The Tb$_2$Ti$_2$O$_7$ pyrochlore magnetic material is attracting much attention for its { \em spin liquid} state, failing to develop long range order down to 50 mK despite a Curie-Weiss temperature $\theta_{ \rm CW} \sim -14$ K. In this paper we reinvestigate the theoretical description of this material by considering a quantum model of independent tetrahedra to describe its low temperature properties. The naturally-tuned proximity of this system near a N\'eel to spin ice phase boundary allows for a resurgence of quantum fluctuation effects that lead to an important renormalization of its effective low energy spin Hamiltonian. As a result, Tb$_2$Ti$_2$O$_7$ is argued to be a { \em quantum spin ice}. We put forward an experimental test of this proposal using neutron scattering on a single crystal.
Categories: cond-mat.stat-mech cond-mat.mtrl-sci