Coherent order parameter oscillations in the ground state of the excitonic insulator Ta₂NiSe₅.

ABSTRACT: The excitonic insulator is an intriguing electronic phase of condensed excitons. A prominent candidate is the small bandgap semiconductor Ta₂NiSe₅, in which excitons are believed to undergo a Bose-Einstein condensation-like transition. However, direct experimental evidence for the existence of a coherent condensate in this material is still missing. A direct fingerprint of such a state would be the observation of its collective modes, which are equivalent to the Higgs and Goldstone modes in superconductors. We report evidence for the existence of a coherent amplitude response in the excitonic insulator phase of Ta₂NiSe₅. Using nonlinear excitations with short laser pulses, we identify a phonon-coupled state of the condensate that can be understoo

SUBMITTER: Werdehausen D 

PROVIDER: S-EPMC5938280 | biostudies-literature | 2018 Mar

REPOSITORIES: biostudies-literature