Electron renormalization of sound interaction with two-level systems in   superconducting metglasses
  The crossing of temperature dependences of the sound velocity in normal and superconducting state of metallic glasses points out unambiguously the renormalization of the intensity of sound interaction with two-level systems (TLS), caused by their coupling with electrons. We propose a simple scenario which allows us to describe qualitatively the influence of the superconducting transition on the sound velocity and attenuation in superconducting metglasses and to make quantative estimations of renormalization parameters. 
E.V. Bezuglyi (1), A.L. Gaiduk (1), V.D. Fil (1), W.L. Johnson (2), G.   Bruls (3), B. Luethi (3), B. Wolf (3), S. Zherlitsy...