Two-dome structure in electron-doped iron arsenide superconductors
Two-dome structure in electron-doped iron arsenide superconductors
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DOI：
10.1038/ncomms1913
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发表时间：
2012-07-01
影响因子：
16.6
通讯作者：
Hosono, Hideo
中科院分区：
文献类型：
--
作者：
Iimura, Soshi;Matuishi, Satoru;Hosono, Hideo
基于材料 LaFeAsO1-xFx 的砷化铁超导体的特点是二维费米面 (FS)，由空穴和电子袋组成，在 x = 0 时产生结构和反铁磁转变。通过用 F- 取代 O2- 进行电子掺杂，抑制这些转变，并在 x = 0.1 时产生最大 T-c 为 26 K 的超导性。然而，由于 F- 在 x = 0.2 以上溶解度较差，因此无法进入过掺杂区域。在这里，我们通过在 LaFeAsO 中掺杂氢来克服这个问题。我们报告了 LaFeAsO1-xHx (x < 0.53) 的相图，除了 LaFeAsO1-xFx 中看到的传统超导圆顶之外，我们还发现了 0.21 < x < 0.53 范围内的第二个圆顶，在 x = 0.3 时最大 T-c 为 36 K。密度泛函理论计算表明，三个 Fe 3d 能带（xy、yz 和 zx）在 x = 0.36 时变得简并，而 FS 嵌套随着 x 单调减弱。这些结果表明能带简并对于诱导高 T-c 具有重要作用。
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 T-c of 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 T-c of 36 K at x = 0.3. Density functional theory calculations reveal that the three Fe 3d bands (xy, yz and 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 T-c.