Effects of disorder on two coupled Hubbard chains at half-filling

TL;DR

This paper studies how quenched disorder affects two coupled Hubbard chains at half-filling, revealing that strong disorder destroys charge and spin gaps, leading to localization, while intermediate disorder preserves some gaps.

Contribution

It provides a detailed analysis of disorder effects on coupled Hubbard chains using bosonization and RG, highlighting the conditions for gap destruction and localization.

Findings

Strong disorder destroys charge and spin gaps.

Random backward scattering induces Anderson localization.

Intermediate disorder preserves some charge gaps.

Abstract

We investigate the effects of quenched disorder on two chain Hubbard models at half-filling by using bosonization and renormalization group methods. It is found that the sufficiently strong forward scattering due to impurities and the random gauge field, which is generated by impurity backward scattering, destroy the charge gaps as well as the spin gaps. Random backward scattering due to impurities then drives the resulting massless phase to the Anderson localization phase. For intermediate strength of random forward scattering, however, the spin gaps still survive, and only one of the charge gaps is collapsed. In this parameter region, one of the charge degrees of freedom is in the Anderson localized state, while the other one is still in the massive state.