一维扩展离子Hubbard模型的相图研究∗

摘要

应用密度矩阵重整化群方法，研究了存在交错离子势∆时一维半满扩展Hubbard模型的相图。通过计算关联函数、结构因子、位置算符等方法，描绘了从Mott绝缘体-键有序绝缘体-Band绝缘体的特性并给出了精确的相边界。研究发现：中间的键有序绝缘体相在相图中占据了很小的一部分区域，当存在离子势∆的情况下，这个区域将会有所增大；而当相互作用足够强时，这个中间相消失。给出了离子Hubbard模型(最近邻电子-电子相互作用V =0)的相图。%We use a density-matrix renormalization group method to study quantitatively the phase diagram of the half-filled one-dimensional (1D) extended Hubbard model in the presence of a staggered ionic potential∆. An extensive finite-size scaling analysis is carried out on the relevant structure factors and localization operator to characterize the Mott-insulator (MI)-bond-ordered insulator (BOI)-band-insulator (BI) transitions. The intermediate BOI phase occupies a small region of the phase diagram, and this region is enlarged in the presence of∆. In addition, the phase diagram of ionic Hubbard (the nearest-neighbor electron-electron interaction V =0) is also given.