Understanding Paramagnetic Spin Correlations in the Spin-Liquid   Pyrochlore Tb2Ti2O7
  Recent elastic and inelastic neutron scattering studies of the highly frustrated pyrochlore antiferromagnet Tb2Ti2O7 have shown some very intriguing features that cannot be modeled by the local <111> classical Ising model, naively expected to describe this system at low temperatures. Using the random phase approximation to take into account fluctuations between the ground state doublet and the first excited doublet, we successfully describe the elastic neutron scattering pattern and dispersion relations in Tb2Ti2O7, semi-quantitatively consistent with experimental observations. 
Ying-Jer Kao, Matthew Enjalran, Adrian Del Maestro, Hamid R. Molavian,   Michel J.P. Gingras