Quantum statistics of interacting dimer spin systems.
The compound TlCuCl(3) represents a model system of dimerized quantum spins with strong interdimer interactions. We investigate the triplet dispersion as a function of temperature by inelastic neutron scattering experiments on single crystals. By comparison with a number of theoretical approaches we demonstrate that the description of Troyer, Tsunetsugu, and Würtz [Phys. Rev. B 50, 13 515 (1994)10.1103/Phys. Rev. B 50, 13515] provides an appropriate quantum statistical model for dimer spin systems at finite temperatures, where many-body correlations become particularly important.
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