Density-matrix renormalization group study of optical conductivity of the Mott insulator for two-dimensional clusters
Density-matrix renormalization group study of optical conductivity of the Mott insulator for two-dimensional clusters
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DOI：
10.1103/physrevb.104.205123
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发表时间：
2021-09
影响因子：
3.7
通讯作者：
K. Shinjo;Yoshiki Tamaki;S. Sota;T. Tohyama
中科院分区：
文献类型：
--
作者：
K. Shinjo;Yoshiki Tamaki;S. Sota;T. Tohyama
莫特绝缘体的光电导率的实部$\text{Re}\sigma(\omega)$包含了自旋和电荷自由度如何相互作用的大量信息。利用随时间变化的密度矩阵重整化群，研究了半填充方形晶格上二维Hubbard模型$\text{Re}\sigma(\omega)$的性质。我们在$\text{Re}\sigma(\omega)$的莫特间隙边缘发现了一个激子峰，这不仅适用于二维方形晶格，也适用于两腿和四腿阶梯。然而，对于方形晶格，我们没有清楚地发现激子峰和连续带之间的间隙，这表明束缚态没有很好地定义。$\text{Re}\sigma(\omega)$中激子峰的出现暗示了自旋极化子的形成。通过考察$\text{Re}\sigma(\omega)$对现场库仑相互作用和次近邻跳变的依赖性，我们证实了一个激子峰是由磁效应产生的。由于激子峰的谱宽很窄，电子-声子相互作用引起的电子散射很容易抑制激子峰。通过模拟La $_{2}$ CuO $_{4}$和Nd $_{2}$ CuO $_{4}$中存在的电子-声子耦合，在$\text{Re}\sigma(\omega)$中引入一个大的展宽，我们得到了与实验相当的$\text{Re}\sigma(\omega)$。
The real part of optical conductivity $\text{Re}\sigma(\omega)$ of the Mott insulators has a large amount of information on how spin and charge degrees of freedom interact with each other. By using the time-dependent density-matrix renormalization group, we study $\text{Re}\sigma(\omega)$ of the two-dimensional Hubbard model on a square lattice at half filling. We find an excitonic peak at the Mott-gap edge of $\text{Re}\sigma(\omega)$ not only for the two-dimensional square lattice but also for two- and four-leg ladders. For the square lattice, however, we do not clearly find a gap between an excitonic peak and continuum band, which indicates that a bound state is not well defined. The emergence of an excitonic peak in $\text{Re}\sigma(\omega)$ implies the formation of a spin polaron. Examining the dependence of $\text{Re}\sigma(\omega)$ on the on-site Coulomb interaction and next-nearest neighbor hoppings, we confirm that an excitonic peak is generated from a magnetic effect. Electron scattering due to an electron-phonon interaction is expected to easily suppress an excitonic peak since spectral width of an excitonic peak is very narrow. Introducing a large broadening in $\text{Re}\sigma(\omega)$ by modeling the electron-phonon coupling present in La$_{2}$CuO$_{4}$ and Nd$_{2}$CuO$_{4}$, we obtain $\text{Re}\sigma(\omega)$ comparable with experiments.