In-Plane Anisotropy of the Penetration Depth in YBa2Cu3O7-x and YBa2Cu4O8 Superconductors.

D. N. Basov,1 R. Liang,2 D. A. Bonn,2 W. N. Hardy,2 B. Dabrowski,4 M. Quijada,3 D. B. Tanner,3 J. P. Rice,5 D. M. Ginsberg,5 and T. Timusk1 1Department of Physics and Astronomy, McMaster University, Hamilton, Ontario, Canada L8S 4M1 2Department of Physics, University of British Columbia, Vancouver, British Columbia, Canada V6T 4M1 3Department of Physics, University of Florida, Gainesville, Florida 32611 4Physics Department, Northern Illinois University, DeKalb, Illinois 60115 5Department of Physics, University of Illinois, Urbana, Illinois 61801 (Received 31 May 1994)