Bosonization of dimerized spinless-fermion and Hubbard chains

TL;DR

This paper advances the bosonization method for one-dimensional fermionic models by properly incorporating Klein factors and applying a variational approach to nonlinear terms, with applications to dimerized and Hubbard chains, and effects of 3D coupling.

Contribution

It introduces an extended self-consistent harmonic approximation that accurately accounts for Klein factors in bosonized Hamiltonians of dimerized and Hubbard chains.

Findings

Klein factors are crucial for correct bosonization of these models.

The method captures the effects of dimerization and periodic modulation.

Charge excitations are coupled to 3D environments, spin excitations are unaffected.

Abstract

The low energy properties of different one-dimensional fermionic lattice models are investigated using the bosonization technique. We attach much importance to a proper consideration of the Klein factors which are neglected or inaccurately treated in the majority of the literature. In order to deal with the nonlinear terms, arising from the dimerization or similar scattering processes, we use the self-consistent harmonic approximation (SCHA), a variational method where the nonlinearities are replaced by a quadratic potential. We construct an extension of the SCHA in order to account for the existence of Klein factors in bosonized Hamiltonians. As prototypical models we consider one-dimensional dimerized spinless fermions and Hubbard models with periodic modulation of the hopping and of the chemical potential, respectively. In an attempt to describe more realistic systems we also consider a model where one-dimensional electrons are coupled to a three-dimensional conduction band via a local interaction. In order to see how the one-dimensional electron system is modified in the presence of the three-dimensional environment, we calculate the charge and the spin susceptibility, and analyze the collective excitations within RPA. We find that the spin excitations remain unaffected while in the charge channel, the collective modes of the one-dimensional and three-dimensional subsystems are coupled.