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arXiv · 1309.7279

Exciton condensation due to electron-phonon interaction

N. V. Phan·K. W. Becker·H. Fehske
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Abstract

We show that the coupling to vibrational degrees of freedom can drive a semimetal excitonic-insulator quantum phase transition in an one-dimensional two-band f-c electron system at zero temperature. The insulating state typifies an excitonic condensate accompanied by a finite lattice distortion. Using the projector-based renormalization method we analyze the ground-state and spectral properties of the interacting electron-phonon model at half-filling. In particular we calculate the momentum dependence of the excitonic order parameter function and determine the finite critical interaction strength for the metal-insulator transition to appear. The electron spectral function reveals the strong hybridization of f- and c-electron states and the opening of a single-particle excitation gap. The phonon spectral function indicates that the phonon mode involved in the transition softens (hardens) in the adiabatic (non-adiabatic and extreme anti-adiabatic) phonon frequency regime.

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N. V. Phan, K. W. Becker, H. Fehske. 2013-09-27. Exciton condensation due to electron-phonon interaction. https://doi.org/10.1103/physrevb.88.205123

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