Dynamics of a quantum particle in low-dimensional disordered systems with extended states

Abstract

We investigate the dynamics of a quantum particle in disordered tight-binding models in one and two dimensions which are exceptions to the common wisdom on Anderson localization, in the sense that the localization length diverges at some special energies. We provide a consistent picture for two well-known one-dimensional examples: the chain with off-diagonal disorder and the random-dimer model. In both cases the quantum motion exhibits a peculiar kind of anomalous diffusion which can be referred to as bi-fractality. The disorder-averaged density profile of the particle becomes critical in the long-time regime. The qth moment of the position of the particle diverges with time whenever q exceeds some q0. We obtain q0 = 2 for off-diagonal disorder on the chain (and conjecturally on two-dimensional bipartite lattices as well). For the random-dimer model, our result q0 = 1/2 corroborates known rigorous results.

Locations

• Journal of Statistical Mechanics Theory and Experiment - View
• arXiv (Cornell University) - View - PDF
• DataCite API - View