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arXiv 1408.1407cond-mat.supr-concond-mat.str-el
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自旋三重态奇宇称超导电性接近II型范霍夫奇点的证据

Evidence for spin-triplet odd-parity superconductivity close to type-II van Hove singularities

Zi Yang Meng, Fan Yang, Kuang-Shing Chen, Hong Yao, Hae-Young Kee

摘要:

自BCS超导体发现以来,寻找非常规库珀配对态一直是超导研究的核心。特别是,自旋三重态奇宇称配对状态最近被重新审视,因为它有可能被调谐到拓扑超导体。在这种情况下,有趣的是注意到最近的建议,这种自旋三重态配对不稳定性发生时,带填充是范霍夫奇点(vHS)附近的动量远离时间反演不变动量命名为II型vHS。然而,这一结果是在弱耦合重整化群和费米面片近似下得到的。为了探索弱耦合费米面片近似下的超导不稳定性,我们采用三种不同的方法对二维正方晶格中的哈伯德模型进行了系统的研究:随机相位近似、大尺度动力学平均场论模拟和大尺度动力学团簇模拟.我们发现,在一个广泛的掺杂范围内,围绕II型范霍夫填充,一个两重简并,自旋三重态,奇宇称$p$波配对状态出现由于排斥相互作用,当费米面没有充分嵌套。我们的研究结果可能与最近发现的超导体LaO $_{1-x}$ F $_{x}$ BiS $_{2}$,Ir $_{1-x}$ Pt $_{x}$ Te $_{2}$和建议的掺杂BC $_{3}$的相关性也进行了讨论。

英文摘要:

Searching for unconventional Cooper pairing states has been at the heart of superconductivity research since the discovery of BCS superconductors. In particular, spin-triplet odd-parity pairing states were recently revisited due to the possibility of tuning towards topological superconductors. In this context, it is interesting to note a recent proposal that such a spin-triplet pairing instability occurs when the band filling is near van Hove singularities (vHS) associated with momenta away from time-reversal invariant momenta named type-II vHS. However, this result was obtained within a weak coupling renormalization group with Fermi surface patch approximation. To explore superconducting instabilities beyond this weak coupling Fermi surface patch approximation, we perform systematic study on Hubbard model in a two-dimensional square lattice using three different methods: random phase approximation, large-scale dynamical mean field theory simulations with continuous time quantum Monte Carlo (CTQMC) impurity solver, and large-scale dynamical cluster simulations with CTQMC cluster solver. We find, in a wide doping range centered around the type-II van Hove filling, a two-fold degenerate, spin-triplet, odd-parity $p$-wave pairing state emerges due to repulsive interaction, when the Fermi surface is not sufficiently nested. Possible relevance of our findings to the recently discovered superconductors LaO$_{1-x}$F$_{x}$BiS$_{2}$, Ir$_{1-x}$Pt$_{x}$Te$_{2}$ and proposed doped BC$_{3}$ are also discussed.

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