Spectral function of spinless fermions on a one-dimensional lattice

TL;DR

This paper analyzes the spectral function of interacting spinless fermions on a one-dimensional lattice using Bethe ansatz, revealing singularities, bound states, and validating results with tDMRG simulations, with implications for dynamical structure factors.

Contribution

It provides exact singularity exponents for the spectral function of 1D fermions away from half-filling using Bethe ansatz and compares these with numerical tDMRG results.

Findings

Identification of power-law singularities near single-particle energies

Discovery of a second divergence related to two-particle bound states

Validation of tDMRG accuracy in capturing Green's function decay

Abstract

We study the spectral function of interacting one-dimensional fermions for an integrable lattice model away from half-filling. The divergent power-law singularity of the spectral function near the single-particle or single-hole energy is described by an effective x-ray edge type model. At low densities and for momentum near the zone boundary, we find a second divergent singularity at higher energies which is associated with a two-particle bound state. We use the Bethe ansatz solution of the model to calculate the exact singularity exponents for any momentum and for arbitrary values of chemical potential and interaction strength in the critical regime. We relate the singularities of the spectral function to the long-time decay of the fermion Green's function and compare our predictions with numerical results from the time-dependent density matrix renormalization group (tDMRG). Our results show that the tDMRG method is able to provide accurate time decay exponents in the cases of power-law decay of the Green's function. Some implications for the line shape of the dynamical structure factor away from half-filling are also discussed. In addition, the spectral weight of the Luttinger liquid result for the dynamical structure factor of the Heisenberg model at zero field is compared with the exact two-spinon contribution.