论文标题
通过宽和窄带之间的一对波动增强了超导性
Superconductivity enhanced by pair fluctuations between wide and narrow bands
论文作者
论文摘要
已知Fermi水平附近的全狭窄带或空的窄带通过促进散射过程和自旋波动来增强超导性。在这里，我们证明了具有半狭窄频带的系统中的Doublon-Holon波动可以同样提高超导$ T_C $。我们使用动态平均场理论研究了方格上的半填充双层式哈伯德模型。非相互作用系统的带状结构包含由粘结轨道形成的宽带和由抗跨轨道形成的狭窄带，带宽可以通过层间跳动来调节。窄带的收缩会导致宽带中超导顺序参数和相位刚度的大幅增加。同时，与宽带的耦合使狭窄的频带可以在平坦带限制下保持超导 - 并达到最大的阶参数。我们开发了一种异常的蠕虫抽样方法来研究有效跳跃的极限的超导性。通过分析局部本征态的直方图，我们阐明了在键合/抗抗方向基础中不同相互作用项之间的相互作用如何促进对的波动和超导性。
Full or empty narrow bands near the Fermi level are known to enhance superconductivity by promoting scattering processes and spin fluctuations. Here, we demonstrate that doublon-holon fluctuations in systems with half-filled narrow bands can similarly boost the superconducting $T_c$. We study the half-filled attractive bilayer Hubbard model on the square lattice using dynamical mean-field theory. The band structure of the noninteracting system contains a wide band formed by bonding orbitals and a narrow band formed by antibonding orbitals, with bandwidths tunable by the inter-layer hopping. The shrinking of the narrow band can lead to a substantial increase in the superconducting order parameter and phase stiffness in the wide band. At the same time, the coupling to the wide band allows the narrow band to remain superconducting -- and to reach the largest order parameter -- in the flat band limit. We develop an anomalous worm sampling method to study superconductivity in the limit of vanishing effective hopping. By analyzing the histogram of the local eigenstates, we clarify how the interplay between different interaction terms in the bonding/antibonding basis promotes pair fluctuations and superconductivity.
