Inelastic neutron scattering studies of the Jahn-Teller phase transition in TbVO4

TbVO 4 undergoes a crystallographic phase transition at 33K caused by the Jahn-Teller coupling between the Tb 3+ ions and the lattice. Using inelastic neutron scattering experiments it is found that the phase transition is characterized by the divergence in the intensity of a central peak (at omega =0) in the neutron scattering at zero wavevector. The anticrossing of an acoustic phonon mode and an electronic excitation at about 0.48 THz is also observed, the coupling between which increases as the temperature is lowered towards the transition.