Recoupling of Decoupled Vortex Liquid by Columnar Defects inBi2Sr2CaCu2O8+y

Abstract

We report on the effect of columnar defects on the interlayer phase coherence in ${\mathrm{Bi}}_{2}{\mathrm{Sr}}_{2}{\mathrm{CaCu}}_{2}{\mathrm{O}}_{8+y}$ using Josephson plasma resonance as a probe. In the vortex liquid phase close to ${T}_{c}$, the resonance field ( ${H}_{p}$) shows a characteristic exponential temperature dependence similar to that of the irreversibility line. A drastic increase in ${H}_{p}$ occurs at a frequency-dependent temperature in the vortex liquid phase. We interpret this change as a manifestation of field-induced recoupling of decoupled vortex liquid by columnar defects. The double resonance peaks observed in this temperature range indicate the coexistence of coupled and decoupled vortex regions.