Field Dependence of Superfluid Density in β-PdBi2.

Specific heat and small-angle neutron scattering measurements have been performed on the superconductor β-PdBi₂. Whereas models with a uniform gap do not yield an adequate description of the temperature-dependent specific heat and the temperature and magnetic field dependence of the SANS intensity, fits to a heuristic model with two gap parameters agree well with both data sets. The fact that two parameters are required indicates a momentum-dependent gap anisotropy and/or gaps of different magnitude on different Fermi surface sheets. Fits to this model indicate that the ratio of the two gap parameters increases as a function of increasing field. [ABSTRACT FROM AUTHOR]