Phase Transitions in Frustrated Systems

The success in understanding the collective behavior of conventional magnetic materials has led to an increased interest in systems that exhibit a novel type of ordering as a consequence of competing interactions or "frustration". In particular, geometrically frustrated systems (having as a basic building block triangles of antiferromagnetic bonds) have been and are still the object of extensive experimental and theoretical studies.

 The phenomenon of frustration is ubiquitous in condensed matter physics. It arises in magnetic systems when there is no unique direction for a spin to choose to minimize its energy, leading to non trivial and often multiple ground states. It can also be found in molecular crystals, superconducting Josephson junction arrays and glassy materials. As a consequence of frustration, spectacular and often unexpected behaviour is encountered at low temperatures due to the high degeneracy of the ground state.

The nature of excitations in these systems is an interesting problem. In some cases, topological excitations can lead to rather novel phase transitions, such as a defect unbinding transition of vortices.The modelling of these systems requires intensive computational effort using parallel machines such as the High Performance Computing Facility recently installed at the University of Manitoba. The results of this study should enhance our understanding of these frustrated antiferromagnets in order to compare with available experimental results.