Spin dynamics in a one-dimensional ferromagnetic Bose gas

TL;DR

This paper studies spin excitation propagation in a 1D ferromagnetic Bose gas, revealing unique crossover behavior in spin correlations that challenge existing low-energy universality classes.

Contribution

It derives the asymptotic behavior of spin-spin correlations in a strongly interacting 1D ferromagnetic Bose gas, uncovering novel crossover phenomena.

Findings

Spin waves exhibit sound-like dispersion, transverse excitations are quadratic.

The correlation function shows a crossover from trapped to open spin wave regimes.

Results reveal a new universality class not seen in known 1D quantum systems.

Abstract

We investigate the propagation of spin excitations in a one-dimensional (1D) ferromagnetic Bose gas. While the spectrum of longitudinal spin waves in this system is sound-like, the dispersion of transverse spin excitations is quadratic making a direct application of the Luttinger Liquid (LL) theory impossible. By using a combination of different analytic methods we derive the large time asymptotic behavior of the spin-spin dynamical correlation function for strong interparticle repulsion. The result has an unusual structure associated with a crossover from the regime of trapped spin wave to an open regime and does not have analogues in known low-energy universality classes of quantum 1D systems.