论文标题
改进的自我能源数值重新归一化组计算的估计量
Improved estimator for numerical renormalization group calculations of the self-energy
论文作者
论文摘要
我们基于两个运动方程的组合提供了一个新的自我能源估计量，并讨论了其对数值重新归一化组（NRG）计算的益处。在具有挑战性的制度中，NRG是由标准估计器产生的，两个相关因子的比率通常遭受伪像：智障自我能源的虚构部分没有正确地归一化，并且在低能时，在低的能量下超出了无形的值并显示摇摆不定。我们表明，新的估计器可以在这些属性中解析伪像，因为它们可以直接从辅助相关器的假想部分确定，并且不涉及Kramers-Kronig Transform获得的实际部分。此外，我们发现新的估计器会以减少的数值努力（对于较低的保存状态）产生收敛的结果，因此在将NRG应用于多纤维系统时非常有价值。我们的分析针对的是量子杂质模型的NRG处理，尤其是在动态均值场理论中产生的量子模型，但是大多数结果可以直接概括为其他杂质或群集求解器。
We present a new estimator for the self-energy based on a combination of two equations of motion and discuss its benefits for numerical renormalization group (NRG) calculations. In challenging regimes, NRG results from the standard estimator, a ratio of two correlators, often suffer from artifacts: the imaginary part of the retarded self-energy is not properly normalized and, at low energies, overshoots to unphysical values and displays wiggles. We show that the new estimator resolves the artifacts in these properties as they can be determined directly from the imaginary parts of auxiliary correlators and do not involve real parts obtained by Kramers-Kronig transform. Furthermore, we find that the new estimator yields converged results with reduced numerical effort (for a lower number of kept states) and thus is highly valuable when applying NRG to multiorbital systems. Our analysis is targeted at NRG treatments of quantum impurity models, especially those arising within dynamical mean-field theory, but most results can be straightforwardly generalized to other impurity or cluster solvers.
