Doping Dependence of the Pressure Response of T_c in the SmO_(1-x)F_xFeAs Superconductors

摘要

The discovery of superconductivity in the family of fluorine-doped rare-earth iron oxyarsenides, REO_(1-x)F_xFeA_s (RE = La, Ce, Pr, Nd, Sm, Gd) with transition temperatures, T_c as high as 55 K is currently generating considerable interest. These systems adopt tetragonal crystal structures (ZrCuSiAs-type, space group PAInmm), comprising interleaved two-dimensional RE(O,F) and FeAs layers (Figure 1 inset) with the latter providing the carrier conduction pathway. The appearance of high T_c superconductivity in these materials is generating exciting arguments on the possible mechanism of superconductivity and has led to considerable optimism for raising T_c to even higher values. In particular, it appears that superconductivity emerges at some critical value of F-doping when a competing spin-density-wave (SDW)-type long-range antiferro-magnetic (AFM) order collapses; T_c increases smoothly with increasing doping level x until it reaches a maximum and then it decreases.