Ferromagnetic instability and finite-temperature properties of two-dimensional electron systems with van Hove singularities

TL;DR

This paper investigates ferromagnetic tendencies and finite-temperature properties of two-dimensional electron systems near van Hove singularities using a functional renormalization-group approach, revealing a dome-shaped phase diagram with incommensurate magnetism and triplet p-wave superconductivity.

Contribution

It introduces a detailed analysis of ferromagnetic instability and superconductivity near van Hove filling in the 2D Hubbard model using FRG, highlighting asymmetric magnetic behavior and phase diagram features.

Findings

Ferromagnetic tendency occurs in a dome-shaped region around van Hove filling.

Incommensurate magnetism is favored near the edge of the dome above van Hove filling.

Triplet p-wave superconductivity develops at low temperatures inside the dome.

Abstract

We study a ferromagnetic tendency in the two-dimensional Hubbard model near van Hove filling by using a functional renormalization-group method. We compute temperature dependences of magnetic susceptibilities including incommensurate magnetism. The ferromagnetic tendency is found to occur in a dome-shaped region around van Hove filling with an asymmetric property: incommensurate magnetism is favored near the edge of the dome above van Hove filling whereas a first-order-like transition to the ferromagnetic ground state is expected below van Hove filling. The dome-shaped phase diagram is well captured in the Stoner theory by invoking a smaller Coulomb interaction. Triplet p-wave superconductivity tends to develop at low temperatures inside the dome and extends more than the ferromagnetic region above van Hove filling.