Signatures of exciton condensation in a transition metal dichalcogenide

Anshul Kogar, Melinda S. Rak, Sean Vig, Ali A. Husain, Felix Flicker, Young Il Joe, Luc Venema, Greg J. MacDougall, Tai C. Chiang, Eduardo Fradkin, Jasper Van Wezel, Peter Abbamonte

Research output: Contribution to journalArticle

Abstract

Bose condensation has shaped our understanding of macroscopic quantum phenomena, having been realized in superconductors, atomic gases, and liquid helium. Excitons are bosons that have been predicted to condense into either a superfluid or an insulating electronic crystal. Using the recently developed technique of momentum-resolved electron energy-loss spectroscopy (M-EELS), we studied electronic collective modes in the transition metal dichalcogenide semimetal 1T-TiSe2. Near the phase-transition temperature (190 kelvin), the energy of the electronic mode fell to zero at nonzero momentum, indicating dynamical slowing of plasma fluctuations and crystallization of the valence electrons into an exciton condensate. Our study provides compelling evidence for exciton condensation in a three-dimensional solid and establishes M-EELS as a versatile technique sensitive to valence band excitations in quantum materials.

Original languageEnglish (US)
Pages (from-to)1314-1317
Number of pages4
JournalScience
Volume358
Issue number6368
DOIs
StatePublished - Dec 8 2017

ASJC Scopus subject areas

  • General

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    Kogar, A., Rak, M. S., Vig, S., Husain, A. A., Flicker, F., Joe, Y. I., Venema, L., MacDougall, G. J., Chiang, T. C., Fradkin, E., Van Wezel, J., & Abbamonte, P. (2017). Signatures of exciton condensation in a transition metal dichalcogenide. Science, 358(6368), 1314-1317. https://doi.org/10.1126/science.aam6432