First order ferromagnetic phase transition in the low electronic density regime of a biased graphene bilayer

TL;DR

This paper investigates the phase diagram of biased graphene bilayers, revealing a first-order ferromagnetic transition driven by doping, with distinct magnetization and electronic characteristics in each layer.

Contribution

It provides the first analysis of a first-order ferromagnetic phase transition in biased graphene bilayers at low electronic densities.

Findings

First-order phase transition between paramagnetic and ferromagnetic phases.

Unequal magnetization in the two graphene layers.

Layer-specific electron and hole-like electronic densities.

Abstract

The phase diagram of a biased graphene bilayer is computed and the existence of a ferromagnetic phase is discussed both in the critical on-site interaction $U_{c}$ versus doping density and versus temperature. We show that in the ferromagnetic phase the two planes have unequal magnetization and that the electronic density is hole like in one plane and electron like in the other. We give evidence for a \emph{first-order} phase transition between paramagnetic and ferromagnetic phases induced by doping at zero temperature.