Non-thermal melting of Neel order in the Hubbard model

TL;DR

This paper investigates how antiferromagnetic order in the Hubbard model melts after a quench, revealing different pathways at weak and strong interactions, with implications for cold atom experiments.

Contribution

It provides a detailed analysis of non-thermal melting of Neel order in the Hubbard model using nonequilibrium dynamical mean-field theory, highlighting distinct mechanisms at different interaction strengths.

Findings

Fast energy transfer causes melting in the Mott regime.

Local moments and exchange coupling persist during melting.

Oscillations in momentum distribution relate to prethermalization.

Abstract

We study the unitary time evolution of antiferromagnetic order in the Hubbard model after a quench starting from the perfect N\'eel state. In this setup, which is well suited for experiments with cold atoms, one can distinguish fundamentally different pathways for melting of long-range order at weak and strong interaction. In the Mott insulating regime, melting of long-range order occurs due to the ultra-fast transfer of energy from charge excitations to the spin background, while local magnetic moments and their exchange coupling persist during the process. The latter can be demonstrated by a local spin-precession experiment. At weak interaction, local moments decay along with the long-range order. The dynamics is governed by residual quasiparticles, which are reflected in oscillations of the off-diagonal components of the momentum distribution. Such oscillations provide an alternative route to study the prethermalization phenomenon and its influence on the dynamics away from the integrable (noninteracting) limit. The Hubbard model is solved within nonequilibrium dynamical mean-field theory, using the density matrix-renormalization group as an impurity solver.