结构调制对Bi_2Sr_2CuO_6电子结构的影响

EFFECT OF STRUCTURAL MUDULATION ON ELECTRONIC STRUCTURE OF Bi_2Sr_2CuO_6

在铋基超导体中,Bi-O,Sr-O和CuO_2层的结构畸变导致了原子偏离理想位置,形成更有利的成键环境。这种原子几何位置的改变在计算其电性质时必须予以考虑。但至今对其进行的电子结构计算都是基于Bi-O层具有理想NaCl型结构。考虑畸变在内的详细电子结构计算有助于了解调制的起因以及这些材料复杂的物理化学特征。因此本文对Bi_2Sr_2CuO_6进行了紧束缚带计算,探讨了结构调制对电子态和化学键性质的影响。

Tight-binding band calculations of the Extended Huckel type were performed on the modulated Bi_2Sr_2CuO_6 sublattice in contrast with those for the average structure. It is shown that the structural modulation weakens Bi-O autibonding interactions, leading to a splitting of Bi 6P states and a shift of Bi 6p-block bands toward lower energy region. Such a shift favors the formation of the electron pocket of the Bi 6p-block bands thereby strengthening the oxidation of the CuO2 sheets.