Charge dynamics and optical properties of layered cobaltates

We study the charge dynamics and electronic structure by optical spectroscopy technique. Here we focus on the following four issues: (1) the evolution of optical spectra with Na content; (2) the spectral features specific to different regions in the phase diagram; (3) the c  -axis optical response for crystal at the A-type antiferromagnetic region; (4) the optical response of misfit-layered Bi2M2Co2OyBi2M2Co2Oy (M=BaM=Ba, Sr, Ca) and Ca3Co4OyCa3Co4Oy single crystals.