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 interf erometer which allows for measuring both, amplitude and phase. In addi tion 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 s ingle renormalized Drude model with an enhanced mass and reduced scatt ering rate. Instead, we find evidence for the opening of a pseudogap w ith a gap energy of 6 cm(-1) and an extremely narrow omega = 0 mode wh ich is responsible for the large DC conductivity. (C) 1998 Elsevier Sc ience B.V. All rights reserved.