二元合金金属-绝缘转变的理论研究

Theoretical Consideration of Metal--Insulator Transition in Binary Alloys

本文用平均场跳跃近似的方法,研究了同格点电子相关作用对 A_xB_(1-x)合金的金属-绝缘转变的影响,在两组格点能(V_A=-V_B=0.4t 和 V_A=-V_B=1.5t)和不同的相关作用 U下,得到了转变温度随浓度变化的相图。结果表明,吸引的相互作用(U<0)有利于安德森局域态的形成,当 V_A=-V_B=0.4t 时,在 x=0.5浓度附近出现了重入和双重重入现象;当 V_A=-V_B=1.5t 时,没有重入现象出现。排斤的相互作用(U>0)有利于赫伯德绝缘相的形成,但合金的无序性阻止它的形成。同时发现,在 V_A=-V_B=1.5t 时,排斥的相互作用限制和破坏安德森局域态的形成。

Studies the effect of on-site electrons' correlation on the metal-insulator tran sition in alloy A_xB_(1-x), by virtue of the mean-field hoppingapproximation. Phase diagrams showing how the transition temperature varieswith concentration are obtained under conditions that there are two groupsof site energy (V_A=-V_B=0.4t and V_A=-V_B=1. 5t)and different correlation ene-rgies(U).The results show that attractive interaction (U<0) is boneficial to theformation of Anderson's localized states.It is found that reentrancy even dualreentrancy will take place in the vicinity of the concentration at x=0.5 whenVA=-V_B=0. 4t but no reentrancy takes place when V_A=-V_B=1.5t. The repulsiveinteraction (U>0) is proved beneficial to the formation of Hubbard insulatingphase, however, the insulating phase will be inhibited by the disorder ofalloy.It is also found that the repulsive interaction will not only interferebut deform Anderson's localized states when V_A=-V_B=1.5t.