paper

Nature of ground states in one-dimensional electron-phonon Hubbard models at half-filling

arXiv:1502.01981 · doi:10.1103/PhysRevB.91.085114

Abstract

The renormalization group technique is applied to one-dimensional electron-phonon Hubbard models at half-filling and zero temperature. For the Holstein-Hubbard model, the results of one-loop calculations are congruent with the phase diagram obtained by quantum Monte Carlo simulations in the plane for the phonon-mediated interaction and the Coulomb interaction . The incursion of an intermediate phase between a fully gapped charge-density-wave state and a Mott antiferromagnet is supported along with the growth of its size with the molecular phonon frequency . We find additional phases enfolding the base boundary of the intermediate phase. A Luttinger liquid line is found below some critical , followed at larger by a narrow region of bond-order-wave ordering which is either charge or spin gapped depending on . For the Peierls-Hubbard model, the region of the plane with a fully gapped Peierls-bond-order-wave state shows a growing domination over the Mott gapped antiferromagnet as the Debye frequency decreases. A power law dependence is found to map out the boundary between the two phases, whose exponent is in good agreement with the existing quantum Monte Carlo simulations performed when a finite nearest-neighbor repulsion term is added to the Hubbard interaction.

11 pages, 10 figures

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