"Ultrafast pump-probe measurements of short small-polaron lifetimes in the mixed-valence perovskite Cs2Au2I6 under high pressures"

Trigo, M.: Chen, J., Jiang, M. P., Mao, W. L., Riggs, S. C., Shapiro, M. C., Fisher, I. R., Reis, D. A.; Physical Review B, 02/03/12.

Additional Authors: Chen, J., Jiang, M. P., Mao, W. L., Riggs, S. C., Shapiro, M. C., Fisher, I. R., Reis, D. A.

Abstract:

We study the ultrafast phonon response of mixed-valence perovskite Cs2Au2I6 using pump-probe spectroscopy under high pressure in a diamond-anvil cell. We observed a remarkable softening and broadening of the Au-I stretching phonon mode with both applied pressure and photoexcitation. Using a double-pump scheme we measured a lifetime of the charge-transfer excitation into single-valence Au2+ of less than 4 ps, which is an indication of the local character of the Au2+ excitation. Furthermore, the strong similarity between the pressure and fluence dependence of the phonon softening shows that the intervalence charge transfer plays an important role in the structural transition.