论文标题
从头开始，极性的自洽多体理论
Ab initio self-consistent many-body theory of polarons at all couplings
论文作者
论文摘要
我们提出了一个理论框架，以描述多体绿色功能形式主义中的第一原理。从一般的电子 - 音纸哈密顿量开始，我们得出了一个自洽的dyson方程，其中声子介导的自我能源由两个不同的术语组成。一个术语是扇形 - 式自我能源，并描述了动态电子 - 音波过程，另一个术语是对源自原子核的静态位移的自我能源的新贡献。对本理论的最低阶近似产生了在大极界极限的电子 - phonon相互作用的标准多体扰动理论方法，以及[Sio等人，Phys。 Rev. B 99，235139（2019）;物理。莱特牧师。 122，246403（2019）]在小极地的极限中。概述了在第一原理计算中实施当前统一形式主义的实用秘诀。我们将我们的方法应用于Fröhlich模型，并在所有耦合上获得明显准确的极性能量，这与Feynman的Polaron理论和图表蒙特卡洛计算相一致。我们还分别以弱和强耦合恢复了Fröhlich和Pekar的众所周知的结果。目前的方法可以在所有耦合下对实际材料中极性子的预测性多体计算。
We present a theoretical framework to describe polarons from first principles within a many-body Green's function formalism. Starting from a general electron-phonon Hamiltonian, we derive a self-consistent Dyson equation in which the phonon-mediated self-energy is composed by two distinct terms. One term is the Fan-Migdal self-energy and describes dynamic electron-phonon processes, the other term is a new contribution to the self-energy originating from the static displacements of the atomic nuclei in the polaronic ground state. The lowest-order approximation to the present theory yields the standard many-body perturbation theory approach to electron-phonon interactions in the limit of large polarons, and the ab initio polaron equations introduced in [Sio et al., Phys. Rev. B 99, 235139 (2019); Phys. Rev. Lett. 122, 246403 (2019)] in the limit of small polarons. A practical recipe to implement the present unifying formalism in first-principles calculations is outlined. We apply our method to the Fröhlich model, and obtain remarkably accurate polaron energies at all couplings, in line with Feynman's polaron theory and diagrammatic Monte Carlo calculations. We also recover the well-known results of Fröhlich and Pekar at weak and strong coupling, respectively. The present approach enables predictive many-body calculations of polarons in real materials at all couplings.
