Infrared properties of YBa 2 Cu 3 O 7 and Bi 2 Sr 2 Ca n − 1 Cu n O 2 n + 4 thin films
Résumé
We report room-temperature optical reflectivity and transmission measurements on a variety of
YBa2Cu307 and Bi2Sr2Can -1CUn02n +4 thin films in the 500-25000 cm-1 frequency range. Reflectivity
data when not biased by the substrate are used to compute the optical conductivity. A comparison of
our results with published reflectivity data on single-domain YBa2Cu307 crystals suggests an overwhelming
contribution of the CU02 planes {with respect to the chains} to the optical conductivity. The data
can be analyzed in terms of a Drude low-frequency contribution and a so-called midinfrared band. However,
the anomalous infrared response appears to be uniquely described by a generalized Drude response:
for all the samples investigated, the relaxation rate (which increases linearly with frequency) and the
effective mass are found to be the same as a function of frequency.