Photo-domino effect observed in a perovskite-type cobalt oxide

Optical phase control of the electric, magnetic, and elastic properties of materials by laser irradiation can also be used for ultrafast switching of devices.

However, the real space observation of the photo-induced phase change and resultant dynamics have not been fully investigated, Now, Yoichi Okimoto and his coworkers at the Department of Materials Science at Tokyo Tech focused on a perovskite-type cobaltite --Pr_0.5Ca_0.5CoO₃--as a novel photoactive material for femtosecond reflection spectroscopy using femtosecond laser pulses.

The researchers numerically analyzed the experimental data on the picosecond time scale by exactly solving Maxwell's equations for the material after the photo-irradiation. The results showed that the observed time dependence of reflectance changes resulted from the self-propagation of a photonically created metallic domain at the velocity of the sound wave, as schematically shown in the figure.

Further analyses also indicated that the domain speed could be controllable by changing the pumping fluence and, more importantly, that the photo-conversion ratio was estimated as being approximately 80 Co-sites per single photon.

Such a domino-like propagation is critical for the realization of high efficiency in the optical switching.

Reference:

Authors:	Yoichi Okimoto et al.
Title of original paper:	Ultrasonic Propagation of a Metallic Domain in Pr0.5Ca0.5CoO3 Undergoing a Photoinduced Insulator-Metal Transition
Journal, volume, pages and year:	Physical Review Letters 103, 027402 (2009).
Digital Object Identifier (DOI):	10.1103/PhysRevLett.103.027402
Affiliations:	Department of Materials Science, Tokyo Institute of Technology
Laboratory website:	Koshihara Okimoto Lab

Schematics of the time evolution of the photonically created region.
The yellow regions show the photo-induced metallic area which propagates along z with time evolution.

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Updated January 31: Referenced paper (Acceleration of domain wall movement by photoirradiation in perovskite-type cobaltite)