Antiferromagnetic spin ice correlations at (1/2,1/2,1/2) in the ground state of the pyrochlore magnet Tb2Ti2O7

We present high-resolution single-crystal time-of-flight neutron scattering measurements on the candidate quantum spin liquid pyrochlore Tb2Ti2O7 at low temperature and in a magnetic field. At similar to 70 mK and in zero field, Tb2Ti2O7 reveals diffuse magnetic elastic scattering at (1/2, 1/2, 1/2) positions in reciprocal space, consistent with short-range correlated regions based on a two-in, two-out spin ice configuration on a doubled conventional unit cell. This elastic scattering is separated from very low-energy magnetic inelastic scattering by an energy gap of similar to 0.06-0.08 meV. The elastic signal disappears under the application of small magnetic fields and upon elevating temperature. Pinch-point-like elastic diffuse scattering is observed near (1,1,1) and (0,0,2) in zero field at similar to 70 mK, in agreement with Fennell et al. [Phys. Rev. Lett. 109, 017201 (2012)], supporting the quantum spin ice interpretation of Tb2Ti2O7. DOI: 10.1103/PhysRevB.87.094410