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 t−J1 −J2 −K model for iron pnictides using the salve boson mean-field theory. We show that the nearest-neighbor biquadratic interaction −K( Si · Sj ) 2 inflences the superconducting pairing phase diagram by promoting the d x 2 −y 2 B1g and the s x 2 +y 2 A1g channels. The resulting phase diagram consists of several competing pairing channels, including an isotropic s± A1g channel, an anisotropic d x 2 −y 2 B1g channel, and two s + id pairing channels. We have investigated the evolution of superconducting states with electron doping, and find that with the biquadratic interaction various pairing channels may dominate at different doping concentrations. We show that this is crucial in understanding the doping evolution of superconducting gap anisotropy observed in some angle resolved photoemission spectrum measurements.

Magnetic and structural properties of the iron oxychalcogenides La2O2Fe2OM2(MFreelon1, Yamani2, Swainson3 et al. 2019Phys. Rev. B11290View full textAdd to dashboardCite

“…Several spin Hamiltonians have been introduced in order to address the magnetic behavior of materials thought to be within strong coupling limit e.g. iron oxychalcogenides and iron alkaline selenides A 0.8 Fe 1.6 Se 2 → A 2 Fe 4 Se 5 (referred to as "245s" where A = Rb, Cs, K and Tl) [40][41][42][43]. Unlike the iron pnictides, the increased electron correlation of the iron chalcogenides and iron alkaline selenides leads to narrower iron bandwidths.…”