Evidence for linelike vortex liquid phase in Tl/sub 2/Ba/sub 2/CaCu/sub 2/O/sub 8/ probed using terahertz time-domain spectroscopy

Abstract

Summary form only given. To probe the vortex state in Tl/sub 2/Ba/sub 2/CaCu/sub 2/O/sub 8/ thin films we used terahertz time-domain spectroscopy in transmission. The decrease of the oscillation frequency from 70 K to 80 K in the time-domain is shown, and the effect of a magnetic field illustrated. A drop of the Josephson plasma resonance (JPR) occurs in the frequency-domain when applying a magnetic field. From the measurements we found that c-axis correlated pancake vortices are preserved across the glass transition, and that pinning is dominated by correlated disorder. We conclude that Tl/sub 2/Ba/sub 2/CaCu/sub 2/O/sub 8/ films (/spl gamma/ /spl sim/ 150), at least in the low magnetic field portion of the B-T phase diagram, behave as YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// (/spl gamma/ /spl sim/ 8) and not as Bi/sub 2/Sr/sub 2/CaCu/sub 2/O/sub 8+/spl delta// (/spl gamma/ /spl sim/ 500) single crystals, where pancake vortices disintegrate in the liquid phase, despite the closer anisotropy ratios of Bi/sub 2/Sr/sub 2/CaCu/sub 2/O/sub 8+/spl delta// and Tl/sub 2/Ba/sub 2/CaCu/sub 2/O/sub 8/.