Superconductivity at 43 K in SmFeAsO1-xF x

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

“…For the pressures up to 5.8 GPa, the spectra are well described by a single quadrupole doublet with hyperfine parameters similar to those found for the same sample at ambient pressure [11]. The quadrupole splitting, ΔE Q = 0.28 (2) mms -1 , and isomer shift, δ = 0.44(1) mms -1 at 0.2 GPa can be attributed to formally divalent Fe ions in a distorted tetrahedral surrounding of Se neighbors with strong covalency in the Fe-Se bonds. At 7.2 GPa a new phase appears in the spectrum with a relative intensity of ca.…”

“…Superconductivity has recently been discovered in iron arsenides [1][2][3][4][5][6], with superconducting transition temperatures (T c 's) as high as 55 K [6]. The superconductivity in this class of materials is unexpected because most Fe-based compounds display strong magnetic behavior.…”

Unusual superconducting state at 49 K in electron-doped CaFe 2 As 2 at ambient pressure

“…They consist of the similar FeSe-layers to carry the majority of the conducting carriers. However, the maximum T c s obtained for different classes of both families are 57 K for 1111 (10,11); 38 K for 122 (3,4,12); 18-31 K for 111 (5, 6); and 8-37 K for 11 (8,9), through doping and/or pressurization. In spite of the similar layered structures, T c s of Fe-pnictides and -chalcogenides are much lower than those of the cuprates, which possess the CuO 2 -layers (13).…”

Doping-insensitive density-of-states suppression in polycrystalline iron-based superconductor

“…with transition temperatures (T c 's) well beyond the McMillan limit for BCS superconductors has rejuvenated intensive research on unconventional superconductivity [1,2,3,4,5,6,7]. In some ways, the layered structure of a iron-based superconductor resembles the high-T c cuprates: LnO 1−x F x layers act as the charge reservoir, and FeAs layers act as the conducting layers.…”