Orbital-selective correlations and superconductivity in the nematic FeSe*

The interplay between electronic orders, orbital-selective electronic correlations and associated superconductivity, has played a central role in the physics of emergent phases and unconventional superconductivity. This interplay has been found to be particularly pronounced in recently discovered iron-based superconductors. Motivated by the recent low-temperature experiments on iron selenide (FeSe), we theoretically study the electronic correlation effects and emerging superconductivity in a multiorbital model for this compound. We propose that the combination of various bond nematic orders with the ferro-orbital order can give rise to a surprisingly large orbital selectivity among the Fe-3d t_2g orbitals in the normal state. This enhanced orbital selectivity is also reflected in the superconducting pairing amplitudes, which gives rise to a large gap anisotropy on the Fermi surface. Our results naturally explain the seemingly unusual observation of strong orbital selectivity and related unconventional superconductivity in the nematic phase of FeSe, thereby providing new insight into the nature of both the nematic order and the iron-based superconductivity in general.