Ferromagnetic phase in graphene-based planar heterostructures induced by charged impurity

TL;DR

This paper investigates how charged impurities in graphene-like heterostructures can induce a ferromagnetic phase characterized by spontaneous axial currents and magnetic fields, with implications for energy stability.

Contribution

It introduces a mechanism for impurity-induced ferromagnetism in graphene-based systems and analyzes the conditions and properties of this magnetic state.

Findings

Ferromagnetic phase appears for impurity charge Z above a critical Z*

Induced magnetic dipole reduces the system's Casimir energy

Spontaneous magnetization occurs above the critical impurity charge Z*

Abstract

The spontaneous self-consistent generation of axial current and corresponding dipole-like magnetic field in a planar electron-positron system similar to graphene and related hetero-structures doped by charged impurity with charge $Z$ is explored. It is shown that this effect takes place for $Z \geq Z^{\ast}$ with $Z^{\ast}$ being a peculiar analogue of the Curie point in ferromagnetics. The properties of induced ferromagnetic state are studied in detail. It is shown also that the arising this way magnetic dipole leads to a significant decrease of the total Casimir (vacuum) energy of the system, which in turn provides its spontaneous generation above the "Curie point" $Z \geq Z^{\ast}$.