Anomalous dynamical effects in calcite CaCO3

We present the results of an inelastic neutron scattering study of calcite. A continuum of excitations is observed, coupled with a soft phonon mode. Similar excitation spectra have been found in a number of other materials, due to electronic effects. However, calcite is an insulator, and we suggest that our results can instead be explained by a rather unexpected solution of the conventional picture that arises from coupling between phonon and relaxation modes.