@article{aad76e3445da41b79190080b7651be50,
title = "Signatures of exciton condensation in a transition metal dichalcogenide",
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.",
author = "Anshul Kogar and Rak, {Melinda S.} and Sean Vig and Husain, {Ali A.} and Felix Flicker and Joe, {Young Il} and Luc Venema and MacDougall, {Greg J.} and Chiang, {Tai C.} and Eduardo Fradkin and {Van Wezel}, Jasper and Peter Abbamonte",
note = "Funding Information: We thank C. M. Varma, A. H. MacDonald, G. Baym, and A. J. Leggett for discussions and I. Bozovic, J. D. Stack, and S. A. Kivelson for feedback on the manuscript. This work was funded by the Gordon and Betty Moore Foundation{\textquoteright}s EPiQS Initiative through grant GBMF-4542. Development of the M-EELS instrument was supported by the U.S. Department of Energy (DOE) Center for Emergent Superconductivity, an Energy Frontier Research Center funded by the DOE Office of Science under award DE-AC02-98CH10886, with equipment provided by DOE grants DE-FG02-08ER46549 and DE-FG02-07ER46453. J.v.W. acknowledges support from a VIDI grant from the Netherlands Organization for Scientific Research (NWO). G.J.M. and E.F. acknowledge support from DOE grant DE-SC0012368. T.C.C. acknowledges support from DOE grant DE-FG02-07ER46383. F.F. acknowledges support from a Lindemann Trust Fellowship of the English Speaking Union and the Astor Junior Research Fellowship of New College, University of Oxford. The data presented in this manuscript are available from the authors upon reasonable request. Funding Information: We thank C. M. Varma, A. H. MacDonald, G. Baym, and A. J. Leggett for discussions and I. Bozovic, J. D. Stack, and S. A. Kivelson for feedback on the manuscript. This work was funded by the Gordon and Betty Moore Foundation{\textquoteright}s EPiQS Initiative through grant GBMF-4542. Development of the M-EELS instrument was supported by the U.S. Department of Energy (DOE) Center for Emergent Superconductivity, an Energy Frontier Research Center funded by the DOE Office of Science under award DE‐AC02‐98CH10886, with equipment provided by DOE grants DE-FG02-08ER46549 and DE-FG02-07ER46453. J.v.W. acknowledges support from a VIDI grant from the Netherlands Organization for Scientific Research (NWO). G.J.M. and E.F. acknowledge support from DOE grant DE-SC0012368. T.C.C. acknowledges support from DOE grant DE-FG02-07ER46383. F.F. acknowledges support from a Lindemann Trust Fellowship of the English Speaking Union and the Astor Junior Research Fellowship of New College, University of Oxford. The data presented in this manuscript are available from the authors upon reasonable request. Publisher Copyright: {\textcopyright} 2017, American Association for the Advancement of Science. All rights reserved.",
year = "2017",
month = dec,
day = "8",
doi = "10.1126/science.aam6432",
language = "English (US)",
volume = "358",
pages = "1314--1317",
journal = "Science",
issn = "0036-8075",
publisher = "American Association for the Advancement of Science",
number = "6368",
}