Article

# Robustness of s-Wave Pairing in Electron-Overdoped A1-yFe2-xSe2 (A=K, Cs)

Physical Review X 09/2011; 1(1). DOI: 10.1103/PhysRevX.1.011009
Source: arXiv

ABSTRACT Using self-consistent mean-field and functional renormalization-group approaches, we show that s-wave pairing symmetry is robust in the heavily electron-doped iron chalcogenides AFe2-xSe2, where A=K, Cs. Recent neutron scattering experiments suggest that the effective nearest-neighbor spin exchange may be ferromagnetic in chalcogenides. This is different from the iron pnictides, where the nearest-neighbor magnetic exchange coupling is believed to be antiferromagnetic and leads to strong competition between s-wave and d-wave pairing in the electron-overdoped region. Our finding of a robust s-wave pairing in (K, Cs)Fe2-xSe2 differs from the d-wave pairing result obtained by other theories where nonlocal bare interaction terms and the next-to-nearest-neighbor J2 term are underestimated. Detecting the pairing symmetry in (K, Cs)Fe2-xSe2 may hence provide important insights regarding the mechanism of superconducting pairing in iron-based superconductors.

Download full-text

### Full-text

Available from: Ronny Thomale, Jun 18, 2015
0 Followers
·
79 Views
• Source
##### Article: Magnetism and its microscopic origin in iron-based high-temperature superconductors
[Hide abstract]
ABSTRACT: High-temperature superconductivity in the iron-based materials emerges from, or sometimes coexists with, their metallic or insulating parent compound states. This is surprising since these undoped states display dramatically different antiferromagnetic (AF) spin arrangements and N$\rm \acute{e}$el temperatures. Although there is general consensus that magnetic interactions are important for superconductivity, much is still unknown concerning the microscopic origin of the magnetic states. In this review, progress in this area is summarized, focusing on recent experimental and theoretical results and discussing their microscopic implications. It is concluded that the parent compounds are in a state that is more complex than implied by a simple Fermi surface nesting scenario, and a dual description including both itinerant and localized degrees of freedom is needed to properly describe these fascinating materials.
Nature Physics 09/2012; 8(10). DOI:10.1038/nphys2438 · 20.60 Impact Factor
• Source
##### Article: The magnetic moment enigma in Fe-based high temperature superconductors
[Hide abstract]
ABSTRACT: The determination of the most appropriate starting point for the theoretical description of Fe-based materials hosting high temperature superconductivity remains among the most important unsolved problem in this relatively new field. Most of the work to date has focused on the pnictides, with LaFeAsO, BaFe2As2 and LiFeAs being representative parent compounds of three families known as 1111, 122 and 111, respectively. This Topic Review examines recent progress in this area, with particular emphasis on the implication of experimental data which have provided evidence for the presence of electron itinerancy and the detection of local spin moments. In light of the results presented, the necessity of a theoretical framework contemplating the presence and the interplay between itinerant electrons and large spin moments is discussed. It is argued that the physics at the heart of the macroscopic properties of pnictides Fe-based high temperature superconductors appears to be far more complex and interesting than initially predicted.
Journal of Physics Condensed Matter 10/2014; 26(47). DOI:10.1088/0953-8984/26/47/473202 · 2.22 Impact Factor
• Source
##### Article: Possible nodal superconducting gap and Lifshitz transition in heavily hole-doped Ba0.1K0.9Fe2As2
[Hide abstract]
ABSTRACT: We performed a high energy resolution ARPES investigation of over-doped Ba0.1K0.9Fe2As2 with T_c= 9 K. The Fermi surface topology of this material is similar to that of KFe2As2 and differs from that of slightly less doped Ba0.3K0.7Fe2As2, implying that a Lifshitz transition occurred between x=0.7 and x=0.9. Albeit for a vertical node found at the tip of the emerging off-M-centered Fermi surface pocket lobes, the superconducting gap structure is similar to that of Ba0.3K0.7Fe2As2, suggesting that the paring interaction is not driven by the Fermi surface topology.
Physical Review B 08/2013; 88(22). DOI:10.1103/PhysRevB.88.220508 · 3.66 Impact Factor