Towards a model of a dynamical Jahn-Teller coupling at very low temperatures in Tb2Ti2O7

We present an interpretation of zero-field energy integrated (diffuse) neutron scattering and of high-field magnetization data at very low temperature in the frustrated pyrochlore system Tb2Ti2O7. This material has antiferromagnetic exchange interactions, and it is expected to have an Ising character at low temperature. Contrary to expectations, it shows no magnetic ordering down to 0.05 K, being thus labeled a spin liquid. However, the ground state in Tb2Ti2O7 is not a mere fluctuating moment paramagnet but, as demonstrated by very recent experiments, a state where the electronic degrees of freedom are hybridized with the phononic variables in an unconventional way. We show here that, by approximating this complex and still unraveled electron-phonon interaction by a dynamic Jahn-Teller coupling, one can account rather well for the diffuse neutron scattering and the low-temperature isothermal magnetization.