Power-law spin correlations in the pyrochlore antiferromagnet Tb ₂Ti ₂O ₇

We investigate the low-temperature state of the rare-earth pyrochlore Tb ₂Ti ₂O ₇ using polarized neutron scattering. Tb ₂Ti ₂O ₇ is often described as an antiferromagnetic spin liquid with spin correlations extending over lengths comparable to individual tetrahedra of the pyrochlore lattice. We confirm this picture at 20 K but find that at 0.05 K the data contain evidence of pinch-point scattering, suggesting that the low temperature state of Tb ₂Ti ₂O ₇ has power-law spin correlations.