Energy shift of magnons in a ferromagnetic spinor-dipolar Bose-Einstein condensate

TL;DR

This paper investigates how magnetic dipole-dipole interactions affect magnon effective mass and dynamics in a spinor Bose-Einstein condensate, aligning with recent experimental observations.

Contribution

It demonstrates that dipolar interactions modify magnon effective mass and dynamics, providing a theoretical explanation for experimental results.

Findings

Magnon effective mass increases due to dipolar interactions.

Changing magnetic field direction alters magnon mass.

Magnon acceleration correlates with mass changes.

Abstract

Motivated by the recent experiment performed by the Berkeley group [G. E. Marti {\it et al.}, Phys. Rev. Lett. {\bf 113}, 155302 (2014)], we consider the dynamics of magnons in a spin-1 spinor-dipolar Bose-Einstein condensate, using mean-field theory. We show that the effective mass of a magnon is increased by the magnetic dipole-dipole interaction, as observed in the experiment. The magnon mass is also decreased by changing the direction of the magnetic field. The increase and decrease in the magnon mass manifest themselves in the acceleration of the magnons.