0000000000403164
AUTHOR
Franz Mayr
Broadband infrared conductivity in an YBa2Cu3O6.7 thin film
Infrared reflectivity of an oxygen reduced YBa2Cu3O6.7 thin film was measured in the frequency range 30 cm-1 < v < 7000 cm-1 and for temperatures 5 K < T < 300 K. At lower frequencies, 3 cm-1 < v < 40 cm-1, the complex conductivity σ*=σ1+iσ2 was measured directly using a transmission technique. Both data sets were combined to obtain the reflectivity in a broad frequency range and thus to improve substantially the quality of the Kramers-Kronig analysis at low frequencies. The analysis of the conductivity spectra reveals that the low-frequency spectral weight strongly depends on temperature directly above TC but saturates for T ≥ 150 K.
Frequency-dependent conductivity of UPd2Al3 films
The transmission of UPd2Al3 films was studied (4 K < T < 300 K) in the frequency range from 4 to 32 cm−1 by using a coherent source interferometer which allows for measuring both, amplitude and phase. In addition we report on radio frequency and optical measurements. Below 20 K the conductivity and dielectric constant show strong deviations from the behavior of a normal metal which cannot simply be explained by a single renormalized Drude model with an enhanced mass and reduced scattering rate. Instead, we find evidence for the opening of a pseudogap with a gap energy of 6 cm−1 and an extremely narrow ω = 0 mode which is responsible for the large DC conductivity.