Magnetic Spinion Confinement Confirmed

An experiment at the UK’s Rutherford Appleton Laboratory has confirmed that spinons, which are particle-like magnetic excitations, can be confined in a magnetic insulator similarly to how quarks are confined within individual protons and neutrons. The finding, could offer new avenues of study in Quantum Chromodynamics, a theory that describes fundamental interactions of quarks.

The spinon confinement observations were made by an international team of physicists, who describe the theory and their new observations in the November 29th issue of Nature Physics.

"The concept of confinement is one of the central ideas in modern physics, being at the core of the theory of nuclear forces," said theoretical physicist Alexei Tsevelik. "In certain systems, when constituent particles are bound together by an interaction whose strength increases with increasing particle separation, individual particles cannot exist in a free state and therefore can be observed only indirectly." One example of confinement is of quarks which are held together in protons and neutrons by the strong force, a force that grows stronger with increasing distance.

"It has been interesting for us that a similar situation of confinement can be modeled in condensed matter systems," Tsvelik said. "Instead of quarks being confined in protons and neutrons, we have other quantum entities that act just like particles -- elementary excitations of magnetic systems called spinons."

In the case of the current experiment, the spinons exist on parallel chains of copper-oxide separated by inert calcium. Spinons on individual chains are not confined, but as soon as two chains are brought together to form ladder-like arrangements, the inter-ladder interactions confine the spinons.

"That is, the spinons can appear now only in pairs and cannot fly away from each other too far," Tsvelik said. "The result of this confinement is a particle we call a magnon. It is like two quarks pairing up to form a meson. Now that we have an example of confinement in a condensed matter system, our next step is to check further predictions of the theory to make sure there are no unpleasant surprises," Tsvelik said.