Summary: PhyslcaC 235-240 (1994~ 1"33-1734
High Resolution Inelastic Neutron Scattering Study of Phonon Seli-Energy
Effects in YBCO.
D. Reznika, B. Keirnerb, F. Doganc, and I.A. Aksayc,
a National Institute of Standards and Technology, Gaithersburg MD 20899,
b Dept. of Physics, Princeton University, Princeton, N-J08544,
c Dept. of Chemica! Engineering, Princeton, University, Princeton, NJ 08544.
We report preliminary results of the high resolution melastic neutron scattering
measurements of the 42.5 meV optical phonon branch in YBCO, whose behavior at
momentum transfer q=0 has been extensively studied by Raman scattering. The experiment
was done on a large (75g) single crystal of YBa2Cu307-x (Tc~90K) with the resolution of 2
meV (full width at half maximum). In cooling from 100Kto 50K we observe a small softening
of the phonon energy at q=0.25,0.25,0, but no significant linewidth change.
It is well known that phonon self-energy
effects in superconductors provide
information about electron-phononcoupling
and the magritude and the phase of the
superconducting e:,ergy gap. 17-3Electrgnlc
contribution to the phonon self-energy is