Physicists from the Faculty of Physics at the University of Warsaw, in collaboration with scientists from the University of British Columbia, have made a groundbreaking discovery in the field of quantum physics. The research team described the mechanism of formation of so-called “lone spinons” – exotic quantum excitations that are single, unpaired spins/ that consist of single, unpaired spins . The results of these advanced theoretical analyses were published in the prestigious journal Physical Review Letters. 

Although magnetism has been known to humanity for millennia, its fundamental nature has long remained a mystery. Only with the development of quantum mechanics in the 20th century was it revealed that magnetic phenomena are caused by interactions between spins — fundamental properties of particles, alongside mass and charge. As early as the 1930s, Hans Bethe proposed a mathematical model describing such systems: the one-dimensional Heisenberg model. In 1981, Faddeev and Takhtajan predicted the existence of “spinons” — excitations that carry a spin of 1/2, but always occur in pairs. 

The latest research by the Polish-Canadian team, however, shows that spinons can also appear independently. All that is required is the addition of a single spin to the system or the use of an ordered model called a valence-bond solid (VBS), in which spins pair up. In such a model, a lone spinon can move through the network of paired spins, like a lone electron in an ordered structure. 

Importantly, this theoretical prediction has been confirmed by recent experimental research published in Nature Materials. This means that “lone” spinons are no longer just a mathematical construct, but a real physical phenomenon that can be observed. 

The project was carried out with the support of the National Science Centre, the University of Warsaw’s Excellence Initiative, and Canadian and American partners, including the Canada First Research Excellence Fund and the Kavli Institute for Theoretical Physics.