scholarly journals Possible high-Tcsuperconductivity mediated by antiferromagnetic spin fluctuations in systems with Fermi surface pockets

2001 ◽  
Vol 64 (2) ◽  
Author(s):  
Kazuhiko Kuroki ◽  
Ryotaro Arita
Keyword(s):  
Fermi Surface ◽  
Spin Fluctuations ◽  
Antiferromagnetic Spin

IMPACT OF THE ORDER PARAMETER SYMMETRIES ON THE VORTEX CORE STRUCTURE IN IRON-BASED SUPERCONDUCTORS

2012 ◽  
Vol 26 (21) ◽  
pp. 1230013
Author(s):  
POLINA BELOVA ◽  
IVAN ZAKHARCHUK ◽  
KONSTANTIN BORISOVICH TRAITO ◽  
ERKKI LÄHDERANTA
Keyword(s):  
Fermi Surface ◽  
Mixed State ◽  
Order Parameter ◽  
Spin Fluctuation ◽  
Pairing Symmetry ◽  
Gap Function ◽  
Spin Fluctuations ◽  
Field Range ◽  
Cutoff Parameter ◽  
Antiferromagnetic Spin

Effects of the order parameter symmetries on the cutoff parameter ξh (determining the magnetic field distribution) in the mixed state are investigated in the framework of quasiclassical Eilenberger theory for isotropic s±, s++ and anisotropic dx2-y2-wave superconducting pairings. These symmetries are proposed for the pairing state of the Fe -pnictides. In s± pairing symmetry, the gap function has opposite sign at the electron and hole pockets of the Fermi surface, it is connected with interband antiferromagnetic spin fluctuations. In s++ pairing symmetry, the gap function has the same sign at the Fermi surface, it is mediated by moderate electron–phonon interaction due to Fe -ion oscillation and the critical orbital fluctuation. The dx2-y2 pairing symmetry can rise from intraband antiferromagnetic spin fluctuation in strongly hole overdoped iron pnictide KFe 2 As 2 and ternary chalcogenides. The s± pairing symmetry results in different effects of intraband (Γ0) and interband (Γπ) impurity scattering on ξh. It is found that ξh/ξc2 value decreases with Γ0 leading to the values much less than those predicted by the analytical Ginzburg–Landau (AGL) theory for high Γ0. At very high Γ0, the interband scattering suppresses ξh/ξc2 considerably below one in the whole field range making it flat for both s± and s++ pairing symmetries. Scaling of the cutoff parameter with the electromagnetic coherence length shows the importance of the nonlocal effects in mixed state. The small values of ξh/ξc2 were observed in μSR measurements of Co -doped BaFe 2 As 2. If Γ0 and Γπ are small and equal than the ξh/ξc2(B/Bc2) dependence for s± symmetry behaves like that of the AGL model and shows a minimum with value much more than that obtained for s++ superconductors. With high Γπ, the ξh/ξc2(B/Bc2) dependence resides above the AGL curve for s± pairing symmetry, as observed in SANS measurements of stoichiometrical LiFeAs compound. In d-wave superconductors, ξh/ξc2 always increases with Γ similar to the s± symmetry case with Γ0 = Γπ.

scholarly journals Low-energy antiferromagnetic spin fluctuations limit the coherent superconducting gap in cuprates

2018 ◽  
Vol 98 (22) ◽  
Author(s):  
Yangmu Li ◽  
Ruidan Zhong ◽  
M. B. Stone ◽  
A. I. Kolesnikov ◽  
G. D. Gu ◽  
...  
Keyword(s):  
Low Energy ◽  
Spin Fluctuations ◽  
Superconducting Gap ◽  
Antiferromagnetic Spin

NMR evidence for antiferromagnetic spin fluctuations in superconducting λ-(BETS)2GaCl4

2003 ◽  
Vol 137 (1-3) ◽  
pp. 1297-1298 ◽  
Author(s):  
S. Takagi ◽  
D. Maruta ◽  
H. Sasaki ◽  
H. Uozaki ◽  
H. Tsuchiy ◽  
...  
Keyword(s):  
Spin Fluctuations ◽  
Antiferromagnetic Spin

Electronic Structure, Magnetism and Spin-Fluctuations in Fe-As Based Superconductors

2008 ◽  
Vol 1148 ◽  
Author(s):  
David Joseph Singh ◽  
Mao-Hua Du ◽  
Lijun Zhang ◽  
Alaska Subedi ◽  
Jiming An
Keyword(s):  
Electronic Structure ◽  
Fermi Surface ◽  
Density Functional ◽  
Density Wave ◽  
Spin Density Wave ◽  
Functional Results ◽  
Spin Fluctuations ◽  
Square Lattice ◽  
Itinerant Magnetism ◽  
Strong Spin

AbstractThe physical properties of the layered iron superconductors and related phases are discussed starting from first principles calculations. The electronic structure is described as that of metallic Fe2+ square lattice sheets with substantial direct Fe-Fe hopping and interactions with the neighboring anionic pnictogens or chalcogens. The materials have a semi-metallic band structure, and in particular the Fermi surface consists of small cylindrical electron sections centered at the zone corner, and compensating hole sections at the zone boundary. The density of states N(EF) is high placing the materials near itinerant magnetism in general, and furthermore the small Fermi surface sections are well nested leading to a tendency towards a spin density wave. Comparison of experimental and density functional results imply the presence of exceptionally strong spin fluctuations in these materials. Superconductivity is discussed within this context.

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