Superconducting transition in thin films of lead telluride doped with thallium

Superconductivity has been found in 0.5-m-thick films of PbTe doped with Tl which were grown on BaF2 substrates by molecular-beam epitaxy. The observation that in the T=0 limit the ratio of the parallel to perpendicular critical magnetic fields is 1.7 suggests that the superconductivity is a bulk property. The highest value of the critical temperature was 0.6 K, which is about a factor of 2 lower than previously reported values for bulk material and polycrystalline films grown on mica substrates.