Coupling Among Carriers and Phonons in Femtosecond Laser Pulses Excited SrRuO₃: A Promising Candidate for Optomechanical and Optoelectronic Applications

Large reversible lattice strain that manipulates coupled degrees of freedom can be induced by optics in SrRuO3, suggesting it has great potential in optomechanical and optoelectronic devices. Photoexcitation and energy transfer via electron–phonon scattering have been studied, but recent studies inferred that more processes that remain to be identified contribute to the light-induced deformation. Here, by combining ultrafast X-ray diffraction and ultrafast optical reflectivity experiments, we image the excitation and relaxation characteristics of SrRuO3 films. Upon photoexcitation, photocarriers redistribute both in space and energy and then relax with fast direct recombination, phonon-assisted relaxation and phonon–phonon scattering dominating on a longer time scale. The phonon-assisted relaxation process, together with the thermal effect resulting from the electron–phonon scattering on sub-picosecond time scales, contributes to the photoinduced strain in SrRuO3. Phonon and electron effects on relaxations of SrRuO3 are studied, including the bottleneck effects of phonons on the coupled carrier and phonon relaxation and the scaled relationship of the fast carrier relaxation with the electron correlation. Our results suggest optomechanical and optoelectronic manipulations of SrRuO3 by electronic pumping, providing avenues for designs of applications with high performance.