Spontaneous Magnetic Ordering in a Ferromagnetic Spinor Dipolar Bose-Einstein Condensate

TL;DR

This paper investigates the complex spin dynamics and emergent magnetic structures in a ferromagnetic spinor Bose-Einstein condensate influenced by dipolar interactions, revealing partial agreement with experimental observations and discussing potential reasons for discrepancies.

Contribution

It introduces a detailed theoretical analysis of spin dynamics in a dipolar Bose-Einstein condensate, highlighting the formation of magnetic structures and addressing differences with experimental results.

Findings

Emergence of checkerboard and stripe magnetic patterns during dynamics

Discrepancy in periodicity of magnetic order compared to experiments

Checkerboard pattern dissolves in simulations over time

Abstract

We study the spin dynamics in a spin-1 ferromagnetic Bose-Einstein condensate with magnetic dipole-dipole interaction (MDDI) based on the Gross-Pitaevskii and Bogoliubov theories. We find that various magnetic structures such as checkerboards and stripes emerge in the course of the dynamics due to the combined effects of spin-exchange interaction, MDDI, quadratic Zeeman and finite-size effects, and non-stationary initial conditions. However, the short-range magnetic order observed by the Berkeley group [Phys. Rev. Lett. {\bf 100}, 170403 (2008)] is not fully reproduced in our calculations; the periodicity of the order differs by a factor of three and the checkerboard pattern eventually dissolves in our numerical simulations. Possible reasons for the discrepancy are discussed.