Scientists from Helmholtz-Zentrum Berlin (HZB) used neutron scattering on magnetic crystals of calcium cuprate to show that electrons in spin-chains - two chains of copper oxide chemically bonded together – split into spins and charges on the chains.  The spinons, or chains, then pair up again due to the ladder effect.

Professor Alan Tennant, head of the Institute of Complex Magnetic Materials at HZB said: “The geometry of the ladders in fact plays a special role: the spinons always appear in pairs and when they move apart, they force a reorganisation of the intervening electrons that cost energy.  The energy grows with separation – like a rubber band.”

Professor Bella Lake, Head of Junior Research Group at HZB likens the pair of the spinions to those of quarks binding to form hadrons and mesons.  “The spinons have different properties to those of the original electrons.  In fact, they are analogous to quarks,” she said.  “We have found that excitation of individual chains are confined in a similar way to that in which elementary quarks are held together.

In the 1990s Professor Alexi Tsvelik from Brookhaven National Laboratory (USA) predicted the confinement process in spin-ladders found in condensed matter physics.  He said the formation of hadrons is well established on a qualitative level, but its quantitative aspects remain unresolved.  Its unknown how to relate the theoretical parameters to the observed hadron masses.  “This is one of the reasons why condensed matter analogues are interesting.  They provide examples of confinement for which detailed descriptions have been achieved.”

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.  Quarks are held together by a strong force, that grows stronger with increasing distance and combine to form protons and neutrons.