Attosecond Time-Domain Measurement of Core-Level-Exciton Decay in Magnesium Oxide
Attosecond Time-Domain Measurement of Core-Level-Exciton Decay in Magnesium Oxide
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DOI：
10.1103/physrevlett.124.207401
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发表时间：
2020-05-21
影响因子：
8.6
通讯作者：
Leone, Stephen R.
中科院分区：
文献类型：
--
作者：
Geneaux, Romain;Kaplan, Christopher J.;Leone, Stephen R.
用极紫外脉冲激发离子固体产生局部化的芯能级激子，其在某些情况下强烈地耦合到晶格。本文利用阿秒瞬态反射谱在时域内研究了氧化镁的L-2、L-3边的芯能级激子态。阿秒脉冲触发这些短寿命准粒子的激发，其衰变受到时间延迟的近红外脉冲的干扰。结合一个少态理论模型，这表明，红外脉冲移动的明亮（偶极允许）的核心水平激子状态的能量，以及诱导的功能所产生的暗核心水平激子。我们报告的相干寿命为2.3 +/- 0.2和1.6 +/- 0.5 fs的两个最低的核心级激子，并表明，这些主要是强激子-声子耦合的后果，揭示了在这个超快弛豫过程中的结构效应的巨大影响。
Excitation of ionic solids with extreme ultraviolet pulses creates localized core-level excitons, which in some cases couple strongly to the lattice. Here, core-level-exciton states of magnesium oxide are studied in the time domain at the Mg L-2,L-3 edge with attosecond transient reflectivity spectroscopy. Attosecond pulses trigger the excitation of these short-lived quasiparticles, whose decay is perturbed by time-delayed near-infrared pulses. Combined with a few-state theoretical model, this reveals that the infrared pulse shifts the energy of bright (dipole-allowed) core-level-exciton states as well as induces features arising from dark core-level excitons. We report coherence lifetimes for the two lowest core-level excitons of 2.3 +/- 0.2 and 1.6 +/- 0.5 fs and show that these are primarily a consequence of strong exciton-phonon coupling, disclosing the drastic influence of structural effects in this ultrafast relaxation process.