J. Phys. I France
Volume 2, Numéro 5, May 1992
Page(s) 517 - 522
DOI: 10.1051/jp1:1992162
J. Phys. I France 2 (1992) 517-522

Conductivity coherence peak in YBa 2Cu 3O 7

O. Klein1, K. Holczer1, G. Grüner1 and G.A. Emelchenko2

1  UCLA, Department of Physics, Los Angeles, CA 90024, U.S.A.
2  Academy of Sciences, 142432 Chernogolovka, Moscow, Russia

(Received 20 January 1992, accepted in final form 6 March 1992)

We have measured both the surface resistance $R_{\rm s}$ and the surface reactance $X_{\rm s}$ of a YBa 2Cu 3O 7 single crystal at millimeter wave frequencies and have evaluated the conductivity $\sigma_1$. We observe a narrow coherence peak below $T_{\rm c}$ which indicates s-wave pairing with a rapid opening of the single particle gap.

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