非平衡瞬时近似与偶极禁阻的d-d跃迁
Non-Equilibrium Instantaneous Approximation and Dipole Forbidden d-d Transitions
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中文总结 AI 辅助
本研究提出非平衡瞬时近似方法，结合Hubbard I动力学平均场构造，推导偶极禁阻d-d跃迁的有效耦合，应用于FePS₃的计算重现了时间分辨光电子能谱实验的主要特征。
中文摘要 AI 辅助
时间分辨角分辨光电子能谱可直接探测泵浦诱导的关联材料电子结构变化，但其理论描述通常需要计算量巨大的双时非平衡计算。我们针对泵浦驱动的关联系统提出一种瞬时近似方法，该方法基于格林函数在相对时间变量中的快速衰减与其在平均时间中的较慢演化的分离。结合Hubbard I水平的单次动力学平均场构造，该方法将局域关联壳层的驱动动力学纳入晶格格林函数，同时保留动量分辨率。我们还推导了名义上偶极禁阻的d-d激发的有效耦合，其源于偶极允许的d-p跃迁后接p-d杂化；超出瞬时极限时，同一过程会对光学响应产生依赖能量的顶点修正。作为原理验证，我们将该框架应用于顺磁和反磁性FePS₃，使用密度泛函理论导出的紧束缚模型结合超胞展开方法，计算得到的动量分辨光谱重现了近期时间分辨光电子能谱实验中第一和第二次d-d跃迁激发后观测到的主要定性特征。
英文摘要
Time- and angle-resolved photoemission spectroscopy provides direct access to pump-induced changes in the electronic structure of correlated materials, but its theoretical description generally requires computationally demanding two-time non-equilibrium calculations. We introduce an instantaneous approximation for pump-driven correlated systems, based on a separation between the rapid decay of the Green's functions in the relative time variable and their slower evolution in the average time. Combined with a one-shot dynamical mean-field construction at the Hubbard I level, the method incorporates the driven dynamics of the local correlated shell into the lattice Green's function while retaining momentum resolution. We also derive an effective coupling for nominally dipole-forbidden d-d excitations. It arises from a dipole-allowed d-p transition followed by p-d hybridization; beyond the instantaneous limit, the same process produces an energy-dependent vertex correction to the optical response. As a proof of principle, we apply the framework to paramagnetic and antiferromagnetic FePS3, using a density-functional theory derived tight-binding model together with a supercell unfolding procedure. The calculated momentum-resolved spectra reproduce the main qualitative features observed after excitation of the first and second d-d transitions in recent time-resolved photoemission experiments.
发表机构
- TU Dortmund University（多特蒙德工业大学）
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