Fate of the excitonic insulator in the presence of phonons

Article

关键词: LONG-RANGE ORDER;    CONDENSATION;    PHASE;    TRANSITIONS;    METAL;    TISE2;   

DOI  :  10.1103/PhysRevB.90.195118

来源: SCIE

【 摘 要 】

The influence of phonons on the formation of the excitonic insulator has hardly been analyzed so far. Recent experiments on Ta2NiSe5, 1T -TiSe2, andTmSe(0.45)Te(0.55), being candidates for realizing the excitonic-insulator state, suggest, however, that the underlying lattice plays a significant role. Employing the Kadanoff-Baym approach we address this issue theoretically. We show that owing to the electron-phonon coupling a static lattice distortion may arise at the excitonic instability. Most importantly such a distortion will destroy the acoustic phase mode being present if the electron-hole pairing and condensation is exclusively driven by the Coulomb interaction. The absence of off-diagonal long-range order, when lattice degrees of freedom are involved, challenges that excitons in these materials form a superfluid condensate of Bose particles or Cooper pairs composed of electrons and holes.

【 授权许可】

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