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首页> 外文期刊>Physical review >Multisite Versus Multiorbital Coulomb Correlations Studied Within Finite-temperature Exact Diagonalization Dynamical Mean-field Theory
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Multisite Versus Multiorbital Coulomb Correlations Studied Within Finite-temperature Exact Diagonalization Dynamical Mean-field Theory

机译：有限温度精确对角化动力学平均场理论研究的多站点与多轨道库仑相关性

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The influence of short-range Coulomb correlations on the Mott transition in the single-band Hubbard model at half filling is studied within cellular dynamical mean-field theory for square and triangular lattices. Finite-temperature exact diagonalization is used to investigate correlations within two-, three-, and four-site clusters. Transforming the nonlocal self-energy from a site basis to a molecular-orbital basis, we focus on the interor-bital charge transfer between these cluster molecular orbitals in the vicinity of the Mott transition. In all cases studied, the charge transfer is found to be small, indicating weak Coulomb-induced orbital polarization despite sizable level splitting between orbitals. These results demonstrate that all cluster molecular orbitals take part in the Mott transition and that the insulating gap opens simultaneously across the entire Fermi surface. Thus, at half filling we do not find orbital-selective Mott transitions or a combination of band filling and Mott transition in different orbitals. Nevertheless, the approach toward the transition differs greatly between cluster orbitals, giving rise to a pronounced momentum variation along the Fermi surface, in agreement with previous works. The near absence of Coulomb-induced orbital polarization in these clusters differs qualitatively from single-site multiorbital studies of several transition-metal oxides, where the Mott phase exhibits nearly complete orbital polarization as a result of a correlation driven enhancement of the crystal-field splitting. The strong single-particle coupling among cluster orbitals in the single-band case is identified as the source of this difference.
机译：在蜂窝动态均场理论的正方形和三角形晶格中研究了短程库仑相关对单带Hubbard模型半填充时Mott跃迁的影响。有限温度精确对角线化用于研究两个，三个和四个位点群集中的相关性。将非局部自能从位点转换为分子轨道，我们将重点放在在Mott跃迁附近的这些簇分子轨道之间的轨道间电荷转移。在所研究的所有情况下，都发现电荷转移很小，表明尽管在轨道之间有相当大的能级分裂，但库仑诱导的轨道极化很弱。这些结果表明，所有簇分子轨道都参与了莫特跃迁，并且绝缘间隙同时在整个费米表面上打开。因此，在半填充时，我们找不到在不同轨道上的轨道选择性莫特跃迁或带填充和莫特跃迁的组合。然而，与先前的工作一致，在簇轨道之间过渡的方法大不相同，导致沿费米表面的动量变化明显。在这些簇中几乎不存在库仑诱导的轨道极化，这与几种过渡金属氧化物的单点多轨道研究在质量上有所不同，在该研究中，由于相关驱动晶体场分裂的增强，Mott相显示出几乎完全的轨道极化。 。在单波段情况下，簇轨道之间的强单粒子耦合被认为是造成这种差异的原因。

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