May 13 2010
An important model to explain high-temperature superconductivity is the so-called 'quantum spin liquid'. Scientists are therefore interested in understanding the low-energy excitations of this magnetic state. Now, a theoretical study by a research team from RIKEN and the Massachusetts Institute of Technology, USA, has explained how the properties of spin liquids could be revealed by a simple heat-transfer experiment.
In an insulating magnetic crystal, the electronic spins are localized to the atoms that form the crystal lattice. For most such magnets, or antiferromagnets, the chemical bonds favor an arrangement where, at low temperatures, each spin points in a direction opposite to that of its neighbor. However, on a triangular lattice, such as the 'Kagome lattice', a spin cannot simultaneously be opposite to all of its neighbors. The spins in these magnets never order, even at very low temperatures-giving rise to the name quantum spin liquid.
"Spin liquids have an exotic electronic state because [their] electrons can effectively dissociate into distinguishable spin- and charge-carrying particles," explains team-member Naoto Nagaosa from the RIKEN Advanced Science Institute, Wako. "The spin-carrying particle is called a spinon and determines the low-energy properties of the magnet."