Partenaires

CNRS
UPS



Rechercher

Sur ce site

Sur le Web du CNRS


Accueil du site > Séminaires > Séminaires 2010 > Possible featureless spin liquid states in high magnetic field — magnetization plateaus revisited

mardi 22 Juin — 14:00

Possible featureless spin liquid states in high magnetic field — magnetization plateaus revisited

Keisuke Totsuka (Yukawa Institute for Theoretical Physics, Kyoto, Japon)

par Pierre Pujol - 22 juin 2010

Contrary to a text-book picture of magnetization processes, many examples are known both in theory and in experiment to exhibit step-like structures (magnetization plateaus), which are known to be "quantized" at rational values of magnetization. The appearance of these plateaus is a direct consequence of the formation of spin-gapped states and simple arguments tell us that normally these spin-gap states are either trivial (i.e. band-insulator-like) or accompanied by magnetic superstructures.

We re-examine this issue from an effective-field-theory viewpoint. By using semiclassical approach, we derive an effective hamiltonian for generic (antiferromagnetic) spin systems in high magnetic fields. The resulting model contains all-important Berry-phase term, whose topological interference determines whether plateaus are allowed at a given value of magnetization. On the other hand, this interference effects may cause multiple-vortex condensation and thereby leads to genuine featureless spin-liquid plateau states with topological orders.