Charge-density wave induced by combined electron-electron and electron-phonon interactions in 1$T$-TiSe${}_2$: A variational Monte Carlo study

Abstract

To clarify the origin of a charge-density wave (CDW) phase in 1$T$-TiSe${}_2$, we study the ground state property of a half-filled two-band Hubbard model in a triangular lattice including electron-phonon interaction. By using the variational Monte Carlo method, the electronic and lattice degrees of freedom are both treated quantum mechanically on an equal footing beyond the mean-field approximation. We find that the cooperation between Coulomb interaction and electron-phonon interaction is essential to induce the CDW phase. We show that the "pure" exciton condensation without lattice distortion is difficult to realize under the poor nesting condition of the underlying Fermi surface. Furthermore, by systematically calculating the momentum resolved hybridization between the two bands, we examine the character of electron-hole pairing from the viewpoint of BCS-BEC crossover within the CDW phase and find that the strong-coupling BEC-like pairing dominates. We therefore propose that the CDW phase observed in 1$T$-TiSe${}_2$ originates from a BEC-like electron-hole pairing.

7 pages, 4 figures

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Cited by in corpus (8)

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• Photoinduced electron-electron pairing in the extended Falicov-Kimball model
• Formation and condensation of excitonic bound states in the generalized Falicov-Kimball model
• Unified description of cuprate superconductors using four-band $d$-$p$ model
• Excitonic Insulator State of the Extended Falicov-Kimball Model in the Cluster Dynamical Impurity Approximation
• Carrier-Density Control of the Quantum-Confined 1$T$-TiSe${}_2$ Charge-Density-Wave
• DMRG study of exciton condensation in the extended Falicov-Kimball model