The temperature dependence between 2 and 300 K of the positron-electron annihilation lifetime and the electron momentum distribution from the Doppler-broadened annihilation gamma -ray energy spectrum were measured in the high-temperature superconducting material Tl2.2Ca2Ba 2Cu3O10.3+ delta. A temperature dependence is observed for the positron lifetime, below the critical temperature (124 K), suggestive of a dramatic decrease in the positron-electron overlap resulting from superconductivity. The magnitude of the observed change in the positron lifetime is the largest that the authors have seen for any high-Tc material, although the temperature dependence of the positron lifetime is similar to what they recently reported for YBa2Cu3O 7 and La1.85Sr0.15CuO4. The temperature dependence of the deduced electron momentum distribution indicates a complex but small variation in the number of low-momentum electrons available to annihilate with the delocalised positrons. This new experimental result further confirms the authors earlier suggestions of a common physics involved in high-Tc superconductivity for perovskite materials and provides evidence for the formation of superconducting electron states which are anti-correlated with the delocalised positron wavefunction for all classes of the new high-Tc materials.
All Science Journal Classification (ASJC) codes