Suppression of Exciton Condensation in Copper-Doped TiSe<sub>2</sub> Measured with M-EELS

ORAL

Abstract

Excitons were predicted to form a Bose condensate, but for many years there was no direct experimental verification of this condensation in a solid. Using momentum-resolved electron energy-loss spectroscopy (M-EELS), we demonstrated the presence of an exciton condensate in 1T-TiSe2 by observing a soft electronic collective mode at the charge density wave (CDW) transition temperature, TC = 190 K. As TiSe2 is doped with copper to form CuxTiSe2, the CDW transition temperature is suppressed and a superconducting dome emerges around x = 0.04. Using M-EELS, we found that the electronic collective mode softens partially near TC for very low dopings (x < 0.004), but does not soften above x ~ 0.01. Our results indicate that the exciton condensate is rapidly destroyed in CuxTiSe2 by screening from the Cu atoms and that a conventional Peierls CDW persists above x ~ 0.01. We conclude that the excitonic state is not directly related to the superconductivity in CuxTiSe2.

*This work was supported by the Gordon and Betty Moore Foundation's EPiQS Initiative through Grant GBMF-4542.

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Presenters

  • Melinda Rak

    • University of Illinois at Urbana-Champaign
    • Department of Physics and Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign

Authors

  • Melinda Rak

    • University of Illinois at Urbana-Champaign
    • Department of Physics and Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign

  • Samantha Rubeck

    • University of Illinois at Urbana-Champaign
    • Department of Physics and Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign

  • Matteo Mitrano

    • University of Illinois at Urbana-Champaign
    • Department of Physics and Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign
    • Physics, University of Illinois at Urbana-Champaign

  • Ali Husain

    • University of Illinois at Urbana-Champaign
    • Department of Physics and Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign
    • Physics, University of Illinois at Urbana-Champaign

  • Anshul Kogar

    • Physics, Massachusetts Institute of Technology
    • Massachusetts Institute of Technology

  • Sean Vig

    • University of Illinois at Urbana-Champaign

  • Jasper Van Wezel

    • Institute for Theoretical Physics, Institute of Physics, University of Amsterdam
    • University of Amsterdam
    • Institute of Theoretical Physics, University of Amsterdam

  • Goran Karapetrov

    • Department of Physics, Drexel University
    • Drexel University
    • Physics, Drexel University

  • Emilia Morosan

    • Rice University
    • Physics and Astronomy, Rice University
    • Department of Physics and Astronomy, Rice University

  • Peter Abbamonte

    • University of Illinois, Urbana-Champaign
    • University of Illinois at Urbana-Champaign
    • Department of Physics and Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign