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首页> 外文期刊>Physical review >Superconductivity from repulsion in LiFeAs:Novel s-wave symmetry and potential time-reversal symmetry breaking
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Superconductivity from repulsion in LiFeAs:Novel s-wave symmetry and potential time-reversal symmetry breaking

机译：LiFeAs中斥力的超导性：新颖的s波对称性和可能的​​时间反转对称性破坏

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摘要

We analyze the structure of the pairing interaction and superconducting gap in LiFeAs by decomposing the pairing interaction for various k_z cuts into s- and d-wave components and by studying the leading superconducting instabilities. We use the ten-orbital tight-binding model, derived from ab initio LDA calculations with hopping parameters extracted from the fit to ARPES experiments. We find that the pairing interaction almost decouples between two subsets; one consists of the outer hole pocket and two electron pockets, which are quasi-2D and are made largely out of the d_(xy) orbital, and the other consists of the two inner hole pockets, which are quasi-3D and are made mostly out of d_(xz) and d_(yz) orbitals. Furthermore, the bare interpocket and intrapocket interactions within each subset are nearly equal. In this situation, small changes in the intrapocket and interpocket interactions due to renormalizations by high-energy fermions give rise to a variety of different gap structures. We focus on s-wave pairing which, as experiments show, is the most likely pairing symmetry in LiFeAs. We find four different configurations of the s-wave gap immediately below T_c: one in which the superconducting gap changes sign between two inner hole pockets and between the outer hole pocket and two electron pockets, one in which the gap changes sign between two electron pockets and three hole pockets, one in which the gap on the outer hole pocket differs in sign from the gaps on the other four pockets, and one in which the gaps on two inner hole pockets have one sign and the gaps on the outer hole pockets and on electron pockets have different sign. Different s-wave gap configurations emerge depending on whether the renormalized interactions increase attraction within each subset or increase the coupling between particular components of the two subsets. We discuss the phase diagram and experimental probes to determine the structure of the superconducting gap in LiFeAs. We argue that the state with opposite sign of the gaps on the two inner hole pockets has the best overlap with ARPES data. We also argue that at low T, the system may enter into a "mixed" s + is state, in which the phases of the gaps on different pockets differ by less than π and time-reversal symmetry is spontaneously broken.
机译：通过将各种k_z切口的配对相互作用分解为s和d波分量，并研究主要的超导不稳定性，我们分析了LiFeAs中配对相互作用和超导间隙的结构。我们使用十轨道紧密结合模型，该模型是从头算LDA计算得出的，而跳变参数是从ARPES实验拟合中提取的。我们发现配对互动几乎在两个子集之间解耦。一个由外空穴腔和两个电子腔组成，它们大致是d_xy轨道上的准2D腔，而另一个则由两个内部空穴腔，它们由准3D轨道组成，主要是d_（xy）轨道。在d_（xz）和d_（yz）轨道之外。此外，每个子集内的裸露的口袋间和口袋内的相互作用几乎相等。在这种情况下，由于高能费米子的重新归一化，口袋内和口袋间相互作用的细微变化会引起多种不同的间隙结构。如实验所示，我们将重点放在s波配对上，这是LiFeAs中最可能的配对对称性。我们在T_c的正下方找到了s波间隙的四种不同配置：一种超导间隙在两个内空穴腔之间以及外空穴腔和两个电子腔之间改变符号，一种在间隙中改变两个电子腔之间的符号。和三个孔穴，其中一个在外孔穴上的缝隙与在其他四个穴位上的缝隙的符号不同，另一个在其中两个内孔穴上的缝隙具有一个符号，在外孔穴上的缝隙和电子口袋上的符号不同。根据重新规范化的相互作用是增加每个子集内的吸引力还是增加两个子集的特定分量之间的耦合，会出现不同的s波间隙配置。我们讨论了相图和实验探针以确定LiFeAs中超导间隙的结构。我们认为，两个内孔腔的间隙符号相反的状态与ARPES数据具有最佳重叠。我们还认为，在低T时，系统可能进入“混合” s +状态，其中不同型腔上的间隙相位相差小于π，并且自发破坏了时间反转对称性。

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  • 来源
    《Physical review》 |2014年第14期|144513.1-144513.19|共19页
  • 作者

    F. Ahn; I. Eremin; J. Knolle; V. B. Zabolotnyy; S. V. Borisenko; B. Buechner; A. V. Chubukov;

  • 作者单位

    Institut fuer Theoretische Physik III, Ruhr-Universitaet Bochum, D-44801 Bochum, Germany;

    Institut fuer Theoretische Physik III, Ruhr-Universitaet Bochum, D-44801 Bochum, Germany;

    Max Planck Institute for the Physics of Complex Systems, D-01187 Dresden, Germany;

    Leibniz-Institut fuer Festkoerper- und Werkstofforschung Dresden, P.O. Box270116, D-01171 Dresden, Germany;

    Leibniz-Institut fuer Festkoerper- und Werkstofforschung Dresden, P.O. Box270116, D-01171 Dresden, Germany;

    Leibniz-Institut fuer Festkoerper- und Werkstofforschung Dresden, P.O. Box270116, D-01171 Dresden, Germany;

    Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA;

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  • 正文语种 eng
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  • 关键词

    band and itinerant models; pairing symmetries (other than s-wave); transition temperature variations;

    机译：带和巡回模型配对对称性（s波除外）;转变温度变化;

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