TlCuCl3 has a singlet ground state with the excitation gap Δ=0.65 meV. The magnetic excitations in TlCuCl3 have been investigated by means of neutron inelastic scattering experiments. The constant-Q energy scan profiles were collected in the a∗−c∗ plane. A well-defined single magnetic excitation mode was observed. The dispersion relations along four different directions were determined. The lowest excitation occurs at Q=(h,0,l) with integer h and odd l, as observed in KCuCl3. A cluster series expansion up to the sixth order was applied to analyze the dispersion relations, and the individual exchange interactions were evaluated. It was demonstrated that TlCuCl3 is a strongly coupled spin-dimer system.
@article{arxiv.cond-mat/0108130,
title = {Magnetic Excitations of the Spin Gap System TlCuCl$_3$},
author = {A. Oosawa and T. Kato and H. Tanaka and K. Kakurai and M. Mueller and H. -J. Mikeska},
journal= {arXiv preprint arXiv:cond-mat/0108130},
year = {2007}
}