The dynamical magnetic correlations in \tbti\, have been investigated using polarized inelastic neutron scattering. Dispersive excitations are observed, emerging from pinch points in reciprocal space and characterized by an anisotropic spectral weight. Anomalies in the crystal field and phonon excitation spectrum at Brillouin zone centers are also reported. These findings suggest that Coulomb phases, although they present a disordered ground state with dipolar correlations, allow the propagation of collective excitations. They also point out a strong spin-lattice coupling, which likely drives effective interactions between the 4f quadrupolar moments.
@article{arxiv.1305.6363,
title = {Anisotropic propagative excitations and quadrupolar effects in Tb$_2$Ti$_2$O$_7$},
author = {Solène Guitteny and Julien Robert and Pierre Bonville and Jacques Ollivier and Claudia Decorse and Paul Steffens and Martin Boehm and Hannu Mutka and Isabelle Mirebeau and Sylvain Petit},
journal= {arXiv preprint arXiv:1305.6363},
year = {2013}
}