Transverse spin dynamics in the anisotropic Heisenberg model realized with ultracold atoms

TL;DR

This study uses ultracold atoms to simulate 1D anisotropic Heisenberg spin chains, revealing rapid local spin decay and multiple dephasing mechanisms, including a novel hole-magnon coupling, enhancing understanding of Hubbard model dynamics.

Contribution

First experimental observation of diverse dephasing mechanisms in ultracold atom simulations of anisotropic Heisenberg models, including a new hole-magnon coupling effect.

Findings

Fast local spin decay controlled by anisotropy

Observation of inhomogeneous decay due to effective magnetic field variations

Identification of a new hole-magnon coupling mechanism

Abstract

In Heisenberg models with exchange anisotropy, transverse spin components are not conserved and can decay not only by transport, but also by dephasing. Here we utilize ultracold atoms to simulate the dynamics of 1D Heisenberg spin chains, and observe fast, local spin decay controlled by the anisotropy. Additionally, we directly observe an effective magnetic field created by superexchange which causes an inhomogeneous decay mechanism due to variations of lattice depth between chains, as well as dephasing within each chain due to the twofold reduction of the effective magnetic field at the edges of the chains and due to fluctuations of the effective magnetic field in the presence of mobile holes. The latter is a new coupling mechanism between holes and magnons. All these dephasing mechanisms, corroborated by extensive numerical simulations, have not been observed before with ultracold atoms and illustrate basic properties of the underlying Hubbard model.