title: Competing superconducting channels in iron pnictides from the strong coupling theory with biquadratic spin interactions.
abstract: We study the symmetry and strength of the superconducting pairing in a two-orbital [Formula: see text] model for iron pnictides using the slave boson strong coupling approach. We show that the nearest-neighbor biquadratic interaction [Formula: see text] strongly affects the superconducting pairing phase diagram by promoting the [Formula: see text] B1gand the [Formula: see text] A1gchannels. The resulting phase diagram consists of several competing pairing channels, including the isotropic [Formula: see text] A1gchannel, an anisotropic [Formula: see text] B1gchannel, and two [Formula: see text] pairing channels. We have investigated the evolution of superconducting states with electron doping, and find that the biquadratic interaction plays a crucial role in stabilizing the [Formula: see text] and even pure d-wave pairing in the heavily electron- and hole-doped regimes. In addition, we identify a novel orbital-B1gpairing channel, which has a s-wave form factor but a B1gsymmetry. This channel has a comparable pairing amplitude to the d-wave pairing, and may strongly influence the superconducting gap anisotropy of the system in the overdoped regime. These findings are crucial in understanding the doping evolution of the superconducting gap anisotropy observed by angle resolved photoemission spectroscopy in the iron pnictides and iron chalcogenides, including the heavily K-doped BaFe2As2and K-doped FeSe films.
authors.affiliation: Department of Physics and Beijing Key Laboratory of Opto-electronic Functional Materials & Micro-nano Devices, Renmin University of China, Beijing 100872, People's Republic of China. Department of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, China and Collaborative Innovation Center of Advanced Microstructures, Nanjing 210093, People's Republic of China.
authors.forename: Rong
authors.initials: R
authors.lastname: Yu
authors.forename: Andriy H
authors.initials: AH
authors.lastname: Nevidomskyy