The V15 molecule, a multi-spin two-level system: adiabatic LZS transition with or without dissipation and Kramers theorem

Abstract

The so-called V15 molecule is formed of 15 spins 1/2 antiferromagnetically coupled. The resultant spin is equal to 1/2. Contrary to what is expected at first sight, this half-integer spin is gapped. We show that this is a consequence of the multi-spin character of the molecule. Time reversal symmetry (Kramers theorem) is preserved due to the existence of a groundstate degeneracy larger than 2. Magnetization experiments have been performed at different temperatures, sweeping-field rates and couplings with the cryostat. Their interpretation in terms of the Landau-Zener-Stuckelberg model gives evidence for adiabatic LZS spin reversal with and without dissipation.

arXiv commentto be published in the supplement of the Progress of Theoretical Physics, proceedings of the 16th Nishinomiya-Yukawa Memorial Symposium held in the city of Nishinomiya, Japan, Nov. 13-14, 2001

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