A new phenomenon of quantum-dot cellular automata

If an external point charge and the movable charges of an isolated quantum-dot cellular automata (QCA) cell have the same polarity, the point charge greatly affects the polarization (P) of the cell only when it is in a narrow band with periodically changing width. The center of the band is on a radius R circle. The ratio of R to the electric charge (q) is a constant determined by the parameters of the cell. A QCA cell can be used as charge detector based on the above phenomenon.

二元合金金属-绝缘转变的理论研究

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。