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Natural-orbital impurity solver and projection approach for Green's functions

机译:用于绿色功能的自然轨道杂质求解器和投影方法

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摘要

We extend a previously proposed rotation and truncation scheme to optimize quantum Anderson impurity calculations with exact diagonalization [Y. Lu, M. Hoppner, O. Gunnarsson, and M. W. Haverkort, Phys. Rev. B 90, 085102 (2014)] to density-matrix renormalization group (DMRG) calculations. The method reduces the solution of a full impurity problem with virtually unlimited bath sites to that of a small subsystem based on a natural impurity orbital basis set. The later is solved by DMRG in combination with a restricted-active-space truncation scheme. The method allows one to compute Green's functions directly on the real frequency or time axis. We critically test the convergence of the truncation scheme using a one-band Hubbard model solved in the dynamical mean-field theory. The projection is exact in the limit of both infinitely large and small Coulomb interactions. For all parameter ranges, the accuracy of the projected solution converges exponentially to the exact solution with increasing subsystem size.
机译:我们扩展了先前提出的旋转和截断方案,以优化具有精确的对角化的量子和杂质杂质计算[Y. Lu,M.Hoppner,O. Gunnarsson和M. W. Haverkort,Phy。 Rev. B 90,085102(2014)]密度 - 矩阵重新定位组(DMRG)计算。该方法基于天然杂质轨道基础集减少与小型子系统的几乎无限的浴地位的完全杂质问题的解决方案。稍后通过DMRG解决了与限制 - 有源空间截断方案的组合。该方法允许将绿色的功能直接计算在真实频率或时间轴上。我们批判地测试了在动态平均场理论中解决的单频哈布德模型的截断方案的收敛性。投影精确地是无限大和小库仑相互作用的限制。对于所有参数范围,投影解决方案的精度会聚到具有增加子系统尺寸的精确解决方案。

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  • 来源
    《Physical review》 |2019年第11期|115134.1-115134.9|共9页
  • 作者单位

    Heidelberg Univ Inst Theoret Phys Philosophenweg 19 D-69120 Heidelberg Germany;

    Max Planck Inst Solid State Res Heisenbergstr 1 D-70569 Stuttgart Germany;

    Max Planck Inst Solid State Res Heisenbergstr 1 D-70569 Stuttgart Germany|Max Planck Inst Chem Phys Solids Nothnitzer Str 40 D-01187 Dresden Germany;

    Heidelberg Univ Inst Theoret Phys Philosophenweg 19 D-69120 Heidelberg Germany;

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