Electron-phonon coupling origin of the resistivity in YNi2B2C single crystals

Resistivity measurements from 4.2 K up to 300 K were made on YNi2B2C single crystals with T-c =15.5 K. The resulting rho (T) curve shows a perfect Blo ch-Gruneisen (BG) behavior, with a very small residual resistivity which in dicates the low impurity content and the high cristallographic quality of t he samples. The value lambda (tr) =0.53 for the transport electron-phonon c oupling constant was obtained by using the high-temperature constant value of d rho /dT and the plasma frequency reported in literature. The BG expres sion for the phononic part of the resistivity rho (ph)(T) was then used to fit the data in the whole temperature range, by approximating alpha (2)(tr) (Omega) with the experimental phonon spectral density G(Omega) multiplied b y a two-step weighting function to be determined by the fit. The resulting fitting curve perfectly agrees with the experimental points. We also solved the red-axis Eliashberg equations in both s- and d-wave symmetries under t he approximation alpha F-2(Omega) approximate to alpha F-2(tr)(Omega). We f ound that the value of lambda (tr) here determined in single-band approxima tion is quite compatible with T-c and the gap Delta experimentally observed . Finally, we calculated the normalized tunneling conductance, whose compar ison with break-junction tunnel data gives indication of the possible s-wav e symmetry for the order parameter in YNi2B2C.