Study on the photo-induced oxygen reordering in YBa2Cu3O6+x

Effect of the long term illumination of the YBa2Cu3O6+x with visible light or ultraviolet irradiation on its superconducting properties was studied in the frame of a simple theoretical model, which assumes that photodoping triggers rearrangement of oxygen monomers in the chain layers thus causing the enhancement of the average chain length, l(av). Since, according to the model of charge transfer mechanism, long CuO chains are better electronic hole donors than the short ones, increase of the average chain length induces additional holes transfer from chain layers to the superconducting CuO2 planes which in turn leads to the increase of the superconducting transition temperature T-c. By the use of the expression for the chain length probability distribution and numerically calculated values for the average chain length in the non-excited system, we were able to estimate the doping p (number of holes per one Cu atom in the superconducting CuO2 planes) and T-c enhancement due to photo-induced oxygen reordering. The theoretical results are compared with available experimental data. (C) 2011 Elsevier B.V. All rights reserved.5th International Conference on Elementary Processes in Atomic Systems (CEPAS), Jun 21-25, 2011, Belgrade, Serbi

Effect of illumination on the superconducting transition temperature T-c in YBa2Cu3O6+x

In the present study, we have employed two dimensional ASYNNNI model and the numerical Monte Carlo simulations to investigate the effect of visible light or ultraviolet radiation on the doping p of the superconducting CuO2 planes, and consequently on the superconducting transition temperature T-c, in YBa2Cu3O6+x high-T-c superconductor. It was shown that, depending on the oxygen concentration, x, three regions of different critical temperatures T-c behavior could be distinguished. In the first region where x LT 0.6 the critical temperature increases rapidly with oxygen depletion, in the second region, 0.6 LT x LT 0.75, the total T-c change, delta T-c, is almost independent of the oxygen content thus forming some kind of plateau, while in the third region, 0.75 LT x LT 1.0, the T-c does not increase significantly. Such a theoretically obtained behavior of T-c is in general agreement with the experimentally established facts on the delta 7(c), vs. x dependence. (C) 2011 Elsevier B.V. All rights reserved.5th International Conference on Elementary Processes in Atomic Systems (CEPAS), Jun 21-25, 2011, Belgrade, Serbi