摘要:
本文通过二次矩M2（t）和概率分布Wn（t）数值地研究了两种扩展Harper模型的波包动力学,得到了这两种模型中各个相、各条临界线以及三相点的波包扩散情况.对于第一种扩展Harper模型,发现两个金属相中波包是弹道扩散的,在绝缘体相中波包不扩散,而在三相点以及各条临界线上波包是反常扩散的.同时,发现金属相—金属相转变的临界线上的波包动力学行为与金属相—绝缘体相转变的临界线上的相同,但三相点的动力学行为与各临界线上的不同;对于第二种扩展Harper模型,发现金属相中波包是弹道扩散的,在绝缘体相中波包不扩散,而在临界相、三相点、以及各条临界线上波包是反常扩散的.同时,发现临界相—金属相转变的临界线上的波包动力学行为与三相点、临界相—绝缘体相转变的临界线上的相同,但与金属相—绝缘体相转变的临界线上的不同.
Abstract:
We study the wave packet dynamics of two extended Harper models by using the second moment M2（t）and probability distribution Wn（t） numerically. The dynamical behaviors of two extended Harper models in all phases, on all phase boundary lines, and at the bicritical points are studied. For the first extended Harper model, we find that the wave packet is of ballistic diffusion in two metal phases, localized in the insulator phase, and of anomalous diffusion on the phase boundary lines and at the bicritical point. We also find the dynamical behavior on the boundary line of the metal-metal phase transition is the same as that on the metal-insulator phase transition. The spreading at the bicritical point is different from that on the phase boundary lines. For the second extended Harper model, we find that the wave packet is of ballistic diffusion in the metal phase, localized in the insulator phase, and of anomalous diffusion in the critical phase, on the phase boundary lines, and at the bicritical point. We also find the dynamical behavior on the boundary line of the critical-metal phase transition is similar to that at the bicritical point and the critical-insulator phase transition, but different from that of the metal-insulator phase transition.
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