低维磁性系统中的量子相变及无序的影响

By using the bosonization, path integral perturbation and renormalization group methods, we have investigated the quantum phase transitions and the effects of impurity in low dimensional magnetic systems. The Peierls transition of one dimensional interacting fermion system is studied, it is pointed out that in the adiabatic limit, the ground state of this system is always dimerized. In the study of the dynamical structure of phonons in the spin-Peierls materials, it is recognized that there are soft mode and central peak mode, the condition of the phonon dynamics being in the central peak regime or the soft mode regime is obtained. The influence of the external magnetic field is also discussed. For the ladder system with two coupled quantum spin chains, we have obtained an effective gauge field theory to describe the low energy excitations of the system. For the one dimensional fermion system with impurities, we have studied its ground state and the phase diagram.

本项目拟应用共形场论、重整化群、玻色化及泛函分析方法，研究准----维和梯形结构系统中的量子相变。探讨其低温时电导率，磁化率等物理性质。进一步研究这些系统中存在杂质的随机分布而产生的无序对其相变行为及低温特性的影响。本项目应用低维量子场论中的最新成果研究低维凝聚态物理中的非微扰性质，具有重要的理论价值又有实际材料系统有直接联系．