  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 ~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 ~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 ~70 mK, in agreement with Fennell et al. (Ref. 1),
supporting the quantum spin ice interpretation of Tb2Ti2O7.
