Anomalous orbital magnetism in Dirac-electron systems: Role of pseudo-spin paramagnetism

TL;DR

This paper investigates how pseudo-spin degrees of freedom in Dirac-electron systems induce paramagnetic susceptibility, explaining the singular diamagnetism observed in gapped graphene and 3D Dirac materials.

Contribution

It reveals the role of pseudo-spin paramagnetism in orbital magnetic responses, a novel insight into Dirac-electron systems' magnetic properties.

Findings

Pseudo-spin contributes to paramagnetic susceptibility.

Singular diamagnetism occurs only in the band-gap region.

Pseudo-spin paramagnetism explains the magnetic behavior in Dirac systems.

Abstract

The orbital diamagnetic susceptibility is calculated in monolayer and bilayer graphenes with band gap as well as in three-dimensional Dirac systems. It is demonstrated that the pseudo-spin degree of freedom such as valleys produces paramagnetic susceptibility in an equal manner as the real spin dominating over the Landau diamagnetism. The pseudo-spin paramagnetism explains the origin of a singular diamagnetism which is present only in the band-gap region and disappears rapidly inside the conduction and valence bands.