Superconductivity at 27K in tetragonal FeSe under high pressure

Abstract

A huge enhancement of the superconducting transition temperature T c was observed in a tetragonal FeSe superconductor under high pressure. The onset temperature was as high as 27 K at 1.48 GPa and the pressure coefficient showed an extremely high value of 9.1 K/GPa. The upper critical field H c2 was estimated to be ~ 72 T at 1.48 GPa. Because of the high H c2 , the FeSe system can be applied to superconducting wire rods.Since the great discovery of cuprate high-T c superconductors, over 20 years have passed. Recently many researchers have made much effort focused on non-cuprate, new superconductors such as MgB 2 with a T c of 39 K. 1,2,3

Large local disorder in superconducting K0.8Fe1.6Se2studied by extended x-ray absorption fine structure

“…Susbstitution by Te in the FeSe leads to a marginal increase in the T c (∼ 15 K), however, the system gets phase separated and the nanoscale structure is characterized by different iron-chalcogen bondlengths [8]. On the other hand, the superconducting transition temperature of the FeSe shows large enhancement up to ∼37 K under the hydrostatic pressure [6,7]. A large pressure sensitivity of the FeSe indicates chemical pressure being a potential alternative parameter for raising its T c .…”

Electronic and magnetic phase diagram of β-Fe1.01Se with superconductivity at 36.7 K under pressure

“…These properties suggest that the superconductivity in the iron arsenides is unconventional, with electron pairing possibly mediated by magnetic interactions. More recently, superconductivity has been reported at 8.5 K [9], increasing up to 27 K under pressure [10], in the structurally related material iron selenide [11,12]. Iron selenide and the iron arsenides share a common structural motif, containing Fe 2 X 2 (X=As, Se) layers of edge-shared FeX 4 tetrahedra, suggesting that the mechanism of superconductivity may be the same in both families in spite of the low T c for the selenide.…”

Increase in T c and Change of Crystal Structure by High-Pressure Annealing in BiS2-Based Superconductor CeO0.3 F 0.7BiS2

“…2,9) Electrical resistivity and magnetic susceptibility measurements under high pressure revealed that the transition temperature (T c ) of the BiS 2 -based family was sensitive to application of external pressure and can be significantly increased [11][12][13] as observed in the Fe-based superconductor family. [14][15][16][17] In addition, superconducting properties of the BiS 2 -based superconductors strongly depend on the sample preparation method. Solid-state-reacted (As-grown) LaO 1-x F x BiS 2 shows filamentary superconductivity: in other words, the superconducting volume fraction is obviously low, whereas superconducting states are evidently generated.…”