Mechanism of Tc enhancement in Cu1−xTlx-1234 and -1223 system with Tc > 130 K

Abstract A new Tc enhancement method, a combination of alloying of Cu- and Tl-system and selective reduction for hole-doping has been developed for Cu 1−x Tl x Ba 2 Ca 3 Cu 4 O 12−y (Cu 1−x Tl x -1234) and Cu 1−x Tl x Ba 2 Ca 2 Cu 3 O 10−y (Cu 1−x Tl x -1223) system. The method is very effective for the Tc enhancement up to 132 K for Cu 1−x Tl x -1223 and 126 K for Cu 1−x Tl x -1234( x =0.4∼0.9). A new concept of band degeneration effect is proposed as the Tc enhancement mechanism for a common optimum hole-doping in every CuO 2 layers.