4 research outputs found
Point-contact spectroscopy of the borocarbide superconductor YNi2B2C
Point-contact (PC) spectroscopy measurements on YNi2B2C single crystals in
the normal and superconducting (SC) state (T_c=15.4K) for the main
crystallographic directions are reported. The PC study reveals the
electron-phonon interaction (EPI) function with a dominant maximum around 12meV
and a further weak structure (kink or shallow broad maximum) at higher energy
at about 50meV. Other phonon maxima at 20, 24 and 32meV specified in the phonon
DOS of YNi2B2C by neutron measurements [PRB, V.55, 9058 (1997)] are not
resolved in the PC spectra pointing out to the main role of the low energy
phonon modes in EPI. Directional study of the SC gap results in
\Delta_[100]=1.5meV for the a- direction and \Delta_[001]=2.4meV along the
c-axis which may point to anisotropic and/or multiband behavior. Noteworthy,
the critical temperature T_c in all cases corresponds to that of bulk samples.
The value 2\Delta_[001]/kT_c=3.6 is close to the BCS one of 3.52, and the
temperature dependence \Delta(T) is BCS-like, while for the a-direction
\Delta(T) deviates from mean-field BCS behavior above T_c/2. The directional
variation in \Delta can be attributed to the multiband nature of the SC state
in YNi2B2C predicted 10 years ago (PRL, V.80, 1730 (1998)).Comment: 3 figs, 2 pages, presented on M2S-HTSC Conference, July 9-14, 2006,
Dresde
Subsurface Oxygen on Pt(111) and Its Reactivity for CO Oxidation
Catalysis and Surface Chemistr
Point-contact spectroscopy of the nickel borocarbide superconductor YNi2B2C in the normal and superconducting state
Point-contact (PC) spectroscopy measurements of YNi2B2C single crystals in
the normal and superconducting (SC) state (T_c=15.4K) for the main
crystallographic directions are reported. The PC study reveals the
electron-phonon interaction (EPI) spectral function with dominant phonon
maximum around 12 meV and further weak structures (hump or kink) at higher
energy at about 50 meV. No "soft" modes below 12 meV are resolved in the normal
state. The PC EPI spectra are qualitatively similar for the different
directions. Contrary, directional study of the SC gap results in
\Delta_[100]=1.5 meV for the a direction and \Delta_[001]=2.3 meV along the c
axis; however the critical temperature T_c in PC in all cases is near to that
in the bulk sample. The value 2\Delta_[001]/kT_c=3.6 is close to the BCS value
of 3.52, and the temperature dependence \Delta_[001](T) is BCS-like, while the
for small gap \Delta_[100](T) is below BCS behavior at T>T_c/2 similarly as in
the two-gap superconductor MgB2. It is supposed that the directional variation
\Delta can be attributed to a multiband nature of the SC state in YNi2B2C.Comment: 9 pages, 10 figures, to be published in a special issue of J. Low
Temp. Phys. in honour of Prof. H. von Loehneyse