In the vortex liquid state the Josephson plasma frequency ωp is strongly affected by fluctuations in the vortex pancakes. We have measured in detail the variation of ωp with field B and tilt angle θ in Bi2Sr2CaCu2O8. We compare the data with Koshelev's expression relating ωp to the correlation function of the local phase S1. The agreement is quite close for θ > 1°, provided f varies with B with a weak exponent (f measures the number of pancakes within a correlated area). A scattering picture is introduced to clarify how the plasma resonance is equivalent to a Fourier transform of |S1|2 . From the fit, we find that, at 50 K and 1 T, f ≈ 1.4 pancakes, Jc0 equals 4160 A/cm2 and 〈cos φn,n+1〉 = 0.028. Deviations observed when B is aligned with the planes are discussed.
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics
- Energy Engineering and Power Technology
- Electrical and Electronic Engineering