ScienceDaily (Nov. 30, 2009) — The concept of confinement is one of the central ideas in modern physics. The most famous example is that of quarks which bind together to form protons and neutrons. Now Prof. Bella Lake from Helmholtz-Zentrum Berlin together with an international team of scientists report for the first time an experimental realization and a proof of confinement phenomenon observed in a condensed matter system.

Alexei Tsevelik. (Credit: Brookhaven National Laboratory)

The concept of confinement states that in certain systems the constituent particles are bound together by an interaction whose strength increases with increasing particle separation. In the case of quarks they are held together by the so called strong force, a force that grows stronger with increasing distance. As a consequence individual particles like quarks don't exist in a free state and their properties can be observed only indirectly. In the 1990s Prof Alexei Tsvelik from Brookhaven National Laboratory (USA) and co-workers predicted an analogous confinement process in systems known as spin-ladders found in condensed matter physics. Experimental confirmation of this phenomenon has however only been achieved recently as described by Bella Lake et al in the current issue of the journal Nature Physics.

The most famous example of confinement is of quarks which are held together in protons and neutrons, for example, 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," Alexei M.Tsvelik of the Department of Condensed Matter Physics and Materials Science, Brookhaven National Laboratory, 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."

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