Nature 505, 657–660 (2014)

Credit: © 2014 NPG

Since the publication of Dirac's classical paper in 1931, the search for a new fundamental particle, the magnetic monopole, with non-zero magnetic monopole charge, has grasped the attention of many. The existence of magnetic monopoles is now not only supported by the work of Dirac, but by both the grand unified theory and string theory. However, both theories realize that magnetic monopoles might be too few and too massive to be detected or created in a lab, so physicists started to explore approaches to obtain such particles using condensed-matter systems. Now, Ray and co-workers report the latest observation of a Dirac monopole quasiparticle (pictured), this time in a spinor Bose–Einstein condensate. This magnetic monopole quasiparticle is in fact not a magnetic monopole fundamental particle, but a quasiparticle equivalent, and is a source of a 'synthetic magnetic field' that violates the zero-divergence law. Even though this system only resembles a true magnetic monopole, this is the first time such a quasiparticle has been detected within a system governed by quantum field theory, the framework behind subatomic particle physics.