论文标题
$（n+1）$ - 多型哈伯德模型中的$（n+1）$（n+1）
Stability of $(N+1)$-body fermion clusters in multiband Hubbard model
论文作者
论文摘要
我们从一种各种方法开始，并为$ n $相同旋转的边界状态得出一组耦合的积分方程 - $ \ uparrow $ fermions和一个单旋转 - $ \ downarrow $ fermion在通用的多型hubbard hamiltonian中具有有吸引力的现场交互。作为例证，我们将积分方程式应用于一维锯齿晶格，最高为$ n \ le 3 $，即，即$（3+1）$ - 身体问题，不仅揭示了在这个两频段模型中的四聚体状态，而且还揭示了其准时分散量时的Quasi-flat分散。此外，对于$ n = \ {4，5，\ cdots，10 \} $，我们的DMRG仿真和精确的对角度表明存在具有较低和较低绑定能的较大和较大的多组，可以想象，没有$ n $的上限。这些独特的$（n+1）$ - 车身簇与单波段线性链模型的确切结果形成鲜明对比，即$ n \ ge 2 $多聚机都不会出现。因此，必须考虑到平面系统中多体现象的正确描述，例如，它们可能会抑制超导性，尤其是在存在较大的旋转失衡时。
We start with a variational approach and derive a set of coupled integral equations for the bound states of $N$ identical spin-$\uparrow$ fermions and a single spin-$\downarrow$ fermion in a generic multiband Hubbard Hamiltonian with an attractive onsite interaction. As an illustration we apply our integral equations to the one-dimensional sawtooth lattice up to $N \le 3$, i.e., to the $(3+1)$-body problem, and reveal not only the presence of tetramer states in this two-band model but also their quasi-flat dispersion when formed in a flat band. Furthermore, for $N = \{4, 5, \cdots, 10 \}$, our DMRG simulations and exact diagonalization suggest the presence of larger and larger multimers with lower and lower binding energies, conceivably without an upper bound on $N$. These peculiar $(N+1)$-body clusters are in sharp contrast with the exact results on the single-band linear-chain model where none of the $N \ge 2$ multimers appear. Hence their presence must be taken into account for a proper description of the many-body phenomena in flat-band systems, e.g., they may suppress superconductivity especially when there exists a large spin imbalance.
