论文标题
声子自能校正：屏幕或不屏幕
Phonon Self-Energy Corrections: To Screen, or Not to Screen
论文作者
论文摘要
声子的第一原理计算通常基于绝热近似和布里鲁因区采样，这些采样可能并不总是足以捕获Kohn异常的微妙之处。这些缺点可以通过对低能电子产生的声子自我能源的校正来解决。确切的自我能量涉及裸露和筛选的电子波顶的产物[Rev。 mod。物理。 89，015003（2017）];尽管如此，计算通常采用两个绝热筛选的顶点，这些顶点被认为是自我能量差异的可靠近似值[Phys。 Rev. B 82，165111（2010）]。我们评估了两种方法在估计模型汉密尔顿人的声子频谱函数和单层tas $ _2 $和掺杂的MOS $ _2 $的绝热低温声子分散体时的准确性。我们发现，由于其设计的误差取消了一阶，因此近似方法以低计算成本的形式产生了出色的校正，而使用裸露的顶点原则上可以改善这些结果，但在实践中却很具有挑战性。我们提供基于对部分筛选的声子和互动[Phys的下降折叠的替代策略。 Rev. B 92，245108（2015）]。这是一种自然的方案，包括电子 - 电子相互作用和在强相关的材料中的铲球和铲球声子以及电子 - 光子顶点的频率依赖性。
First-principles calculations of phonons are often based on the adiabatic approximation and on Brillouin-zone samplings that might not always be sufficient to capture the subtleties of Kohn anomalies. These shortcomings can be addressed through corrections to the phonon self-energy arising from the low-energy electrons. The exact self-energy involves a product of a bare and a screened electron-phonon vertex [Rev. Mod. Phys. 89, 015003 (2017)]; still, calculations often employ two adiabatically screened vertices, which have been proposed as a reliable approximation for self-energy differences [Phys. Rev. B 82, 165111 (2010)]. We assess the accuracy of both approaches in estimating the phonon spectral functions of model Hamiltonians and the adiabatic low-temperature phonon dispersions of monolayer TaS$_2$ and doped MoS$_2$. We find that the approximate method yields excellent corrections at low computational cost, due to its designed error cancellation to first order, while using a bare vertex could in principle improve these results but is challenging in practice. We offer an alternative strategy based on downfolding to partially screened phonons and interactions [Phys. Rev. B 92, 245108 (2015)]. This is a natural scheme to include electron-electron interactions and tackle phonons in strongly correlated materials and the frequency dependence of the electron-phonon vertex.
