Attosecond time-domain measurement of core-excitonic decay in magnesium oxide

• Published in: arXiv.org 2019-12
• Main Authors: Géneaux, Romain, Kaplan, Christopher J, Lun Yue, Ross, Andrew D, Bækhøj, Jens E, Kraus, Peter M, Chang, Hung-Tzu, Guggenmos, Alexander, Mi-Ying, Huang, Zürch, Michael, Schafer, Kenneth J, Neumark, Daniel M, Gaarde, Mette B, Leone, Stephen R
• Format: Article
• Language: English
• Subjects: Attosecond pulses; Decay; Excitation; Excitons; Magnesium oxide; Optical pulses; Superconductors (materials); Time domain analysis
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.1912.12266

Excitation of ionic solids with extreme ultraviolet pulses creates localized core-excitons, which in some cases couple strongly to the lattice. Here, core-excitonic states of magnesium oxide are studied in the time domain at the Mg \(\text{L}_{2,3}\) 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 optical pulses. Combined with a few-state theoretical model, this reveals that the optical pulse shifts the energy of bright core-exciton states as well as induces features arising from dark core-excitons. We report coherence lifetimes for the first two core-excitons of \(2.3 \pm 0.2\) and \(1.6 \pm 0.5\) femtoseconds and show that these short lifetimes are primarily a consequence of strong exciton-phonon coupling, disclosing the drastic influence of structural effects in this ultrafast relaxation process.