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

S. Borroni, E. Baldini, V. M. Katukuri, A. Mann, K. Parlinski, D. Legut, C. Arrell, F. van Mourik, J. Teyssier, A. Kozlowski, P. Piekarz, O. V. Yazyev, A. M. Oleś, J. Lorenzana, and F. Carbone
Phys. Rev. B 96, 104308 – Published 19 September 2017
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Abstract

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 (Fe3O4) 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.

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  • Received 3 March 2017

DOI:https://doi.org/10.1103/PhysRevB.96.104308

©2017 American Physical Society

Physics Subject Headings (PhySH)

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

S. Borroni1, E. Baldini1,2, V. M. Katukuri3, A. Mann1, K. Parlinski4, D. Legut5, C. Arrell2, F. van Mourik2, J. Teyssier6, A. Kozlowski7, P. Piekarz4, O. V. Yazyev3, A. M. Oleś8, J. Lorenzana9, and F. Carbone1,*

  • 1Laboratory for Ultrafast Microscopy and Electron Scattering and the Lausanne Centre for Ultrafast Science, IPHYS, École Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland
  • 2Laboratory for Ultrafast Spectroscopy and the Lausanne Centre for Ultrafast Science, ISIC, École Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland
  • 3Chair of Computational Condensed Matter Physics, IPHYS, École Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland
  • 4Institute of Nuclear Physics, Polish Academy of Sciences, 31-342 Kraków, Poland
  • 5IT4Innovations Center, VSB-Technical University of Ostrava, 17.listopadu 15, 708 33 Ostrava, Czech Republic
  • 6Department of Quantum Matter Physics, University of Geneva, CH-1211 Geneva, Switzerland
  • 7Faculty of Physics and Applied Computer Science, AGH-University of Science and Technology, Aleja Mickiewicza 30, PL-30059 Kraków, Poland
  • 8Marian Smoluchowski Institute of Physics, Jagiellonian University, prof. S. Lojasiewicza 11, PL-30348 Kraków, Poland
  • 9Institute for Complex Systems–CNR, and Physics Department, University of Rome “La Sapienza,” I-00185 Rome, Italy

  • *Corresponding author: fabrizio.carbone@epfl.ch.

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Issue

Vol. 96, Iss. 10 — 1 September 2017

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