Measurement of the Far-Infrared Magnetoconductivity Tensor of SuperconductingYBa2Cu3O7−δThin Films

We report measurements of the far-infrared transmission of superconducting ${\mathrm{YBa}}_2{\mathrm{Cu}}_3{\mathrm{O}}_{7-\delta }$ thin films from 5 to 200 ${\mathrm{cm}}^{-1\mathrm{}}$ in fields up to 14 T. A Kramers-Kronig analysis of the magnetotransmission spectrum yields the magnetoconductivity tensor which is found to be dominated by three terms: a London term, a low frequency Lorentzian $\left({\omega }_1\approx 3{\mathrm{cm}}^{-1\mathrm{}}\right)$ of width ${\gamma }_1=10\mathrm{}{\mathrm{cm}}^{-1\mathrm{}}$, and a finite frequency Lorentzian of width ${\gamma }_2=17\mathrm{}{\mathrm{cm}}^{-1\mathrm{}}$ at ${\omega }_2=24\mathrm{}{\mathrm{cm}}^{-1\mathrm{}}$ in the hole cyclotron resonance active mode of circular polarization.