Spin- and band-ferromagnetism in trilayer graphene

TL;DR

This paper investigates the ground state magnetic properties of ABA-stacked trilayer graphene, revealing conditions under which spin- and band-ferromagnetism emerge due to Coulomb interactions and multi-band structure.

Contribution

It introduces a variational approach to identify ferromagnetic instabilities in trilayer graphene considering its unique band structure.

Findings

Identification of parameter space for ferromagnetic instabilities

Demonstration of band shift due to ferromagnetic ordering

Analysis of doping and interaction strength effects

Abstract

We study the ground state properties of an ABA-stacked trilayer graphene. The low energy band structure can be described by a combination of both a linear and a quadratic particle-hole symmetric dispersions, reminiscent of monolayer- and bilayer-graphene, respectively. The multi-band structure offers more channels for instability towards ferromagnetism when the Coulomb interaction is taken into account. Indeed, if one associates a pseudo-spin 1/2 degree of freedom to the bands (parabolic/linear), it is possible to realize also a band-ferromagnetic state, where there is a shift in the energy bands, since they fill up differently. By using a variational procedure, we compute the exchange energies for all possible variational ground states and identify the parameter space for the occurrence of spin- and band-ferromagnetic instabilities as a function of doping and interaction strength.