Angular Dependence of Josephson Plasma Resonance in Bi2Sr2CaCu2O8+y with Columnar Defects

Abstract

Interlayer phase coherence (IPC) in Bi2Sr2CaCu2O8+y (BSCCO) with columnar defects (CDs) tilted away from the c-axis was studied by using Josephson plasma resonance (JPR). IPC in the vortex liquid state shows nonmonotonic field dependence, which we call “recoupling” of decoupled vortex liquid. When CDs are introduced along the c-axis, recoupling occurs at a characteristic field of H* = (1/5~ 1/3)BΦ, where BΦ is the matching field. When CDs are introduced at an angle, θcd, the density of CDs in each CuO2 layer decreases to BΦ eff = BΦ cosθCD, while the pinning potential is enhanced due to the increase in the size of CDs. At larger θCD, recoupling occurs at H* = (1/5~1/3)BΦ eff. This means that the recoupling is controlled only by the density of CDs in each CUO2 layer. Angular dependence of JPR field, Hp (θH), in BSCCO with θCD = 0° is smooth near θH = 0°. As θCD increases, Hp (θH) starts to show a pronounced peak near θH = θCD. These features can be qualitatively understood by rescaling the angles in anisotropic superconductors when they are converted into isotropized system.