Temperature dependence of the photoinduced dynamics on the cleaved surface of BaV₁₀O₁₅

The temperature dependence of the photoinduced dynamics by the irradiation of a femtosecond laser pulse was studied for the cleaved surface of BaV ₁₀O₁₅, which shows V trimerization with orbital ordering at Tc = 123 K. For T > Tc , the photoinduced reflectivity change exhibits oscillation with time, indicating that a photoinduced state propagates with time in the crystal. For T < Tc, almost time-independent behavior after the instantaneous change of the reflectivity is observed over several tens of picoseconds, indicating the appearance of a stable photoinduced phase. The different photoinduced dynamics above and below Tc can be attributed to the absence or existence of V trimerization with orbital ordering. We also found that the absolute values of the photoinduced reflectivity change are several times larger on the cleaved surface than those on the polished surface, indicating that remnant stress on the polished surface affects the photoinduced dynamics.