Orbital-Selective Pairing and Nematic Order in the Iron-Based Superconductors*

The considerations of the orbital-selective Mott phase in the normal state [1,2] motivated the theoretical proposal for orbital-selective pairing [3]. The experimental evidence for the latter has come from both the iron pnictides [4] and iron selenides [5]. Motivated by the recent experiments, we theoretically study the role of the nematic order in the orbital-selective pairing within multi-orbital models for superconductivity driven by short-range magnetic exchange interactions. We consider several ways that characterize the nematicity in the Hamiltonian, and present systematic results on how the pairing-state competition [6], the orbital dependency of the intra-orbital pairing amplitudes, the pairing symmetry and the gap anisotropy depend on the nematicity.

[1] R. Yu and Q. Si, PRL 110, 146402 (2013); PRB 84, 235115 (2011).
[2] M. Yi et al., PRL 110, 067003 (2013).
[3] R. Yu, J.-X. Zhu and Q. Si, PRB 89, 024509 (2014).
[4] C. Zhang et al., Phys. Rev. Lett. 111, 207002 (2013).
[5] P. O. Sprau et al., Science 357, 75 (2017).
[6] E. M. Nica, R. Yu and Q. Si, Npj Quantum Materials 2, 24 (2017).