Plasmons in spin polarized graphene: a new way to measure spin polarization

TL;DR

This paper investigates how spin polarization affects plasmons in graphene, proposing a method to measure spin polarization by analyzing the spin-dependent critical wave vector where plasmons decay into electron-hole pairs.

Contribution

The study derives explicit dispersion relations for plasmons in spin polarized graphene and reveals a novel, spin-dependent critical wave vector useful for experimental spin polarization measurement.

Findings

Critical wave vector depends strongly on spin polarization

Plasmon-electron-hole coupling varies with spin polarization

Method robust against disorder effects

Abstract

We study the collective charge excitations (plasmons) in spin polarized graphene, and derive explicit expressions for their dispersion in the undamped regime. From this, we are able to calculate the critical wave vector beyond which the plasmon enters the electron-hole continuum, its quality factor decreasing sharply. We find that the value of the critical wave vector is strongly spin polarization-dependent, in a way that has no analog in ordinary two-dimensional electron gases. The origin of this effect is in the coupling between the plasmon and the inter-band electron-hole pairs of the minority spin carriers. We show that the effect is robust with respect to the inclusion of disorder and we suggest that it can be exploited to experimentally determine the spin polarization of graphene.