Low Temperature Physics: 32, 489 (2006); https://doi.org/10.1063/1.2199452 (8 pages)
Физика Низких Температур: Том 32, Выпуск 4-5 (Апрель 2006), c. 641-650    ( к оглавлению , назад )

Investigation of the superconducting energy gap in the compound LuNi2B2C by the method of point contact spectroscopy: two-gap approximation

N.L. Bobrov, S.I. Beloborod`ko, L.V. Tyutrina, V.N. Chernobay, and I.K. Yanson

B. Verkin Institute for Low Temperature Physics and Engineering of the National Academy of Sciences of Ukraine, 47 Lenin Ave., Kharkov 61103, Ukraine
E-mail: bobrov@ilt.kharkov.ua

D.G. Naugle and K.D.D. Rathnayaka

Department of Physics, Texas A&M University, College Station TX 77843-4242, USA

Received October 26, 2005

Аннотация

It is shown that the two-gap approximation is applicable for describing the dV/dI(V) spectra of LuNi2B2C–Ag point contacts in a wide interval of temperatures. The values and the temperature dependences of the large and the small gaps in the ab plane and in the c direction were estimated using the generalized BTK model [A. Plecenik, M. Grajacar, S. Benacka P. Seidel, A. Pfuch, Phys. Rev. B49, 10016 (1994)]] and the equations of [S.I. Beloborodko, Fiz. Nizk. Temp. 29, 868 (2003) [Low Temp. Phys. 29, 650 (2003)]. In the BCS extrapolation the critical temperature of the small gap is 10 K in the ab plane and 14.5 K in the c direction. The absolute values of the gaps are D0ab = 2.16 meV and D0c = 1.94 meV. For the large gaps the critical temperature Tc coincides with the bulk, Tcbulk = 16.8 K, and their absolute values are very close, being about 3 meV in both orientations. In the c direction the contributions to the conductivity from the small and the large gaps remain practically identical up to 10–11 K. In the ab plane the contribution from the small gap is much smaller and decreases rapidly as a temperature rises.

PACS:
63.20.Kr - Phonon-electron and phonon-phonon interactions
72.10.Di - Scattering by phonons, magnons, and other nonlocalized excitations (see also 71.45.-d Collective effects in electronic structure of bulk materials)
73.40.Jn - Metal-to-metal contacts

Ключевые слова: point contacts, two-gap approximation.