Far-from-equilibrium spin transport in Heisenberg quantum magnets

TL;DR

This study investigates far-from-equilibrium spin dynamics in ultracold atom-based Heisenberg quantum magnets, revealing diffusion in 1D and super-diffusion in 2D, with detailed experimental measurements of spin correlation decay.

Contribution

It provides the first experimental observation of wave vector-dependent spin decay and distinguishes diffusion and super-diffusion in 1D and 2D quantum magnets.

Findings

Diffusion coefficient in 1D is approximately 0.22.

Spin decay rate depends strongly on wave vector.

2D systems exhibit anomalous super-diffusive behavior.

Abstract

We study experimentally the far-from-equilibrium dynamics in ferromagnetic Heisenberg quantum magnets realized with ultracold atoms in an optical lattice. After controlled imprinting of a spin spiral pattern with adjustable wave vector, we measure the decay of the initial spin correlations through single-site resolved detection. On the experimentally accessible timescale of several exchange times we find a profound dependence of the decay rate on the wave vector. In one-dimensional systems we observe diffusion-like spin transport with a dimensionless diffusion coefficient of 0.22(1). We show how this behavior emerges from the microscopic properties of the closed quantum system. In contrast to the one-dimensional case, our transport measurements for two-dimensional Heisenberg systems indicate anomalous super-diffusion.