In this work, the study of the spectral properties of an open interacting system by solving the generalized Kadanoff‐Baym ansatz (GKBA) master equation for the single‐particle density matrix, namely the time‐diagonal lesser Green's function, is reported. To benchmark its validity, the solution obtained within the GKBA is compared with the solution of the Dyson equation at stationarity. In both approaches, the interaction is treated within the self‐consistent second‐order Born approximation, whereas the GKBA still retains the retarded propagator calculated at the Hartree–Fock (HF) and wideband limit approximation level. The model chosen is that of two leads connected through a central correlated region where particles can interact and utilize the stationary particle current at the boundary of the junction as a probe of the spectral features of the system. The central region is chosen as the simplest model featuring a degenerate ground state with a flat band. The main result is that the solution of the GKBA master equation captures well the spectral feature of such system and specifically the transition from dispersionless to dispersive behavior of the flat band as the interaction is increased. Therefore, the GBKA solution retains the main spectral features of the self‐energy used even when the propagator is at the HF level.

中文翻译：

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广义 Kadanoff-Baym Ansatz 平带系统中电子的相互作用

在这项工作中，报告了通过求解单粒子密度矩阵的广义 Kadanoff-Baym ansatz (GKBA) 主方程（即时间对角小格林函数）来研究开放相互作用系统的光谱特性。为了衡量其有效性，将 GKBA 内获得的解与平稳状态下戴森方程的解进行比较。在这两种方法中，相互作用都是在自洽二阶玻恩近似内处理的，而 GKBA 仍然保留在 Hartree-Fock (HF) 和宽带极限近似水平上计算的延迟传播器。所选择的模型是通过中心相关区域连接的两条引线的模型，在该区域中粒子可以相互作用并利用连接点边界处的静止粒子电流作为系统光谱特征的探针。中心区域被选为最简单的模型，具有具有平带的简并基态。主要结果是 GKBA 主方程的解很好地捕捉了此类系统的光谱特征，特别是随着相互作用的增加，平带从无色散行为到色散行为的转变。因此，即使传播器处于高频水平，GBKA 解决方案也保留了所使用的自能的主要光谱特征。