Ultrafast real space dynamics of photoexcited state in a layered perovskite-type spin crossover oxide La1.5Sr0.5CoO 4

Yoichi Okimoto, Tsugumi Egawa, Ryo Fukaya, Yoshitaka Matsubara, Yuki Yamada, Nao Yamaya, Tadahiko Ishikawa, Ken Onda, Shin Ya Koshihara, Hiroki Taniguchi, Mitsuru Itoh, Akira Isayama, Takao Sasagawa

研究成果: Contribution to journalArticle査読

8 被引用数 (Scopus)


Ultrafast optical responses were investigated using a fs laser system on a layered perovskite-type cobalt oxide, La1.5Sr0.5CoO 4 with a checkerboard-type charge ordering. To investigate the spatial variation of the photoexcited state, we measured the transient changes of three independent optical quantities, i.e., transmittance, reflectivity, and backside reflectivity, as well as their fluence dependence at 0.25 eV. Using the numerical calculations based on Maxwell's equations, we calculated not only the dielectric constant but also the decay length of the photoexcited region (L) and analyzed the real-space dynamics of the photoexcited area in terms of the fluence and time dependence of L. With the above information on the time dependence of L and Kramers-Kronig analysis, we numerically calculated the transient optical conductivity spectra, which showed instantaneous formation of a polaron-like absorption peak in the midinfrared region. A 10 fs pump-probe reflection measurement revealed that the photoexcited state occurs within the time resolution (≈10 fs). The time profile of the reflectivity is accompanied with an oscillation assigned as a breathing phonon mode in the CoO2 layer observed in Raman spectroscopy. Analyses of the decay time and the frequency revealed that the photoirradiation melted the charge ordering in La1.5Sr0.5CoO4.

ジャーナルjournal of the physical society of japan
出版ステータス出版済み - 7 2013

All Science Journal Classification (ASJC) codes

  • 物理学および天文学(全般)


「Ultrafast real space dynamics of photoexcited state in a layered perovskite-type spin crossover oxide La<sub>1.5</sub>Sr<sub>0.5</sub>CoO <sub>4</sub>」の研究トピックを掘り下げます。これらがまとまってユニークなフィンガープリントを構成します。