Temperature dependence of the Raman-active B1g and A1g modes in YNi2B2C

The Raman spectra of YNi2B2C single crystals with a superconducting transition temperature T-c=14.2 K have been measured in the temperature range 295-10 K. It turned out that the B A(1g) mode at 832 cm(-1) whose broad linewidth was previously attributed to a strong electron-phonon coupling, actually consists of two components due to the isotope effect; the frequency ratio of each component approximates to root(11)B/B-10 approximate to 1.05 of isotropic B masses. The 198 cm(-1) B-1g mode due to Ni vibrations is fitted to a Fano-Line profile, in order to derive the phonon parameters like frequency, linewidth, and asymmetry factor. The B-1g mode exhibits a normal temperature-dependent stiffening with no special change in the vicinity of T-c; it also narrows revealing a deviation from a temperature-dependent anharmonic decay and a more symmetric character from 100 K with decreasing temperature. Based on no superconductivity-induced change in frequency and Linewidth near T-c, it is concluded that there are no renormalization effects for the Ni B-1g mode, and that no strong electron-phonon coupling is operative in superconducting YNi2B2C.