Abstract
We study the ultrafast phonon response of mixed-valence perovskite CsAuI 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 Au of less than 4 ps, which is an indication of the local character of the Au 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.
- Received 28 December 2011
DOI:https://doi.org/10.1103/PhysRevB.85.081102
©2012 American Physical Society