T. Venkatesan, Rajeshwar Sharma, Ramamoorthy Ramesh, Yang Zhao, Insik Jin, Satish Ogale, M. Rajeswari, Hua Zhang, J. Liu, Wei-Kan Chu, Boyd Veal, Arvydas Paulikas, H. Zheng, Chi Lee, Wei-lou Cao, J. Li, G. Baskaran
Two novel experiments, one concerned with the fast optical response related to Cooper pair breaking using femto-second laser pulses in YBCO films and the second related to uncorrelated dynamic distortions as a function of oxygen concentration for YBCO single crystals by ion channeling, have provided information that may be relevant for understanding the mechanism of superconductivity in high Tc superconductors. In the first case a dramatic resonant photon energy dependence around 1.5 eV in the pair breaking rate has been observed, suggesting that an intermediate excitation may be playing an important role in the depairing process. In the second experiment, ion channeling investigations in YBa2Cu3O7-(delta ) ((delta) equals 0.05 to 0.8) crystals have clearly shown an evolution of the lattice from that of a Debye solid for (delta) equals 0.8 to one exhibiting significant lattice coherence even at much higher temperatures than Tc, with discontinuities which track Tc. These two experimental results are discussed in the light of different mechanisms including the formation of Zhang-Rice singlet or other mechanisms that lead to a non local hole.
High T 1.2-3 superconductor thin films have been deposited on (001) single crystal Si with
and without oxide bather by pulsed excimer laser evaporation technique. The oxide barrier of Zr02 was
also deposited by the same laser technique. It is shown that the quality of superconductor film and the
corresponding transition depend on the quality of the barrier layer. Low angle X-ray diffraction and IR
transmission results have been used to identify the structural quality of the barrier layer. The
superconducting films have been characterized using X-ray diffraction and resistivity-temperature
measurements. T0 of 87K has been achieved in O.7p.m thick high T films on Si with O.3p.m thick
Z102 barrier deposited at 600°C.
High T 1-2-3 superconductor thin films have been deposited on (001) single crystal Si with
and without oxide barrier by pulsed excimer laser evaporation technique. The oxide barrier of Zi02 was
also deposited by the same laser technique. It is shown that the quality of superconductor film and the
corresponding transition depend on the quality of the barrier layer. Low angle X-ray diffraction and IR
transmission results have been used to identify the structural quality of the barrier layer. The
superconducting films have been characterized using X-ray diffraction and resistivity-temperature
measurements. T of 87K has been achieved in O.7p,m thick high T films on Si with O.3p.m thick
Z1O2 bather deposited at 600°C.
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