From dia- to paramagnetic orbital susceptibility of Dirac cones

TL;DR

This paper investigates how the orbital magnetic response of systems with Dirac points varies from diamagnetic to paramagnetic, depending on the Berry phase, using a lattice model that interpolates between known limits.

Contribution

It introduces a lattice model that smoothly transitions between diamagnetic and paramagnetic responses in Dirac systems, linking this behavior to Berry phase variations.

Findings

Graphene exhibits diamagnetism at zero energy.

Dice lattice shows paramagnetism at zero energy.

The model demonstrates a continuous transition in magnetic response.

Abstract

We study the orbital susceptibility of coupled energy bands with a pair of Dirac points, as in graphene. We show that different systems having the same zero-field energy spectrum exhibit strong differences in their orbital magnetic response at zero energy, ranging from diamagnetism (graphene) to paramagnetism (dice lattice). A lattice model is introduced which interpolates continuously between these two limits. This striking behavior is related to a Berry phase varying continuously from pi to 0. These predictions could be tested with cold atoms in an optical lattice