Modulation of Oxygen Vacancy on Midinfrared Light-Induced Ferroelectricity of KTaO3

Nonlinear phononics plays an important role in intense laser-solid interactions, especially in light-induced superconductivity, polarized and ferroelectric phases. Herein, by nonlinear coupling of phonon modes, the modulation of oxygen vacancy defects on the dynamic properties of midinfrared light-induced ferroelectricity of cubic KTaO3 is studied. It is found that oxygen vacancy causes the coupling constant l between the high-frequency phonon mode and the low-frequency phonon mode to be negative, which means that the lowest frequency infrared-active phonon mode (Q(lz)) is softened when highest-frequency infrared-active phonon mode (Q(hx)) is exteriorly pumped; it is proved that the Q(lz) mode can be softened when the KTaO3 contains 1/8, 1/4, and 2/3 of oxygen vacancies. When the KTaO3 contains a quarter of oxygen vacancies, it can effectively enhance the coupling constant, reduce the damping effect, and induce the ferroelectricity of KTaO3. But the Q(lz) mode cannot be softened when there are 3/8 of oxygen vacancies in KTaO3. Overall, the findings strongly support that turning the photoinduced ferroelectricity of KTaO3 by oxygen vacancy defects is desirable, which provides an effective strategy for controlling the light-induced ferroelectricity in the all-optical devices.