反绝热极限下MX链晶体中的量子晶格涨落效应:费米子自旋1/2态

相转变和对称破缺电荷密度波态的稳定性等物理特性决定于ＭＸ链系统的准一维、电子跃迁、电子－声子耦合和电子－电子相互作用。为讨论费米子自旋态ＭＸ 链系统的量子晶格涨落效应，从紧束缚Ｈａｍｉｌｔｏｎｉｓｎ模型出发，在反绝热极限条件下，采用Ｈａｒｔｒｅｅ－Ｆｏｃｋ近似，对ＭＸ链系统的电荷密度波序参量，绝缘相能隙，基态能量等进行了研究，并得到确定绝缘相能隙的自洽解方程。计算结果表明，在反绝热极限条件下，绝缘相能隙随电声子耦合强度的增大而增大，当电声子耦合强度达到临界值时，系统发生二聚化相变。

EFFECT OF QUANTUM LATTICE FLUCTUATIONS ON MX CHAIN IN ANTI~ADIABATIC LIMIT AND SPIN~1/2 CASE

The phase transition and stability of symmetry--broken charge- density-wave state of MX chain system are determined by the physical properties of quasi-one- di-mensional, electron supertransition, electron~phonon coupling, and electron-electron inter-action of MX chains. To study the effects of quantum lattice fluctuations on MX chain sys-tem in spin-1/2 case,based on the tight-binding Hamitonian model and the condition of anti--adiabatic limit,the order parameter of charge-density--wave state,the energy gap of insulator state and the ground state energy are discussed. The self-consistent equation determining the energy gap of insulator state has been attained. The result shows that in the case of anti--adiabatic limit and spin--l/2, the energy gap of insulator state increases with that of the electron-phonon coupling constant. At the critical value,the phase transition of MX chain system happens.