Optical spectra of 2D monolayers from time-dependent density functional theory.,Faraday Discussions

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Optical spectra of 2D monolayers from time-dependent density functional theory.
Faraday Discussions ( IF 3.3 ) Pub Date : 2020-07-06 , DOI: 10.1039/d0fd00073f
S Di Sabatino ₁ , J A Berger , P Romaniello

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The optical spectra of two-dimensional (2D) periodic systems provide a challenge for time-dependent density-functional theory (TDDFT) because of the large excitonic effects in these materials. In this work we explore how accurately these spectra can be described within a pure Kohn–Sham time-dependent density-functional framework, i.e., a framework in which no theory beyond Kohn–Sham density-functional theory, such as GW, is required to correct the Kohn–Sham gap. To achieve this goal we adapted a recent approach we developed for the optical spectra of 3D systems [S. Cavo, J. A. Berger and P. Romaniello, Phys. Rev. B, 2020, 101, 115109] to those of 2D systems. Our approach relies on the link between the exchange–correlation kernel of TDDFT and the derivative discontinuity of ground-state density-functional theory, which guarantees a correct quasi-particle gap, and on a generalization of the polarization functional [J. A. Berger, Phys. Rev. Lett., 2015, 115, 137402], which describes the excitonic effects. We applied our approach to two prototypical 2D monolayers, h-BN and MoS₂. We find that our protocol gives a qualitatively good description of the optical spectrum of h-BN, whereas improvements are needed for MoS₂ to describe the intensity of the excitonic peaks.

中文翻译：

基于时变密度泛函理论的二维单层光谱。

二维（2D）周期系统的光谱为依赖于时间的密度泛函理论（TDDFT）提出了挑战，因为这些材料中的激子效应很大。在这项工作中，我们探索如何在纯的Kohn-Sham随时间变化的密度函数框架内准确描述这些光谱，即在该框架中不需要超出Kohn-Sham密度函数理论的任何理论，例如GW，纠正Kohn-Sham差距。为了实现这一目标，我们采用了针对3D系统光谱开发的最新方法[S. Cavo，JA Berger和P.Romaniello，物理学。版本B，2020年，101（115109）适用于2D系统。我们的方法依赖于TDDFT的交换相关核与基态密度泛函理论的导数不连续性之间的联系，后者保证了正确的准粒子间隙，并且依赖于极化泛函的泛化[JA Berger，Phys。牧师 ，2015，115，137402]，其描述了激子的效果。我们将我们的方法应用于两个典型的2D单层，即h-BN和MoS ₂。我们发现我们的协议在质量上很好地描述了h-BN的光谱，而MoS ₂需要改进来描述激子峰的强度。

更新日期：2020-07-06

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