Ferromagnetism and Fermi-surface transition in the periodic Anderson model: Second-order phase transition without symmetry breaking

TL;DR

This paper investigates ferromagnetic phases and Fermi-surface topology changes in the periodic Anderson model, revealing second-order Lifshitz transitions without symmetry breaking using Gutzwiller theory.

Contribution

It demonstrates the existence of multiple ferromagnetic phases and identifies Lifshitz transitions as second-order phase transitions without symmetry breaking.

Findings

Identified three ferromagnetic phases: FM0, FM1, FM2.

Discovered Fermi-surface transitions from large to small in FM2.

Showed phase transitions are Lifshitz type without symmetry breaking.

Abstract

We study ferromagnetism in the periodic Anderson model with and without a magnetic field by the Gutzwiller theory. We find three ferromagnetic phases: a weak ferromagnetic phase (FM0), a half-metallic phase without Fermi surface for the majority spin (FM1), and a ferromagnetic phase with almost completely polarized f-electrons (FM2). The Fermi surface changes from the large Fermi-surface in the paramagnetic state to the small Fermi-surface in FM2. We also find that the transitions between the ferromagnetic phases can be second-order phase transitions in spite of the absence of symmetry breaking. While we cannot define an order parameter for such transitions in an ordinary way, the topology of the Fermi surface characterizes the transitions, i.e., they are Lifshitz transitions.