激子的性质,或相关的电子-空穴对,对材料的光电应用至关重要。激子物理学的核心组成部分是电子-空穴相互作用,通常被视为仅由材料中的电子进行屏蔽。然而,核运动也可以筛选这种库仑相互作用,最近的几项研究开发了近似激子性质的声子筛选的模型方法。虽然这些模型方法倾向于提高与实验的一致性,它们依赖于几个近似值,这些近似值限制了它们对广泛材料的适用性,到目前为止,他们忽略了有限温度的影响。这里,我们制定了完整的第一原则,无参数方法在从头算[公式:请参见文本]-Bethe-Salpeter方程框架内计算声子筛选的温度相关效应。我们恢复了以前提出的声子筛选模型,作为我们一般框架的明确定义的限制,并通过将它们与我们的第一原则结果进行比较来讨论它们的有效性。我们开发了高效的计算工作流程,并将其应用于各种半导体,特别是AlN,CdS,GaN,MgO,和[公式:见正文]。我们演示了在不同的物理场景下如何通过多个极性光学或声学声子筛选激子,它们的结合能如何表现出强烈的温度依赖性,以及它们解离成自由电子-空穴对的超快时间尺度。
The properties of
excitons, or correlated electron-hole pairs, are of paramount importance to optoelectronic applications of materials. A central component of exciton physics is the electron-hole interaction, which is commonly treated as screened solely by electrons within a material. However, nuclear motion can screen this Coulomb interaction as well, with several recent studies developing model approaches for approximating the phonon screening of excitonic properties. While these model approaches tend to improve agreement with experiment, they rely on several approximations that restrict their applicability to a wide range of materials, and thus far they have neglected the effect of finite temperatures. Here, we develop a fully first-principles, parameter-free approach to compute the temperature-dependent effects of phonon screening within the ab initio [Formula: see text]-Bethe-Salpeter equation framework. We recover previously proposed models of phonon screening as well-defined limits of our general framework, and discuss their validity by comparing them against our first-principles results. We develop an efficient computational workflow and apply it to a diverse set of semiconductors, specifically AlN, CdS, GaN, MgO, and [Formula: see text]. We demonstrate under different physical scenarios how
excitons may be screened by multiple polar optical or acoustic phonons, how their binding energies can exhibit strong temperature dependence, and the ultrafast timescales on which they dissociate into free electron-hole pairs.