Andrea Cavalleri

Abstract:

Coherent lattice vibrations are excited and probed with pulses of 10 fs duration in LaMnO(3). The measured frequencies correspond to those of Jahn-Teller stretching and of out-of phase rotations of the oxygen octahedra. Surprisingly, the amplitude and damping rate of both modes exhibit a sharp discontinuity at the Néel temperature, highlighting nontrivial coupling between light, lattice, and magnetic structure. We explain this effect by applying the Goodenough-Kanamori rules to the excited state of LaMnO(3), and note that charge transfer can invert the sign of the semicovalent exchange interaction, which in turn perturbs the equilibrium bond lengths.

Abstract:

The observation that atomic disorder emerges exceptionally fast during laser-induced melting of crystalline bismuth prompts fresh thinking about the nature of this phase transition. © 2009 Macmillan Publishers Limited. All rights reserved.

Abstract:

The temporal resolution of existing streak cameras are limited by electron transit time dispersion. Here we present a state-of-art design compensating this to achieve a breakthrough of 100fs time resolution. © 2009 OSA/CLEO/IQEC 2009.

Abstract:

The temporal resolution of existing streak cameras are limited by electron transit time dispersion. Here we present a state-of-art design compensating this to achieve a breakthrough of 100fs time resolution. © 2009 OSA/CLEO/IQEC 2009.

Abstract:

We use sub-10 fs laser pulses in the visible and near IR region of the spectrum in order to probe the dynamics of photo-induced phase transitions on their characteristic timescales. We present results from two different cases: the 1D organic Mott insulator ET-F2TCNQ and the more complex, colossal magneto-resistive manganite, Pr0.7Ca0.3MnO 3. For the former, we find that the melting of the Mott state takes 20 fs, a timescale which is dictated by the electron tunnelling time, h/t. In comparison, the dynamics of the manganite show coupling to a 14 THz structural mode and a high frequency 30 THz mode, which we assign as an orbiton, a collective electronic excitation. © 2009 IOP Publishing Ltd.