• DOI:10.1103/PHYSREVB.96.104308
• Corpus ID: 119256077

Coherent generation of symmetry-forbidden phonons by light-induced electron-phonon interactions in magnetite

@article{Borroni2015CoherentGO,
  title={Coherent generation of symmetry-forbidden phonons by light-induced electron-phonon interactions in magnetite},
  author={S Borroni and Edoardo Baldini and Vamshi M. Katukuri and Andreas Mann and Krzysztof Parlinski and Dominik Legut and C A Arrell and F. van Mourik and J{\'e}r{\'e}mie Teyssier and A. Kozłowski and Przemysław Piekarz and Oleg V. Yazyev and Andrzej M. Ole's and Jos{\'e} Lorenzana and Fabrizio Carbone},
  journal={Physical Review B},
  year={2015},
  volume={96},
  pages={104308}
}

• S. Borroni, E. Baldini, +12 authors F. Carbone
• Published 26 July 2015
• Physics
• Physical Review B

Symmetry breaking across phase transitions often causes changes in selection rules and emergence of optical modes which can be detected via spectroscopic techniques or generated coherently in pump-probe experiments. In second-order or weakly first-order transitions, fluctuations of the ordering field are present above the ordering temperature, giving rise to intriguing precursor phenomena, such as critical opalescence. Here, we demonstrate that in magnetite $({\mathrm{Fe}}_{3}{\mathrm{O}}_{4})$ light excitation couples to the critical fluctuations of the charge order and coherently generates structural modes of the ordered phase above the critical temperature of the Verwey transition. Our findings are obtained by detecting coherent oscillations of the optical constants through ultrafast broadband spectroscopy and analyzing their dependence on temperature. To unveil the coupling between the structural modes and the electronic excitations, at the origin of the Verwey transition, we combine our results from pump-probe experiments with spontaneous Raman scattering data and theoretical calculations of both the phonon dispersion curves and the optical constants. Our methodology represents an effective tool to study the real-time dynamics of critical fluctuations across phase transitions.