使用声子插值法对缺陷的电子 - 声子谱函数进行第一性原理计算
First-principles calculation of electron-phonon spectral functions for defects using phonon interpolation
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中文总结 AI 辅助
研究宽带隙半导体点缺陷中电子 - 声子谱函数，提出基于重构跃迁诱导力的声子插值法，通过在大超胞中对角化插值动力学矩阵恢复相关结构，在金刚石氮空位中心验证该方法，获高分辨率谱密度及相关结构。
中文摘要 AI 辅助
宽带隙半导体中的点缺陷表现出受电子 - 声子耦合强烈影响的光谱，但相应声子边带的直接第一性原理计算常受限于从头算电子结构代码可处理的最大缺陷超胞粗糙的振动谱。本文提出一种声子插值方法，用于在通过在任意密集的声子\(q\)点网格上扩展含缺陷超胞创建的超胞上计算黄 - 里斯谱密度和光学线形函数。该方法基于重构与光激发相关的跃迁诱导力，并利用此局部力源将缺陷跃迁与密集采样的振动连续体耦合。通过在大超胞中对角化插值动力学矩阵恢复长波长声学模式和主体声子谱的详细结构。在金刚石中带负电的氮空位中心的基态\(^{3}A_{2}\)和激发态\(^{3}E\)之间验证了该方法，展示了跃迁力在缺陷周围强烈局域化，在密度泛函理论计算可达的\(4\times4\times4\)超胞中获得收敛的局域化度量。在高达\(32\times32\times32\)（约1700万个原子）的超胞上插值电子 - 声子耦合，从而恢复具有超细光谱分辨率的平滑、连续的黄 - 里斯谱密度。发现主导耦合带出现在63 meV附近，低能声学贡献遵循预期的线性缩放，并恢复了实验中观察到的光学声子区域中与范霍夫相关的更精细结构。
英文摘要
Point defects in wide-band-gap semiconductors exhibit optical spectra strongly shaped by electron-phonon coupling, but direct first-principles calculation of the corresponding phonon sidebands is often limited by the coarse vibrational spectrum of the largest defect supercells accessible by ab-initio electronic structure codes. In this work, we present a phonon-interpolation method for Huang-Rhys spectral densities and optical lineshape functions on hypercells created by extending the defect-containing supercells on arbitrarily dense phonon $q$-point grids. The method is based on reconstructing the transition-induced force associated with the optical excitation and using this localized force source to couple the defect transition to a densely sampled vibrational continuum. In this formulation, the local defect physics is obtained from ab initio supercell calculations, while the long-wavelength acoustic modes and the detailed structure of the host phonon spectrum are recovered by diagonalizing interpolated dynamical matrices in large hypercells. We demonstrate the method on the negatively charged nitrogen-vacancy centre in diamond between its ground $^{3}A_{2}$ and excited $^{3}E$ states. The transition-force is shown to be strongly localized around the defect, with converged localization measures obtained in a $4\times4\times4$ supercell accessible by density functional theory calculations. We interpolate the electron-phonon coupling on hypercells up to $32\times32\times32$ corresponding to approximately 17 million atoms, thereby recovering smooth, continuous Huang-Rhys spectral densities with ultrafine spectral resolution. The dominant coupling band is found near 63~meV; the low-energy acoustic contribution follows the expected linear scaling; and we recover the finer van-Hove-related structures in the optical phonon regime observed in experiments.
