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Sunday, June 18, 2017
Abstract-Ultrafast Control of the Polarity of BiCoO 3 by Orbital Excitation as Investigated by Femtosecond Spectroscopy
Y. Okimoto, S. Naruse, R. Fukaya, T. Ishikawa, S. Koshihara, K. Oka, M. Azuma, K. Tanaka, and H. Hirori
Phys. Rev. Applied 7, 064016 – Published 12 June 2017
https://journals.aps.org/prapplied/abstract/10.1103/PhysRevApplied.7.064016 BiCoO3 is a perovskite-type cobalt oxide with a polar structure. We investigate the dynamics of its polar state by using photoexcitation with femtosecond visible and terahertz pulses. The intensity of the second-harmonic light, caused by a polar structure without inversion symmetry, is enhanced by more than 50% by irradiating the terahertz pulse showing an ultrafast response following the femtosecond terahertz pulse. By contrast, it is suppressed by more than 60% by exciting visible light with a 100-fs pulse width at room temperature. These results suggest not only an important role of the orbital excitation in the Co3+ ion but also a key to improving the nonlinear optical response, e.g., a figure of merit in nonlinear crystals on the time scale of a femtosecond.