自旋缺陷振动结构的第一性原理累积量方法
First-principles cumulant approach to the vibronic structure of spin defects
AI总结：
本文提出基于推迟累积量假设（RCA）的第一性原理格林函数框架，将其应用于金刚石NV⁻中心，揭示该中心振动结构的各向异性及多声子卫星峰的能量范围，为自旋缺陷振动结构的定量描述提供了新方法。
AI中文摘要：
宽带隙半导体中的色心是固态量子技术的领先平台，但由于局域缺陷态中多声子过程的复杂性，对其振动结构的定量描述一直难以实现。本文提出一种基于推迟累积量假设（RCA）的第一性原理格林函数框架，用于描述自旋缺陷中的电声相互作用，该方法超越了广泛使用的近似方法所基于的绝热近似和最低阶微扰理论。将该方法应用于金刚石中带负电的氮-空位（NV⁻）中心，结果表明，即使在零温度下，多声子卫星峰也会在400 meV的能量窗口内持续存在，这由量子零点涨落驱动。研究还表明，准确的谱函数需要在整个布里渊区采样的模式、动量、自旋和轨道分辨的电声矩阵元，以解释杂化和传播的声子通道。我们发现NV⁻中心的振动结构表现出强自旋和轨道各向异性，不同轨道与声子谱的不同部分耦合，且自旋选择性耦合会影响边带的位置和强度。
英文摘要：
Color centers in wide-band-gap semiconductors are leading platforms for solid-state quantum technologies, yet a quantitative description of their vibronic structure has remained elusive due to the complexity of multi-phonon processes in localized defect states. Here we present a first-principles Green's function framework based on the retarded cumulant ansatz (RCA) to describe electron-phonon interactions in spin defects; our approach goes beyond the adiabatic and lowest-order perturbation theory approximations underlying widely used approaches. Applied to the negatively charged nitrogen-vacancy (NV$^-$) center in diamond, our method reveals that multi-phonon satellites persist over a 400 meV energy window even at zero temperature, driven by quantum zero-point fluctuations. We demonstrate that accurate spectral functions require mode-, momentum-, spin-, and orbital-resolved electron-phonon matrix elements sampled across the full Brillouin zone, to account for hybridized and propagating phonon channels. We find that the vibronic structure of the NV$^-$ center exhibits strong spin and orbital anisotropy, with different orbitals coupling to qualitatively distinct parts of the phonon spectrum, and spin-selective coupling affecting both sideband positions and intensities.
