Strong Increase in Ultrasound Attenuation below T c in Sr 2 RuO 4

摘要: Recent experiments suggest that the superconducting order parameter of Sr 2 RuO 4 has two components. A two-component order parameter has multiple degrees of freedom that can result in low-energy collective modes or the formation of domain walls, the dynamics of which can show up in sound attenuation experiments. We measured ultrasound attenuation across the superconducting transition of Sr 2 RuO 4 and find that the attenuation for compressional sound increases by a factor of seven immediately below T c, in sharp contrast with what is found in both conventional (s-wave) and high-T c (d-wave) superconductors. Our observations appear to be most consistent with the presence of domain walls between different configurations of the superconducting state. The formation of domains naturally explains observations such as the smallness of time reversal symmetry breaking signal at T c, and telegraph …