Observation of a collective mode in superconducting UBe13.
Published Web Locationhttps://doi.org/10.1103/physrevlett.55.2479
Sound propagation in the heavy-fermion superconductor UBe13 is studied at frequencies from 0.9 to 2.4 GHz and temperatures from 0.01 to 100 K. A peak in the acoustic attenuation is observed below the superconducting transition of 0.9 K, instead of the rapid drop expected for a BCS superconductor. Absorption into a collective mode of a nonsinglet, anisotropic superconductor is proposed. © 1985 The American Physical Society.