,6]. Using a U(1) slave-spin theory [2,7], I discuss the materials-specific aspects of the orbital-selective electron correlation in several iron selenides and iron pnictides and, furthermore, address its connection to the nematicity in these systems.

[1] Q. Si, R. Yu and E. Abrahams, Nature Rev. Mater. 1, 16017 (2016).
[2] R. Yu and Q. Si, Phys. Rev. B 96, 125110 (2017).
[3] R. Yu, and Q. Si, Phys. Rev. B 84, 235115 (2011).
[4] R. Yu, J.-X. Zhu, and Q. Si, Phys. Rev. Lett. 106, 186401 (2011).
[5] R. Yu and Q. Si, Phys. Rev. Lett. 110, 146402 (2013).
[6] M. Yi, et al., Phys. Rev. Lett. 110, 067003 (2013);
M. Yi, et al., Nat. Commun. 6, 7777 (2015).
[7] R. Yu and Q. Si, Phys. Rev. B 86, 085104 (2012).