Bosonization approach to charge and spin dynamics of 1D fermions with band-curvature

TL;DR

This paper uses bosonization to analyze charge and spin dynamics in 1D fermions with band-curvature, revealing how interactions and non-linear spectra influence excitation spectra and spectral weight transfer.

Contribution

It extends bosonization techniques to include band-curvature effects, showing how they modify the excitation spectrum and induce spin-charge coupling in 1D fermionic systems.

Findings

Bosonization captures the 2-parametric excitation spectrum due to band-curvature.

Spin-charge coupling causes asymmetric effects on charge and spin dynamical structure factors.

Charge DSF exhibits a two-peak structure; magnetic DSF shows spectral weight transfer to higher frequencies.

Abstract

We consider one-dimensional (1D) spin-1/2 fermions in a clean quantum wire, with forward scattering interactions and a non-linear single-particle spectrum, $\xi_k = v|k| + k^2/2m$ where $v$ is the Fermi velocity and $1/m$ is the band-curvature. We calculate the dynamical structure factor (DSF) of the model at small wave-vector $q$ with the help of the bosonization technique. For spinless fermions, we show that, starting from the single-parametric spectrum: $\om = u |q|$, bosonization emulates the 2-parametric excitation spectrum: $\om = u |q| \pm q^2/2m^*$, where $m^*$ decreases with increasing repulsive interactions. Moreover, away from the excitation-cone, {\it i.e.} $\om \gg u |q|$, bosonization yields the 2-pair excitation continuum of the DSF. For spinful fermions, we show that the spin-charge coupling (SCC) due to band-curvature affects charge and spin DSF in an asymmetric way. For the charge DSF, SCC manifests as a two-peak structure: a charge peak at $\om = u_\rho |q|$ but also a spin peak at $\om = u_\sigma |q|$, as charge fluctuations may decay via chargeless spin-singlet excitations. For the magnetic DSF, SCC manifests as a continuous transfer of magnetic spectral weight to frequencies $\om > u_\sigma |q|$, as spin fluctuations decay via pairs of chargeless spin and spinless charge-neutral excitations.