The engineering of the optical response of materials is a paradigm that demands microscopic-level accuracy and reliable predictive theoretical tools. Here we compare and contrast the dispersive permittivity tensor, using both a low-energy effective model and density functional theory (DFT). As a representative material, phosphorene subject to strain is considered. Employing a low-energy model Hamiltonian with a Green's function current-current correlation function, we compute the dynamical optical conductivity and its associated permittivity tensor. For the DFT approach, first-principles calculations make use of the first-order random phase approximation. Our results reveal that although the two models are generally in agreement within the low-strain and low-frequency regime, the intricate features associated with the fundamental physical properties of the system and optoelectronics devices implementation such as band gap, Drude absorption response, vanishing real part, absorptivity, and sign of permittivity over the frequency range show significant discrepancies. Our results suggest that the random phase approximation employed in widely used DFT packages should be revisited and improved to be able to predict these fundamental electronic characteristics of a given material with confidence. Furthermore, employing the permittivity results from both models, we uncover the pivotal role that phosphorene can play in optoelectronics devices to facilitate highly programable perfect absorption of electromagnetic waves by manipulating the chemical potential and exerting strain and illustrate how reliable predictions for the dielectric response of a given material are crucial to precise device design.

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DFT 随机相位近似与低能量有效模型的光学响应比较：应变磷烯

材料的光学响应工程是一种需要微观精度和可靠的预测理论工具的范式。在这里，我们使用低能量有效模型和密度泛函理论 (DFT) 来比较和对比色散介电常数张量。作为代表性材料，考虑了经受应变的磷烯。采用具有格林函数电流-电流相关函数的低能量模型哈密顿量，我们计算动态光导率及其相关的介电常数张量。对于 DFT 方法，第一性原理计算使用一阶随机相位近似。我们的结果表明，虽然这两种模型在低应变和低频范围内通常是一致的，与系统和光电子器件实现的基本物理特性相关的复杂特征，如带隙、德鲁德吸收响应、实部消失、吸收率和频率范围内的介电常数符号显示出显着差异。我们的结果表明，应该重新审视和改进广泛使用的 DFT 封装中采用的随机相位近似，以便能够自信地预测给定材料的这些基本电子特性。此外，采用两种模型的介电常数结果，