Evidence of Bose-Einstein condensation in a quantum magnet formed by free radical tetramers
ORAL
Abstract
Several experimental realizations of quantum magnets showing Bose-Einstein condensates (BEC) have been reported in the literature. The typical scenario invokes a ground state described by pairs of localized spins forming singlets. An external magnetic field acts as an effective chemical potential for triplet excitations that can subsequently form the BEC. The T versus H phase diagrams typically display a ``dome'' structure bounded by two critical fields and a field-dependent critical temperature.
In this work, we present experimental and theoretical evidence of Bose-Einstein condensation in an organic crystal formed of weakly interacting S=1/2 tetramers. We show that the physics can be described in terms of a fully rotational invariant system of quantum spins without frustration. Two BEC phases exist: at low fields, only the edge spins of each tetramer contribute to the condensate, while at high-fields, the order is determined by the two central spins. These unusual BECs are separated by a quantum state with half of the spins forming dimerized pairs, and the other half aligned in the direction of the field.
In this work, we present experimental and theoretical evidence of Bose-Einstein condensation in an organic crystal formed of weakly interacting S=1/2 tetramers. We show that the physics can be described in terms of a fully rotational invariant system of quantum spins without frustration. Two BEC phases exist: at low fields, only the edge spins of each tetramer contribute to the condensate, while at high-fields, the order is determined by the two central spins. These unusual BECs are separated by a quantum state with half of the spins forming dimerized pairs, and the other half aligned in the direction of the field.
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Presenters
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Andres Saul
- CINaM-CNRS UMR 7325 Campus de Luminy, Aix-Marseille University
- Aix-Marseille University
- CINaM/CNRS, Aix-Marseille University
- CINaM/CNRS, Aix-Marseille Univ.