Energy scale of the electron-boson spectral function and superconductivity in NpPdAl

Ummarino, G. A.*; Caciuffo, R.*; Chudo, Hiroyuki ; Kambe, Shinsaku  

The energy scale of the electron-boson spectral function in the heavy-fermion, -wave superconductor NpPdAl is predicted on the basis of Eliashberg theory calculations. Assuming a spectral function shape typical for antiferromagnetic spin fluctuations, and imposing constraints provided by the experimental values for the critical temperature and the low-temperature energy gap, one obtains values of of about 2-2.5 meV, slightly dependent from the strength of the Coulomb pseudopotential. These values are in excellent agreement with the characteristic magnetic fluctuations energy estimated from NMR measurements of the nuclear-spin-lattice relaxation time at the Al site. The calculated temperature dependence of the upper critical field, the local spin susceptibility, and the nuclear spin-lattice relaxation rate is also in good agreement with available experimental data.