Iron arsenide superconductors based on the material LaFeAsO1-xFx are characterized by a two-dimensional Fermi surface (FS) consisting of hole and electron pockets yielding structural and antiferromagnetic transitions at x = 0. Electron doping by substituting O2- with F- suppresses these transitions and gives rise to superconductivity with a maximum Tc = 26 K at x = 0.1. However, the over-doped region cannot be accessed due to the poor solubility of F- above x = 0.2. Here we overcome this problem by doping LaFeAsO with hydrogen. We report the phase diagram of LaFeAsO1-xHx (x < 0.53) and, in addition to the conventional superconducting dome seen in LaFeAsO1-xFx, we find a second dome in the range 0.21 < x < 0.53, with a maximum Tc of 36 K at x = 0.3. Density functional theory calculations reveal that the three Fe 3d bands (xy, yz, zx) become degenerate at x = 0.36, whereas the FS nesting is weakened monotonically with x. These results imply that the band degeneracy has an important role to induce high Tc.
@article{arxiv.1207.0583,
title = {Two-dome structure in electron-doped iron arsenide superconductors},
author = {Soshi Iimura and Satoru Matuishi and Hikaru Sato and Taku Hanna and Yoshinori Muraba and Sung Wng Kim and Jung Eun Kim and Masaki Takata and Hideo Hosono},
journal= {arXiv preprint arXiv:1207.0583},
year = {2015}
}
Comments
31 pages, 4 figures, 1 table and supplementary information