6533b839fe1ef96bd12a6312

RESEARCH PRODUCT

Frequency-dependent relaxation rate in superconductingYBa2Cu3O6+δ

subject

description

The submillimeter-wave $3 {\mathrm{cm}}^{\ensuremath{-}1}l\ensuremath{\nu}l40 {\mathrm{cm}}^{\ensuremath{-}1}$ complex conductivity of the reduced ${\mathrm{YBa}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{6+\ensuremath{\delta}}$ film ${(T}_{C}=56.5 \mathrm{K})$ was investigated for temperatures $4 \mathrm{K}lTl300 \mathrm{K}$ and compared to the properties of the same film in the optimally doped state. The frequency dependence of the effective quasiparticle scattering rate $1/{\ensuremath{\tau}}^{*}(\ensuremath{\nu})$ was extracted from the spectra. $1/{\ensuremath{\tau}}^{*}$ is shown to be frequency independent at low frequencies and high temperatures. A gradual change to $1/{\ensuremath{\tau}}^{*}\ensuremath{\propto}{\ensuremath{\nu}}^{1.75\ifmmode\pm\else\textpm\fi{}0.3}$ law is observed as temperature decreases. In order to explain the observed temperature dependence of the low frequency spectral weight above ${T}_{c},$ the quasiparticle effective mass is supposed to be temperature dependent for $Tg{T}_{c}.$