Berlin 2005 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 21: Symposium Frustrated Systems

TT 21.6: Hauptvortrag

Montag, 7. März 2005, 16:20–16:45, TU H104

Geometrical Frustration as Paradigm for Low Temperature Physics — •Arthur Ramirez — Bell Laboratories, Lucent Technologies, Murray Hill, USA

The study of geometrical frustration in triangle-based magnets continues to yield surprises. Phases such as spin liquid and spin ice are manifestations of low energy anharmonicity in full and as such, pose significant challenges for theory. The key ingredient for geometrical frustration, namely underconstraint from order parameter/space group incompatibility, leads to large spectral weight downshift. When these degrees of freedom continue to fluctuate, novel liquid-like magnetic states emerge. The notion of geometrical frustration is broadly applicable in magnetism and can be used to understand selected orbital ordering and heavy fermion systems. These ideas are also portable to non-magnetic systems and I’ll describe one example, the frustrated soft mode in the negative thermal expansion material, ZrW2O8. Thus a different view of low-temperature phenomena emerges, namely strong coupling at temperatures well below the mean field energy scale.