Half-solitons in a polariton quantum fluid behave like magnetic monopoles

TL;DR

This paper demonstrates that half-solitons in a polariton quantum fluid act like magnetic monopoles, showing behavior analogous to magnetic charges and opening avenues for magnetic current generation in quantum fluids.

Contribution

It provides the first experimental evidence of half-solitons behaving as magnetic monopoles in a polariton condensate.

Findings

Half-solitons behave as magnetic monopoles.

Half-solitons are accelerated by an effective magnetic field.

Spatial separation of opposite charges observed.

Abstract

Monopoles are magnetic charges, point-like sources of magnetic field. Contrary to electric charges they are absent in Maxwell's equations and have never been observed as fundamental particles. Quantum fluids such as spinor Bose-Einstein condensates have been predicted to show monopoles in the form of excitations combining phase and spin topologies. Thanks to its unique spin structure and the direct optical control of the fluid wavefunction, an ideal system to experimentally explore this phenomenon is a condensate of exciton-polaritons in a semiconductor microcavity. We use this system to create half-solitons, non-linear excitations with mixed spin-phase geometry. By tracking their trajectory, we demonstrate that half-solitons behave as monopoles, magnetic charges accelerated along an effective magnetic field present in the microcavity. The field-induced spatial separation of half-solitons of opposite charges opens the way to the generation of magnetic currents in a quantum fluid.