Josephson plasma resonance in Bi 2Sr 2CaCu 2O 8+ y with partially introduced columnar defects

Abstract

We study the Josephson plasma resonance in Bi 2Sr 2CaCu 2O 8+ y single crystals with columnar defects (CDs) which are partially introduced in a controlled way. When the CDs are introduced into the crystal, either into the half of the ab-plane or the half along the c-axis, we observe multiple resonance peaks, 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 extent over which the phase coherence is averaged, is semi-macroscopic in the ab-plane and shorter than 20 μm along the c-axis.