Anomalous transport through algebraically localized states in one dimension

Abstract

Localization in one-dimensional disordered or quasiperiodic noninteracting systems in the presence of power-law hopping is very different from localization in short-ranged systems. Power-law hopping leads to algebraic localization as opposed to exponential localization in short-ranged systems. Exponential localization is synonymous with insulating behavior in the thermodynamic limit. Here we show that the same is not true for algebraic localization. We show, on general grounds, that depending on the strength of the algebraic decay, the algebraically localized states can be actually either conducting or insulating in thermodynamic limit. We exemplify this statement with explicit calculations on the Aubry-Andr\'e-Harper model in the presence of power-law hopping, with the power-law exponent $\ensuremath{\alpha}>1$, so that the thermodynamic limit is well defined. We find a phase of this system where there is a mobility edge separating completely delocalized and algebraically localized states, with the algebraically localized states showing signatures of superdiffusive transport. Thus, in this phase, the mobility edge separates two kinds of conducting states, ballistic and superdiffusive. We trace the occurrence of this behavior to near-resonance conditions of the on-site energies that occur due to the quasiperiodic nature of the potential.