Competing superconducting channels in iron pnictides from the strong coupling theory with biquadratic spin interactions. (13th October 2016)

• Record Type: Journal Article
• Authors: Yu, Rong; Nevidomskyy, Andriy H
• Is Part Of: Journal of physics. Volume 28:Number 49(2016)
• Publication Date: 2016-10-13
• Subjects: iron pnictides -- superconducting pairing -- biquadratic interaction; Condensed matter -- Periodicals; Matière condensée -- Périodiques; Vaste stoffen; Vloeistoffen; Natuurkunde; Electronic journals; Computer network resources; 530.4105
• DOI: 10.1088/0953-8984/28/49/495702
• Languages: English
• ISSNs: 0953-8984

Abstract

Abstract: We study the symmetry and strength of the superconducting pairing in a two-orbital t − J 1 − J 2 − K model for iron pnictides using the slave boson strong coupling approach. We show that the nearest-neighbor biquadratic interaction − K ( S → i ⋅ S → j ) 2 strongly affects the superconducting pairing phase diagram by promoting the d x 2 − y 2 B 1 g and the s x 2 + y 2 A 1 g channels. The resulting phase diagram consists of several competing pairing channels, including the isotropic s ± A 1 g channel, an anisotropic d x 2 − y 2 B 1 g channel, and two s + i d 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 s + i d and even pure d -wave pairing in the heavily electron- and hole-doped regimes. In addition, we identify a novel orbital- B 1 g pairing channel, which has a s -wave form factor but a B 1 g symmetry. 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 BaFe2 As2 and K-doped FeSe films.