Surface impedance of Tl-2212 thin films at THz-frequencies

We report on first measurements of the surface resistance and the London penetration depth of Tl/sub 2/Ba/sub 2/CaCu/sub 2/O/sub 8/ thin films in the frequency range from 200 GHz to 1.0 THz at temperatures from 25 to 268 K carried out by time-domain Terahertz transmission spectroscopy. We observe in the superconducting state an increase of the surface resistance with the square of the frequency up to 0.9 THz at 77 K and above, At 78 K and 0.9 THz the surface resistance is 1.6 /spl Omega/. Below 77 K the surface resistance increases with the cube of the frequency. Finally, the surface resistance of Tl/sub 2/Ba/sub 2/CaCu/sub 2/O/sub 8/ is compared to that of YBa/sub 2/Cu/sub 3/O/sub 6.95/ and gold.