Superconducting gap anisotropy probed by ultrasonic attenuation

本文测量了高各向异性g波超导体YNi_2B_2C在所有对称独立弹性模下的超声衰减α，以探索费米面上超导零能隙区的位置。在超导态下，纵模的衰减表现出明显的各向异性：α沿着[110]和[001]方向表现出热激活行为，而沿着[100]方向表现出非线性依赖性。这些结果与横模的结果一起证明了沿[100]和[010]方向沿着存在点节点或零间隙区域。这清楚地表明了超声衰减作为各向异性超导间隙结构的强有力探针。

Ultrasonic attenuation a of highly anisotropic g-wave superconductor YNi_2B_2C has been measured for all the symmetrically independent elastic modes, to explore the location of zero superconducting gap region on the Fermi surface. The attenuation of longitudinal mode shows pronounced anisotropy i n the superconducting state : While a shows thermally activated behavior along [110] and [001], it shows -linear dependence along [100]. These results together with those for the transverse modes demonstrate the presence of point nodes or zero-gap regions along [100] and [010] directions. This is a clear demonstration of ultrasonic attenuation as a powerful probe for the structure of anisotropic superconducting gap.