Ultrafast light-induced strain and symmetry breaking in ferroic materials

The understanding of the lattice dynamics in ferroic compounds driven by an ultrashort light pulse is an exciting research direction due to the exceptional non-linear properties (optical, elastic, electric and magnetic) of ferroic and multiferroic materials. Photo-induced strain in ferroic materials is driven by a complex interplay between charge, phonon and spin dynamics with microscopic mechanisms that still need to be elucidated. We present recent experiments where ultrafast photoinduced strain is evaluated in BiFeO3-based multiferroic materials, with a focus on the description of the ultrafast symmetry change of the unit-cell that appears after an ultrashort laser pulse. A combination of optical and X-ray time-resolved techniques will be presented. We show that it is possible to modulate at the picosecond time scale the ferroic order by playing with the out-of-plane and in-plane light-induced strains. These new results provide new insights for the understanding of the physics of photo-induced strain, in relation with the light-induced ferroelectric modulation in nanostructured ferroic compounds and could be the first step towards their use as on-purpose ferroic architectures in devices like actuators or modulators with ultra-short light pulses.