Discovery of the soft electronic modes involved in magnetite’s Verwey transition

ORAL

Abstract

The Verwey transition in magnetite (Fe3O4), the first metal-insulator transition ever observed, is accompanied by charge ordering, orbital ordering, and a structural rearrangement. Due to the intricate interplay of these degrees of freedom, a complete understanding of the microscopic mechanism of this transition to the exotic low-temperature phase has not yet been reached. Recently, the charge-ordered structure was established as a network of small polarons extending across three sites, termed trimerons. However, the dynamics of the Verwey transition from an electronic point of view remains not understood, as no collective excitations of this trimeron order have been observed to date. In this talk, I will present our discovery of spectroscopic signatures of the low-energy electronic modes of the trimeron network using terahertz light. By exciting these collective modes coherently with an ultrashort laser pulse, we unveil their softening towards the transition temperature. These findings represent the first observation of collective modes of any sort displaying a critical softening in magnetite and thus shed light on the long-sought cooperative mechanism responsible for the Verwey transition.

*U.S. Department of Energy, Gordon and Betty Moore Foundation, National Science Foundation

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Presenters

  • Carina Belvin

    • Massachusetts Institute of Technology MIT

Authors

  • Carina Belvin

    • Massachusetts Institute of Technology MIT

  • Edoardo Baldini

    • Massachusetts Institute of Technology MIT

  • Martin Rodriguez-vega

    • Physics, University of Texas at Austin
    • The University of Texas at Austin
    • Center for Dynamics and Control of Materials, University of Texas at Austin
    • University of Texas at Austin

  • Ilkem Ozge Ozel

    • Massachusetts Institute of Technology MIT

  • Dominik Legut

    • VSB-Technical University of Ostrava

  • Andrzej Kozlowski

    • AGH-University of Science and Technology

  • Andrzej Oles

    • Institute of Theoretical Physics, Jagiellonian University, Krakow, Poland
    • Institute of Theoretical Physics, Jagiellonian University, Kraków, Poland
    • Max Planck Institute for Solid State Research

  • Krzysztof Parlinski

    • Polish Academy of Sciences

  • Przemyslaw Piekarz

    • Institute of Nuclear Physics Polish Academy of Sciences, Krakow, Poland
    • Institute of Nuclear Physics Polish Academy of Sciences, Kraków, Poland
    • Polish Academy of Sciences

  • Josee Lorenzana

    • University of Rome La Sapienza
    • Dipartimento di Fisica, Consiglio Nazionale delle Ricerche

  • Gregory Fiete

    • Physics, Northeastern University
    • Northeastern University
    • Physics Department, Northeastern University
    • Department of Physics, Northeastern University

  • Nuh Gedik

    • Massachusetts Institute of Technology MIT
    • Massachusetts Institute of Technology