Coherent terahertz spectroscopy is used to measure the complex conductivity of thin films of Bi2Sr2CaCu2O8+δ in the vortex state as a function of frequency, temperature, and applied magnetic field. We report an unusual sublinear power law dependence of the high-frequency magnetoconductivity Δσ(H) ≡ σ(H) - σ(0) on magnetic field. Over a broad range of field and temperature, Δσ2 varies as Hα, with α ≈ 1/2. We present a model based on the nonlinear London electrodynamics predicted for a d-wave superconductor which quantitatively explains these results using only parameters obtained from zero-field measurements.
ASJC Scopus subject areas
- Physics and Astronomy(all)