Evidence for ans-wave superconducting gap in KxFe2−ySe

Min Xu

¹

,

Q. Q. Ge

²

,

Rui Peng

³

et al.

Fermiology, orbital order, orbital fluctuations, and Cooper pairing in iron-based superconductors

“…[37,38]. This result is consistent with the recent ARPES result which rules out d-wave pairing based on the mapping of the gap function on the electron pockets center around k = (0, 0, π) [39].…”

The orbital characters of low-energy electronic structure in iron-chalcogenide superconductor K x Fe2−y Se2

“…One of the two bands is dominated by the d xz and d yz orbitals, while the other one is dominated by the d xy orbital. The weak interactions between these two Fermi cylinders suggest that even if the superconducting order parameters on them have opposite signs, gap nodes would be absent [30,31]. Our results provide a foundation for the understanding and realistic modeling of K x Fe 2−y Se 2 .…”

Superconductivity at the border of electron localization and itinerancy

“…On the other hand, ARPES experiments have suggested that the superconducting gap is nodeless on the faint electron pocket near the G point 30,31 . This appears to favour an A 1g s x 2 y 2 wave pairing 30,31 . Further experiments are needed to settle which of the two possible pairing channels operates in the alkaline iron selenides.…”

“…This extreme overdoping in KFe 2 As 2 means that the system is far away from the Mott transition-anchoring point discussed here and should, therefore, have considerably reduced 29 . This is most readily understood in terms of a B 1g d x 2 À y 2 wave pairing 29 , although it may also arise from an A 1g s x 2 y 2 channel once the effect of two iron ions per unit cell is taken into account 30 . On the other hand, ARPES experiments have suggested that the superconducting gap is nodeless on the faint electron pocket near the G point 30,31 .…”

“…This is most readily understood in terms of a B 1g d x 2 À y 2 wave pairing 29 , although it may also arise from an A 1g s x 2 y 2 channel once the effect of two iron ions per unit cell is taken into account 30 . On the other hand, ARPES experiments have suggested that the superconducting gap is nodeless on the faint electron pocket near the G point 30,31 . This appears to favour an A 1g s x 2 y 2 wave pairing 30,31 .…”