Persistent current in an almost staggered Harper model

• The persistent current for the Harper model is not metallic in the metallic regime.
• This stems from the nature of central band states for the staggered case.
• When the superlattice is not commensurate the persistent current is insulating.
• Even in the metallic regime Harper model may exhibit insulating current.

In this paper we study the persistent current (PC) of a staggered Harper model, close to the half-filling. The Harper model is different than other one dimensional disordered systems which are always localized, since it is a quasi-periodic system with correlated disorder resulting in the fact that it can be in the metallic regime. Nevertheless, the PC for a wide range of parameters of the Harper model does not show typical metallic behavior, although the system is in the metallic regime. This is a result of the nature of the central band states, which are a hybridization of Gaussian states localized in superlattice points. When the superlattice is not commensurate with the system length, the PC behaves as an insulator. Thus even in the metallic regime a typical finite Harper model may exhibit a PC expected from an insulator.