Study of Microstructure and Local Electron Structure of Zn-Doping GdBa_2Cu_3O_(7-δ) Systems Using Positron Experiment

摘要

The Zn-doped GdBa_2Cu_(3-x)Zn_xO_(7-δ) (x = 0.00-0.40) superconductors have been systemically investigated by structural analysis and positron lifetime. The structural results show that the lattice parameter a and b increase slightly with increasing Zn content x, and the parameter c has a small abrupt decrease. Based on the Jahn-Teller model, we analyze the results of structural distortion. From the positron lifetime data, the local electron density n_e has been calculated and the result implies a redistribution of electrons between the Cu-O chains and the CuO_2 planes, resulting in the carrier localization. Furthermore, combining the results of the electronic density n_e and the transition temperature T_c with Zn doping content, it suggests that the carrier localization could interfere the pairing and the "charge transfer" between Cu-O chains and the CuO_2 planes and then suppresses superconductivity of the systems.