T. Fennell, M. Kenzelmann, B. Roessli, H. Mutka, J. Ollivier, M. Ruminy, U. Stuhr, O. Zaharko, L. Bovo, A. Cervellino, M. K. Haas, R. J. Cava
At low temperatures, Tb2Ti2O7 enters a spin liquid state, despite expectations of magnetic order and/or a structural distortion. Using neutron scattering, we have discovered that in Tb2Ti2O7 an excited crystal field level is coupled to a transverse acoustic phonon, forming a new hybrid excitation. Magnetic and phonon-like branches with identical dispersion relations can be identified, and the hybridization vanishes as Tb2Ti2O7 crosses over from the correlated, or spin liquid, state to the high temperature paramagnetic phase. We suggest that Tb2Ti2O7 is aptly named a "magnetoelastic spin liquid" and that it is the hybridization of the excitations which suppresses both magnetic ordering and the structural distortion.
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http://arxiv.org/abs/1305.5405
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