Dynamics of photoinduced phenomena in AV ₁₀O ₁₅ (A = Ba, Sr)

We studied the dynamics of photoinduced phenomena in AV ₁₀O ₁₅ (A=Ba, Sr), where the ground state changes from an insulating state with V trimerization (Ba) to another insulating state with no structural anomaly (Sr). We found that the time dependence of photoinduced reflectivity change is similar up to several picoseconds, but is critically different in the range of several tens of picoseconds between the two compounds. These different behaviors can be attributed to the coupled mode of the photoexcited electronic state and the lattice distortion, which propagates in the crystal of SrV ₁₀O ₁₅ but is trapped in the local minimum of the free energy in BaV ₁₀O ₁₅.