Quantum embedding methods for correlated excited states of point defects: Case studies and challenges
Quantum embedding methods for correlated excited states of point defects: Case studies and challenges
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DOI：
10.1103/physrevb.105.235104
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发表时间：
2021-05
影响因子：
3.7
通讯作者：
Lukas Muechler;D. I. Badrtdinov;A. Hampel;Jennifer Cano;M. Rösner;C. Dreyer
中科院分区：
文献类型：
--
作者：
Lukas Muechler;D. I. Badrtdinov;A. Hampel;Jennifer Cano;M. Rösner;C. Dreyer
点缺陷和杂质的激发态的定量描述对于理解材料性质和缺陷在量子技术中的可能应用至关重要。这对于计算方法来说是一个相当大的挑战，因为Kohn-Sham密度泛函理论（DFT）本质上是一个基态理论，而更高层次的方法对于缺陷系统来说通常计算成本太高。近年来，采用多体方法处理缺陷状态的嵌入方法，同时使用DFT来描述主体材料。我们基于缺陷轨道的万尼化和约束随机相位近似方法实现了这种嵌入方法，并对当前技术相关的三种不同体系进行了系统的表征：碳二聚体取代块体六方BN中的B和N对（C$_{\text{B}}$C$_{\text{N}}$），金刚石中带负电荷的氮空位中心（NV$^-$），以及在精锌矿AlN中Al位上的铁杂质（$\text{Fe}_{\text{Al}}$）。对于C$_{\text{B}}$C$_{\text{N}}$，我们表明嵌入方法给出的多体状态与哈伯德二聚体模型的分析结果一致，这使我们能够阐明DFT函数和重复计数校正的影响。对于NV$^-$中心，我们的方法与三重态-三重态跃迁的零声子线的实验结果显示了良好的定量一致性。最后，我们说明了用这种方法确定$\text{Fe}_{\text{Al}}$中复杂自旋多重子的能量和顺序所面临的挑战。
A quantitative description of the excited electronic states of point defects and impurities is crucial for understanding materials properties, and possible applications of defects in quantum technologies. This is a considerable challenge for computational methods, since Kohn-Sham density-functional theory (DFT) is inherently a ground state theory, while higher-level methods are often too computationally expensive for defect systems. Recently, embedding approaches have been applied that treat defect states with many-body methods, while using DFT to describe the bulk host material. We implement such an embedding method, based on Wannierization of defect orbitals and the constrained random-phase approximation approach, and perform systematic characterization of the method for three distinct systems with current technological relevance: a carbon dimer replacing a B and N pair in bulk hexagonal BN (C$_{\text{B}}$C$_{\text{N}}$), the negatively charged nitrogen-vacancy center in diamond (NV$^-$), and an Fe impurity on the Al site in wurtzite AlN ($\text{Fe}_{\text{Al}}$). For C$_{\text{B}}$C$_{\text{N}}$ we show that the embedding approach gives many-body states in agreement with analytical results on the Hubbard dimer model, which allows us to elucidate the effects of the DFT functional and double-counting correction. For the NV$^-$ center, our method demonstrates good quantitative agreement with experiments for the zero-phonon line of the triplet-triplet transition. Finally, we illustrate challenges associated with this method for determining the energies and orderings of the complex spin multiplets in $\text{Fe}_{\text{Al}}$.