AI 中文总结
本研究提出离域耦合簇（dCC）理论，用于准确模拟极化子基态与动力学，其成本低、精度高且可扩展，适用于模型系统及真实材料，结果与多种基准方法吻合。
AI 中文摘要
极化子基态及有限温度动力学的模拟仍具挑战性，因为现有方法难以同时具备非微扰精度、系统可改进性以及从模型到材料特定哈密顿量的可扩展性。我们引入一种针对极化子的平移不变变分耦合簇（CC）理论，称为离域CC（dCC），其能量为闭式形式，计算成本低至O(N³)且无需声子数截断。dCC能准确描述一维和二维Holstein模型、Su-Schrieffer-Heeger（光学及键）模型以及Fröhlich模型的基态，与密度矩阵重整化群（DMRG）和图解蒙特卡洛基准结果高度吻合。基于相同近似构建的投影切空间响应形式，可生成零温及有限温度下的电子添加谱函数和光电导率，所得谱与DMRG、Lanczos及神经网络量子态基准结果吻合良好，同时保留了物理解释性的激发层级，并能扩展至这些方法实际无法企及的二维有限温度晶格。该框架可直接应用于从头算电子-声子矩阵元，得到的LiF中电子极化子和空穴极化子结合能与最先进的多体计算结果匹配。这些结果确立了dCC作为一种统一变分框架，适用于从模型系统到真实材料的极化子基态及动力学研究。
英文摘要
Polaron ground states and finite-temperature dynamics remain challenging to simulate because existing methods struggle to combine nonperturbative accuracy, systematic improvability, and scalability from models to materials-specific Hamiltonians. We introduce a translationally invariant variational coupled-cluster (CC) theory for polarons, termed delocalized CC (dCC), with closed-form energies at cost as low as $\mathcal{O}(N^3)$ and no phonon-number cutoff. dCC accurately describes the ground states of the one- and two-dimensional Holstein and Su--Schrieffer--Heeger (optical and bond) models and the Fr{ö}hlich model, in close agreement with density matrix renormalization group (DMRG) and diagrammatic Monte Carlo benchmarks. A projected tangent-space response formalism built on the same ansatz yields electron-addition spectral functions and optical conductivities at zero and finite temperature. The resulting spectra agree well with DMRG, Lanczos, and neural-network quantum-state benchmarks while retaining a physically interpretable excitation hierarchy, and extend to two-dimensional lattices at finite temperature beyond the practical reach of these methods. The same framework applies directly to \textit{ab initio} electron--phonon matrix elements, yielding LiF electron- and hole-polaron binding energies that match state-of-the-art many-body calculations. These results establish dCC as a unified variational framework for polaron ground states and dynamics, from model systems to real materials.
