Metal-Insulator transition in one-dimensional Hubbard superlattices

TL;DR

This paper investigates the metal-insulator transition in one-dimensional Hubbard superlattices, revealing how the insulating electron density depends on free layer size and identifying universal features of the charge gap.

Contribution

It introduces a detailed analysis of the transition in Hubbard superlattices, combining numerical and strong coupling approaches to uncover new insights.

Findings

Insulating electron density increases with free layer size.

Charge gap exhibits universal features.

Interaction mechanism resembles superexchange.

Abstract

We study the Metal-Insulator transition in one-dimensional Hubbard superlattices (SL's), modelled by a repeated pattern of repulsive (i.e., positive on-site coupling) and free sites. The evolution of the local moment and of the charge gap (calculated from Lanczos diagonalization of chains up to 18 sites), together with a strong coupling analysis, show that the electron density at which the system is insulating increases with the size of the free layer, relative to the repulsive one. In the insulating state, the mechanism of interaction between fermions separated by a free layer is the analog of superexchange, and the charge gap display universal features.