MAGNETIC PENETRATION DEPTH IN HIGH-TC SUPERCONDUCTING TL2CA1BA2CU2O8-DELTA SINGLE-CRYSTALS

The temperature dependence of Cu-O plane magnetic penetration depth, lambda(ab)(T), for Tl-2122 single crystals has been determined by measuring the low-field d.c. magnetization using a SQUID susceptometer. Almost full (97%) diamagnetism at low temperature was reached by carefully minimizing the background field, which is an essential condition for this method. lambda(ab)(0) was obtained uniquely by a self-consistent condition to be 182 nm. Results of our measurements show a deviation from the single-band BCS s-wave prediction. The exponential behavior in very limited temperature regions may be reconciled with the BCS-like prediction. However, our lambda(T) data follow the theoretical prediction very accurately for a p-wave polar state pairing.