论文标题
通过电子掺杂铁硒的隐藏自旋波动的超导性
Superconductivity by Hidden Spin Fluctuations in Electron-Doped Iron Selenide
论文作者
论文摘要
Berg，Metlitski和Sachdev，Science 338，1606（2012）表明，通过具有两个轨道的传导电子对隐藏的自旋波动的交换可能会导致铜氧化物材料中的高温超导性。我们引入了类似的模型，用于掺杂电子的高温铁羟尼底超导体。传导电子携带最小的3D XZ和3D YZ铁原子轨道。棋盘板波动q_af处的低能隐藏自旋波动是由中心嵌套的费米表面和未折叠（一号铁）布里鲁因区域的嵌套的费米表面产生的。通过硒原子进行的超级交换相互作用引起的磁挫败感稳定了Q_AF与真实自旋波动处的隐藏自旋波动。在一半填充时，纯粹基于隐藏自旋波动的交换的Eliashberg理论揭示了LIFSHITZ向折叠（两种铁）布里群区域的转角的Electron/hole fermi表面袋过渡，但具有消失的光谱。因此，潜在的隐藏旋转密度地面底物是mott绝缘子。电子掺杂后，Eliashberg理论发现，孔费米表面袋的光谱重量仍然很小，而较大的电子费米表面口袋的光谱重量变得可观。因此，该预测与通过角度分辨光发射光谱（ARPES）在电子掺杂的硒氧化铁中仅观察到电子表面袋的观察。埃里亚斯贝格（Eliashberg）理论还发现，在电子掺杂时具有S+ - 超导性的不稳定性，以及各向同性库珀对，可在可见的电子费米表面口袋和微弱的孔费米表面口袋之间交替。与通过ARPE和扫描隧道显微镜（STM）在电子掺杂的铁硒化铁中观察到的各向同性能隙的比较与短距离隐藏的磁序一致。
Berg, Metlitski and Sachdev, Science 338, 1606 (2012), have shown that the exchange of hidden spin fluctuations by conduction electrons with two orbitals can result in high-temperature superconductivity in copper-oxide materials. We introduce a similar model for high-temperature iron-selenide superconductors that are electron doped. Conduction electrons carry the minimal 3d xz and 3d yz iron-atom orbitals. Low-energy hidden spin fluctuations at the checkerboard wavevector Q_AF result from nested Fermi surfaces at the center and at the corner of the unfolded (one-iron) Brillouin zone. Magnetic frustration from super-exchange interactions via the selenium atoms stabilize hidden spin fluctuations at Q_AF versus true spin fluctuations. At half filling, Eliashberg theory based purely on the exchange of hidden spin fluctuations reveals a Lifshitz transition to electron/hole Fermi surface pockets at the corner of the folded (two-iron) Brillouin zone, but with vanishing spectral weights. The underlying hidden spin-density wave groundstate is therefore a Mott insulator. Upon electron doping, Eliashberg theory finds that the spectral weights of the hole Fermi surface pockets remain vanishingly small, while the spectral weights of the larger electron Fermi surface pockets become appreciable. This prediction is therefore consistent with the observation of electron Fermi surface pockets alone in electron-doped iron selenide by angle-resolved photoemission spectroscopy (ARPES). Eliashberg theory also finds an instability to S+- superconductivity at electron doping, with isotropic Cooper pairs that alternate in sign between the visible electron Fermi surface pockets and the faint hole Fermi surface pockets. Comparison with the isotropic energy gaps observed in electron-doped iron selenide by ARPES and by scanning tunneling microscopy (STM) is consistent with short-range hidden magnetic order.
