Free-carrier relaxation dynamics in the normal state of sinteredYBa2Cu3O7−y

The conductivity of $\mathrm{Y}{\mathrm{Ba}}_2{\mathrm{Cu}}_3{\mathrm{O}}_{7-y}$ in the normal state has been obtained from a measurement of the reflectivity over a wide frequency range. The product of the Drude model parameters ${\omega }_p\tau <1\mathrm{}$ indicates that the plasma oscillations are overdamped. The free-carrier electrodynamics are well described by a frequency-dependent scattering rate which rises linearly in frequency from the dc value and saturates at a value consistent with scattering at the unitarity limit with a concomitant frequency-dependent mass enhancement.