Anisotropic propagating excitations and quadrupolar effects in Tb2Ti2O7

Phys Rev Lett. 2013 Aug 23;111(8):087201. doi: 10.1103/PhysRevLett.111.087201. Epub 2013 Aug 20.

Abstract

The dynamical magnetic correlations in Tb2Ti2O7 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.