Vafek Oskar, Chubukov Andrey V
Department of Physics and National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32306, USA.
School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota 55455, USA.
Phys Rev Lett. 2017 Feb 24;118(8):087003. doi: 10.1103/PhysRevLett.118.087003.
We present a novel mechanism of s-wave pairing in Fe-based superconductors. The mechanism involves holes near d_{xz}/d_{yz} pockets only and is applicable primarily to strongly hole doped materials. We argue that as long as the renormalized Hund's coupling J exceeds the renormalized interorbital Hubbard repulsion U^{'}, any finite spin-orbit coupling gives rise to s-wave superconductivity. This holds even at weak coupling and regardless of the strength of the intraorbital Hubbard repulsion U. The transition temperature grows as the hole density decreases. The pairing gaps are fourfold symmetric, but anisotropic, with the possibility of eight accidental nodes along the larger pocket. The resulting state is consistent with the experiments on KFe_{2}As_{2}.
我们提出了一种铁基超导体中s波配对的新机制。该机制仅涉及d_{xz}/d_{yz}口袋附近的空穴，主要适用于强空穴掺杂材料。我们认为，只要重整化的洪德耦合J超过重整化的轨道间哈伯德排斥力U^{'}，任何有限的自旋轨道耦合都会导致s波超导。即使在弱耦合情况下，且与轨道内哈伯德排斥力U的强度无关，这一结论依然成立。转变温度随着空穴密度的降低而升高。配对能隙具有四重对称性，但各向异性，沿着较大口袋可能存在八个偶然节点。所得状态与KFe_{2}As_{2}的实验结果一致。
