Three dimensionality of band structure and a large residual quasiparticle population in Ba₀.₆₇K₀.₃₃Fe₂As₂ as revealed by the c-axis polarized optical measurement

الأصل · EN

We report on a c-axis polarized optical measurement on a Ba₀.₆₇K₀.₃₃Fe₂As₂ single crystal. We find that the c-axis optical response is significantly different from that of high-Tc cuprates. The experiments reveal an anisotropic three-dimensional optical response with the absence of the Josephson plasma edge in R(ω) in the superconducting state. Furthermore, different from the ab-plane optical response, a large residual quasiparticle population down to T 1/5Tc was observed in the c-axis polarized reflectance measurement. We elaborate that there exist nodes for the superconducting gap in regions of the 3D Fermi surface that contribute dominantly to the c-axis optical conductivity.