Abstract

This work determines the electron scattering rate in the a-b plane of epitaxial YBa2Cu3O7 films using two techniques.  Infrared spectroscopy yields the scattering rate at temperatures of 10, 78, and 300K by fitting reflectance data using thin-film optics and a model for the free-carrier conductivity.  The scattering rate is also obtained using kinetic theory and an extrapolation of normal-state electrical resistvity data to superconducting temperatures based on the Bloch theory for the phonon-limited electrical resistivity of metals.  The scattering rates determined using both techniques are in agreement and show that the electron mean free path in the a-b plane of YBa2Cu3O7 superconducting films is three to four times the coherence length.  Hence YBa2Cu3O7 is pure but not in the extreme pure limit.  An average defect interaction range of 4 nm is obtained using the defect density resulting from flux-pinning considerations.