Josephson plasma resonance in Bi2Sr2CaCu2O8+gamma with partially introduced columnar defects

We study the Josephson plasma resonance in BiSr2CaCu2O8+y single crystals w ith columnar defects (CDs) which are partially introduced in a controlled w ay. When the CDs are introduced into the crystal, either into the half of t he ab-plane or the half along the c-axis, we observe multiple resonance pea ks, one from the unirradiated and the others from the irradiated part. The resonance field, however, depends on which half part is irradiated. As the size of the irradiated and unirradiated part decreases, the resonance from the unirradiated part is strongly suppressed. These results are interpreted by assuming the phase correlation length, which determines the spatial ext ent over which the phase coherence is averaged, is semi-macroscopic in the ab-plane and shorter than 20 mum along the c-axis. (C) 2001 Elsevier Scienc e B.V. All rights reserved.