Photoinduced insulator-to-metal transition and coherent acoustic phonon propagation in LaCoO3 thin films explored by femtosecond pump-probe ellipsometry

• Autoři: ZAHRADNÍK Martin; KIABA Michal; ESPINOZA Shirly; REBARZ Mateusz; ANDREASSON Jakob; CAHA Ondřej; ABADIZAMAN Farzin; MUNZAR Dominik; DUBROKA Adam
• Rok publikování: 2022
• Druh: Článek v odborném periodiku
• Časopis / Zdroj: Physical Review B
• Fakulta / Pracoviště MU: Přírodovědecká fakulta
• www: https://journals.aps.org/prb/abstract/10.1103/PhysRevB.105.235113
• Doi: http://dx.doi.org/10.1103/PhysRevB.105.235113
• Klíčová slova: Carrier dynamics; Heat transfer; Lifetimes & widths; Metal-insulator transition; Optical conductivity
• Popis: We have studied ultrafast dynamics of thin films of LaCoO3 and La0.5Sr0.5CoO3 with femtosecond pumpprobe ellipsometry in the energy range of 1.6???3.4 eV. We have observed a large pump-induced transfer of spectral weight in LaCoO3 that corresponds to an insulator-to-metal transition. The photoinduced metallic state initially relaxes via a fast process with a decay constant of about 200 fs. Both LaCoO3 and La0.5Sr0.5CoO3 exhibit a significant secondary peak in the 1???30 ps range. Results of measurements on films with different thicknesses demonstrate that it corresponds to a propagation of an acoustic strain pulse. On timescales longer than 100 ps, heat diffusion to the substrate takes place that can be modeled with a biexponential decay.

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