Creation of a Dirac monopole-antimonopole pair in a spin-1 Bose-Einstein condensate

TL;DR

This paper demonstrates theoretically how to create and analyze Dirac monopole-antimonopole pairs in a spin-1 Bose-Einstein condensate using external magnetic fields, revealing complex vortex structures and their evolution.

Contribution

It introduces a method to create Dirac monopole pairs in a spinor BEC and explores their dynamics with different initial vortex configurations, providing new insights into topological defects.

Findings

Monopole-antimonopole pairs can be created with opposite synthetic charges.

Vortex structures evolve into complex configurations like vortex rings and kinks.

The initial vortex winding number affects the resulting monopole-vortex system.

Abstract

We theoretically demonstrate that a pair of Dirac monopoles with opposite synthetic charges can be created within a single spin-1 Bose-Einstein condensate by steering the spin degrees of freedom by external magnetic fields. Although the net synthetic magnetic charge of this configuration vanishes, both the monopole and the antimonopole are accompanied by vortex filaments carrying opposite angular momenta. Such a Dirac dipole can be realized experimentally by imprinting a spin texture with a nonlinear magnetic field generated by a pair of coils in a modified Helmholtz configuration. We also investigate the case where the initial state for the dipole-creation procedure is pierced by a quantized vortex line with a winding number k. It is shown that if k = -1, the resulting monopole and antimonopole lie along the core of a singly quantized vortex whose sign is reversed at the locations of the monopoles. For k = -2, the monopole and antimonopole are connected by a vortex line segment carrying two quanta of angular momentum, and hence the dipole as a whole is an isolated configuration. In addition, we simulate the long-time evolution of the dipoles in the magnetic field used to create them. For k = 0, each of the semi-infinite doubly quantized vortices splits into two singly quantized vortices, as in the case of a single Dirac monopole. For k = -1 and k = -2, the initial vortices deform into a vortex with a kink and a vortex ring, respectively.