用于关联电子-声子系统的Ghost-RISB：在Hubbard-Holstein模型中的应用
Ghost-RISB for Correlated Electron-Phonon Systems: Application to the Hubbard-Holstein Model
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中文总结 AI 辅助
本文推广ghost-RISB方法并将其应用于Hubbard-Holstein模型，可高效准确描述关联电子-声子相互作用，计算成本远低于DMFT，揭示了双极化子区域超导序参量受抑制的Franck-Condon型效应。
中文摘要 AI 辅助
我们开发了ghost-旋转不变 slave-boson（ghost-RISB）方法的推广版本，该方法纳入了与任意格点电子自由度耦合的局域声子模式，可在高效变分框架内对电子-电子和电子-声子相互作用进行非微扰处理。该方法扩展了ghost轨道构造，以捕捉超出静态slave-boson方法的动力学自能效应和声子诱导重整化。针对Hubbard-Holstein模型，与动力学平均场理论（DMFT）结果的基准测试显示，在宽耦合强度范围内，电子准粒子权重和声子性质均呈现出色的定量一致性，且能准确捕捉电子-电子与电子-声子相互作用的竞争关系。我们表明，ghost轨道的纳入对准确描述低频、强动力学声子的区域至关重要。扩展后的ghost-RISB实现此精度的计算成本仅为DMFT的一小部分，因其自洽性根植于可观测量而非动力学可观测量，可快速探索关联电子-声子相图。我们利用此优势表征强耦合和声子绝热的最苛刻区域。我们的分析显示超导序参量受到抑制，这被解释为双极化子区域中与空位点和双占据位点相关的声子波函数重叠的Franck-Condon型减少。
英文摘要
We develop a generalization of the ghost-rotationally-invariant slave-boson (ghost-RISB) method that incorporates local phonon modes coupled to arbitrary on-site electronic degrees of freedom, enabling a nonperturbative treatment of electron-electron and electron-phonon interactions within an efficient variational framework. The method extends the ghost-orbital construction to capture dynamical self-energy effects and phonon-induced renormalizations beyond static slave-boson approaches. Benchmarking against dynamical mean-field theory (DMFT) results for the Hubbard-Holstein model, we find excellent quantitative agreement for electron quasiparticle weights and phonon properties across a wide range of coupling strengths, and it captures accurately the competition between electron-electron and electron-phonon interactions. We show that the inclusion of the ghost orbitals is crucial to accurately describe the regime of low-frequency, strongly dynamical, phonons. The extended ghost-RISB achieves this accuracy at a fraction of the computational cost of DMFT, due to its self-consistency rooted in static observables instead of dynamical ones, enabling rapid exploration of correlated electron-phonon phase diagrams. We exploit this advantage to characterize the most demanding regime of strong coupling and adiabatic phonons. Our analysis shows a suppression of the superconducting order parameter, which is interpreted as a Franck-Condon-like reduction of the overlap between the phonon wavefunctions associated with empty and doubly-occupied sites in the bipolaronic regime.
