论文标题
低温旋转波动和超导率的有效波动交换方法：从哈伯德模型到na $ _x $ coo $ _2 \ cdot y $ h $ h $ _2 $ o
Efficient fluctuation exchange approach to low-temperature spin fluctuations and superconductivity: from the Hubbard model to Na$_x$CoO$_2\cdot y$H$_2$O
论文作者
论文摘要
超导性主要在能量和温度尺度上比典型的裸露电子能小得多。由于示意性多体技术的计算工作随着所需的Matsubara频率的数量而增加，因此在低温下发生的相变很难解决。在这项工作中，我们使用“中间表示基础”（IR）[Shinaoka等，PRB 96，2017]来实施一种波动交换（FLEX）方法来进行自旋波动和超导性，以获得Matsubara绿色功能。这种flex+ir方法在数值上非常有效，使我们能够以$ 10^{ - 4} $在多轨系统中的电子带宽度的单位达到温度。在平方晶格上的掺杂排斥性哈伯德模型中基准测试方法后，我们研究了在水合钠钴材料Na $ _x $ _x $ _x $ _2 $ _2 \ coo $ _2 \ cdot y $ $ h $ _2 $ o到实验过渡温度的规模的可能性中 以下。
Superconductivity arises mostly at energy and temperature scales that are much smaller than the typical bare electronic energies. Since the computational effort of diagrammatic many-body techniques increases with the number of required Matsubara frequencies and thus with the inverse temperature, phase transitions that occur at low temperatures are typically hard to address numerically. In this work, we implement a fluctuation exchange (FLEX) approach to spin fluctuations and superconductivity using the "intermediate representation basis" (IR) [Shinaoka et al., PRB 96, 2017] for Matsubara Green functions. This FLEX+IR approach is numerically very efficient and enables us to reach temperatures on the order of $10^{-4}$ in units of the electronic band width in multi-orbital systems. After benchmarking the method in the doped repulsive Hubbard model on the square lattice, we study the possibility of spin-fluctuation-mediated superconductivity in the hydrated sodium cobalt material Na$_x$CoO$_2\cdot y$H$_2$O reaching the scale of the experimental transition temperature $T_{\mathrm{c}}=4.5$ K and below.
