Low-energy phonon excitations in superconducting RNi{sub 2}B{sub 2}C (R=Lu,Y)
- Ames Laboratory and Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011 (United States)
- The Institute of Physical and Chemical Research (RIKEN), Wako, Saitama 351-01 (Japan)
- Brookhaven National Laboratory, Upton, New York 11973-5000 (United States)
Inelastic neutron-scattering techniques have been used to study the low-energy phonon excitations in superconducting RNi{sub 2}B{sub 2}C (R=Lu, Y) to further characterize the anomalous features observed by Kawano {ital et al.} [Phys. Rev. Lett. {bold 77}, 4628 (1996)] for R=Y and Stassis {ital et al.} [Phys. Rev. B {bold 55}, R8678 (1997)] for R=Lu, when these systems enter the superconducting ground state. We find that above T{sub c} the frequencies of the {Delta}{sub 4}[{xi}00] lowest-lying acoustic and optic phonon modes decrease with decreasing temperature, for {bold {xi}} close to the nesting vector {bold {xi}}{sub m}. In addition there is a shift of intensity from the upper to the lower mode, an effect characteristic of mode coupling. The observed intensity transfer between these modes above T{sub c} can be described satisfactorily in both compounds by a coupled-mode model. Below T{sub c} the observed spectrum changes dramatically: it consists of a sharp peak at approximately 4 meV with a broad weak shoulder at higher energies. The experimental results unambiguously show that this dramatic change is due to the onset of superconductivity in these compounds. In this temperature region, the results are in qualitative agreement with recent theoretical calculations. {copyright} {ital 1998} {ital The American Physical Society}
- OSTI ID:
- 599141
- Journal Information:
- Physical Review, B: Condensed Matter, Journal Name: Physical Review, B: Condensed Matter Journal Issue: 13 Vol. 57; ISSN PRBMDO; ISSN 0163-1829
- Country of Publication:
- United States
- Language:
- English
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