Photo-induced insulator-to-metal transition and coherent acoustic phonon propagation in LaCoO${}_3$ thin films explored by femtosecond pump-probe ellipsometry

Abstract

We have studied ultrafast dynamics of thin films of LaCoO${}_3$ and La${}_{0.5}$Sr${}_{0.5}$CoO${}_3$ with femtosecond pump-probe ellipsometry in the energy range of 1.6-3.4 eV. We have observed a large pump-induced transfer of spectral weight in LaCoO${}_3$ that corresponds to an insulator-to-metal transition. The photo-induced metallic state initially relaxes via a fast process with a decay constant of about 200 fs. Both LaCoO${}_3$ and La${}_{0.5}$Sr${}_{0.5}$CoO${}_3$ exhibit a significant secondary transient structure 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 modelled with a bi-exponential decay.

arXiv comment8 pages, 4 figures

References in corpus (13)

• The spin state transition in LaCoO${}_3$; revising a revision
• Evidence for a Low-Spin to Intermediate-Spin State Transition in LaCoO3
• Spin-state transition in LaCoO3: direct neutron spectroscopic evidence of excited magnetic states
• Soft x-ray magnetic circular dichroism of LaCoO${}_3$, La${}_{0.7}$Ce${}_{0.3}$CoO${}_3$, and La${}_{0.7}$Sr${}_{0.3}$CoO${}_3$ films: Evidence for Co valency-dependent magnetism and magnetic anisotropy
• The 5D term origin of the excited triplet in LaCoO3
• Spin state transition and covalent bonding in LaCoO3
• Ultrafast dynamics of hot charge carriers in an oxide semiconductor probed by femtosecond spectroscopic ellipsometry
• Dimensionality Control of d-orbital Occupation in Oxide Superlattices
• Magnetic properties of RCoO${}_3$ cobaltites (R = La, Pr, Nd, Sm, Eu). Effects of hydrostatic and chemical pressure
• Two Component Heat Diffusion Observed in CMR Manganites
• Direct observation of double exchange in ferromagnetic La${}_{0.7}$Sr${}_{0.3}$CoO${}_3$ by broadband ellipsometry
• Coherent optical and acoustic phonons generated at lattice-matched GaP/Si(001) heterointerfaces
• Damping of spinful excitons in LaCoO${}_3$ by thermal fluctuations: Theory and experiment

Cited by in corpus (1)

• Optical signatures of strain-induced ferromagnetism in LaCoO${}_3$ thin film