Particle-like Solitons at Absolute Zero

According to quantum physicists from the ARC Centre of Excellence for Quantum-Atom Optics, Australian National University and the University of Hertfordshire, UK, Nature at its most fundamental consists of quantum fields. These can arrange themselves in particle-like three-dimensional structures called topological solitons. One such structure is called a "Skyrmion", after the British physicist Tony Skyrme, who suggested that protons and neutrons might be Skyrmions of the nuclear force field.

A theoretical study just published in Physical Review Letters ["Energetically stable particle-like Skyrmions in a trapped Bose-Einstein condensate", C.M. Savage and J. Ruostekoski, Phys. Rev. Lett. 91, 010403 (2003)] shows that Skyrmions are stable in dilute gas Bose-Einstein condensates. These are quantum gases whose temperature approaches absolute zero. This may stimulate experimental study of the otherwise inaccessible physics of topological solitons in quantum fields.

This cut-away image shows the Skyrmion's three dimensional structure. It consists of two separate matter wave fields, which are actually different atomic states of the same atom. One of the fields is represented by the central blue surface. It has a hole down its center because it is spinning, creating a vortex, just like water spiraling down a plug hole. The other field is represented by surfaces sliced in half, with colors showing its density on the sliced face. Note the high density line threading through the vortex hole. The second field has a vortex wrapped around into a ring, surrounding the first vortex in a plane perpendicular to it. The structure is thus a ring vortex in one field surrounding a line vortex in then other. Such a structure is also know as a "vorton". The line vortex stabilises the ring vortex from its usual fate of shrinking to a point.

Download paper: PRL     cond-mat/0306112