Superconductivity at 25 K in hole-doped (La _1-x Sr _x )OFeAs

Abstract

By partially substituting the tri-valence element La with di-valence element Sr in LaOFeAs, we introduced holes into the system. For the first time, we successfully synthesized the hole-doped new superconductors (La1−xSrx)OFeAs. The maximum superconducting transition temperature at about 25 K was observed at a doping level of x = 0.13. It is evidenced by Hall effect measurements that the conduction in this type of material is dominated by hole-like charge carriers, rather than electron-like ones. Together with the data of the electron-doped system La(O1−xFx)FeAs, a generic phase diagram is depicted and is revealed to be similar to that of the cuprate superconductors.

Synthesis and Properties of SmO0.5F0.5BiS2 and Enhancement in Tc in La1–ySmyO0.5F0.5BiS2

“…22,29 This is in contrast to what is observed in LnOFeAs where hole doping also induces superconductivity. [30][31][32] Electronic structure 3 of these chalcogenides is comparable to that of pnictides and is greatly influenced by doping. [33][34] Their bands near the Fermi level consist of states predominantly arising from Bi (6p) and S (3p)…”

Synthesis, Crystal Structure and Superconductivity in RbLn2Fe4As4O2(Ln = Sm, Tb, Dy, and Ho)

“…[1][2][3] The key structural unit for the emergence of superconductivity is the anti-fluorite-type Fe 2 X 2 (X = As, Se) layers, with which the parent (undoped) compounds mostly appear to be spin-density-wave (SDW) semi-metals. Superconductivity is induced by suppressing the SDW ordering via a certain chemical doping that may either introduce additional electrons 4 or holes, 5 or "apply" chemical pressures. 6 Nevertheless, there is an alternative route towards superconductivity as well, namely, the electron (or hole) carriers are introduced by an internal charge transfer in the material itself.…”

Superconductivity induced by doping Ru in SrFe2−xRuxAs2

“…Similar to the cuprates, the Fe-As layer is thought to be responsible for superconductivity and La-O layer is carrier reservoir layer to provide electron carrier. By replacing La with other rare earths, T c can be raised to above 50 K [2][3][4][5][6][7]. Late on, the oxygen-free iron arsenide compounds AFe 2 As 2 (denoted as FeAs-122) were discovered and superconductivity was found by appropriate substitution or under pressure [8][9][10][11][12][13].…”