铅卤化物钙钛矿晶体中明亮-暗态分裂的量子拍现象通过光子回声中的量子拍现象获得
Bright-dark exciton splitting in lead halide perovskite crystals accessed via quantum beats in photon echoes
AI总结：
通过光子回声中的量子拍现象研究铅卤化物钙钛矿晶体中激子的明亮-暗态分裂及其能级结构。
摘要：
理解激子的精细结构对于铅卤化物钙钛矿的光电和量子光子应用至关重要。研究表明，在磁场中使用极化敏感的光子回声光谱技术提供了一种强有力的手段来访问相干激子动力学并揭示其能级结构，这些结构被不均匀展宽所隐藏。在法拉第和沃伊格式中观察到的激子量子拍现象为四种1s激子态之间的能量分裂提供了精确的探测手段，从而能够确定精细结构和明亮-暗态分裂。将该技术应用于体混合卤化物钙钛矿晶体FA₀.₉Cs₀.₁PbI₂.₈Br₀.₂揭示了明亮-暗态分裂Δ_X=0.46 meV，同时电子和空穴兰德g因子g_e=3.38和g_h=-1.14。量子拍现象在20-50 ps的时间尺度上持续存在，表明在2 K的极低温下具有显著的自旋和光学相干性。外双重态量子拍的衰减由由于明亮-暗态分裂的~0.06 meV的色散引起的去相位所支配，而明亮激子内双重态的去相位起源于由于各向异性势能引起的小零场分裂的~0.035 meV。
英文摘要：
Understanding the fine structure of excitons is crucial for optoelectronic and quantum photonic applications of lead halide perovskites. It is demonstrated that polarization-sensitive photon echo spectroscopy in magnetic field provides a powerful method to access coherent exciton dynamics and reveal their energy level structure, which is hidden by inhomogeneous broadening. Exciton quantum beats observed in both Faraday and Voigt geometries offer a precise probe of the energy splittings among the four 1$s$ exciton states, enabling determination of the fine structure and bright-dark splittings. Application of this technique to bulk mixed halide perovskite crystals FA$_{0.9}$Cs$_{0.1}$PbI$_{2.8}$Br$_{0.2}$ reveals a bright-dark exciton splitting of $Δ_\mathrm{X}=0.46~$meV, along with electron and hole Landé $g$ factors $g_\mathrm{e}=3.38$ and $g_\mathrm{h}=-1.14$, respectively. The quantum beats persist on timescales of 20--50$~$ps, demonstrating remarkably robust spin and optical coherences at cryogenic temperature of 2$~$K. The decay of the quantum beats of the outer doublet is governed by dephasing due to dispersion of the bright-dark splitting of $\sim0.06~$meV caused by localization potential fluctuations, while dephasing in the bright exciton inner doublet originates from a small zero field splitting of $\sim0.035~$meV due to anisotropic potentials.
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