Renormalization group analysis of magnetic and superconducting instabilities near van Hove band fillings

TL;DR

This paper uses renormalization group methods to analyze magnetic and superconducting phases in the 2D t-t' Hubbard model near van Hove fillings, revealing phase transitions driven by band filling and hopping parameters.

Contribution

It provides a detailed phase diagram of the model using advanced RG techniques, highlighting the competition between antiferromagnetism, ferromagnetism, and superconductivity.

Findings

Antiferromagnetism dominates at small t' and van Hove fillings.

Increasing t' leads to d-wave superconductivity replacing antiferromagnetism.

Near t'=t/2, the system favors ferromagnetism, with triplet p-wave superconductivity away from van Hove fillings.

Abstract

Phase diagrams of the two-dimensional one-band t-t' Hubbard model are obtained within the two-patch and the temperature-cutoff many-patch renormalization group approach. At small t' and at van Hove band fillings antiferromagnetism dominates, while with increasing t' or changing filling antiferromagnetism is replaced by d-wave superconductivity. Near t'=t/2 and close to van Hove band fillings the system is unstable towards ferromagnetism. Away from van Hove band fillings this ferromagnetic instability is replaced by a region with dominating triplet p-wave superconducting correlations. The results of the renormalization-group approach are compared with the mean-field results and the results of the T-matrix approximation.