YBa_2Cu_3O_z超导体的低温稳定相

LOW TEMPERATURE STABLE PHASES OF HIGH T_e SUPERCONDUCTOR YBa_2Cu_3O_z

基于8点长方集团变分模型,并引入各向同性最近邻相互作用,以及各向异性次近邻相互作用,计算了YBa_2Cu_3O_z两Ba层间铜氧平面上□—O系统的有序—无序相变图,不仅在z=7.0附近得到具有超导电性的正交相,并且在z=6.5附近得到具有两倍晶格长度的另一种正交相(正交相Ⅱ)。

Based on eight-point cluster variation method and introduction of isotropic nearest neighbor interaction and anisotropic next nearest neighbor interactions, the orderdisorder phase transition phenomena of the □-O (□: oxygen vacancy; O: oxygen) system on the copper-oxygen plane between two Ba-layers were studied. Calculation results show that there is not only a superconducting orthohombic phase (I) near z = 7.0, but also a superconducting orthohombic phase (II) near z = 6.5, as well as other metastable phases.