The single-particle spectral function of the extended Peierls-Hubbard model at half-filling and quarter-filling

TL;DR

This study uses exact diagonalization with twisted boundary conditions to analyze the single-particle spectral function of the extended Peierls-Hubbard model at different fillings, revealing how interactions and Peierls instability affect spin-charge separation and spectral features.

Contribution

It provides a detailed analysis of the spectral function in the extended Peierls-Hubbard model at half and quarter fillings, highlighting the effects of interactions and Peierls distortion on spin-charge separation.

Findings

Spin-charge separation persists at half-filling for small Peierls distortion.

Increasing nearest-neighbor interaction V can induce a charge-density-wave state.

At quarter-filling, the system exhibits an antiferromagnetic Mott insulator with a small gap.

Abstract

By utilizing the twisted boundary conditions in the exact diagonalization method, we investigate the single-particle spectral function of the extended Peierls-Hubbard model at both half-filling and quarter filling. In one-dimensional (1D) interacting systems, the spin-charge separation can typically be identified in the single-particle spectral function by observing the distinct spinon and holon bands. At half filling, starting from the pure 1D Hubbard model with the on-site interaction $U=10$, we observe that the band structure indicative of the spin-charge separation gradually transitions to four individual bands as the Peierls instability $\delta$ increases. At $U=10$ and $\delta=0.2$ where the spin-charge separation is still observable, increasing the nearest-neighbor interaction $V$ can drive the system to a charge-density-wave (CDW) state when $V\gtrsim U/2$, without the obeservation of spinon and holon bands. At quarter-filling, on the other hand, the ground state of Peierls-Hubbard model manifests an antiferromagnetic Mott insulator in units of dimers. Increasing $U$ results in only a very small gap in the single-particle spectrum because even for $U=+\infty$, with the model transforming into a noninteracting half-filled dimerized tight-binding model, its gap determined by the Peierls instability $\delta$ remains small. Conversely, increasing $V$ can effectively open the single-particle gap and make the spinon and holon bands more prominent.