Study of the far-infrared and mm-wave conductivity of YBCO in the normal state

Summary

An accurate determination of the optical conductivity σ(ν) of high-T _c materials at low frequencies (ν<100 cm⁻¹) is still an open problem. In the present paper we report new far-infrared data showing that the LaAlO₃ crystal, on which high-quality YBCO films can be deposited, is well transparent at low frequencies. Test measurements have also been performed by employing the ENEA compact FEL facility; preliminary reslts indicate the possibility to obtain high-accuracy spectroscopic data in the mm-wave region. On the basis of these results, we have in program mm-wave and far-infrared transmittance measurements on thin YBCO films on LaAlO₃, in order to get new information on the low-frequency behaviour of σ(ν).