Low-energy phonons and superconductivity in Sn$_{0.8}$In$_{0.2}$Te
  We present neutron scattering measurements on low-energy phonons from a superconducting ($T_{c} = 2.7$~K) Sn$_{0.8}$In$_{0.2}$Te single crystal sample. The longitudinal acoustic phonon mode and one transverse acoustic branch have been mapped out around the (002) Bragg peak for temperatures of 1.7 K and 4.2 K. We observe a substantial energy width of the transverse phonons at energies comparable to twice the superconducting gap; however, there is no change in this width between the superconducting and normal states. We also confirm that the compound is well ordered, with no indications of structural instability. 
Zhijun Xu, J. A. Schneeloch, Ruidan Zhong, J. A. Rodriguez-Rivera, L.   Harriger, R. J. Birgeneau, Genda Gu, J. M. Tranquada...
cond-mat.supr-con