Persistent currents in mesoscopic rings: A numerical and renormalization group study

TL;DR

This study uses advanced numerical and renormalization group techniques to analyze persistent currents in interacting electron rings with impurities, revealing how interactions and impurities suppress current and validating the methods' effectiveness.

Contribution

It demonstrates the effectiveness of combined DMRG and functional RG methods in studying persistent currents in interacting, impurity-laden mesoscopic rings, especially for large systems.

Findings

Persistent current vanishes faster than 1/N with interactions and impurities.

Results agree with bosonization predictions for large systems and impurities.

Functional RG is validated as a powerful tool for correlated electron systems.

Abstract

The persistent current in a lattice model of a one-dimensional interacting electron system is systematically studied using a complex version of the density matrix renormalization group algorithm and the functional renormalization group method. We mainly focus on the situation where a single impurity is included in the ring penetrated by a magnetic flux. Due to the interplay of the electron-electron interaction and the impurity the persistent current in a system of N lattice sites vanishes faster then 1/N. Only for very large systems and large impurities our results are consistent with the bosonization prediction obtained for an effective field theory. The results from the density matrix renormalization group and the functional renormalization group agree well for interactions as large as the band width, even though as an approximation in the latter method the flow of the two-particle vertex is neglected. This confirms that the functional renormalization group method is a very powerful tool to investigate correlated electron systems. The method will become very useful for the theoretical description of the electronic properties of small conducting ring molecules.