Energy shift of collective modes in spin-imbalanced graphene on SiO$_2$ from spin-sensitive linear response theory

TL;DR

This paper investigates how partial spin polarization affects the collective charge and spin excitations in graphene on SiO2, revealing shifts, broadening of plasmons, and an antiresonance in magnetic response, relevant for spintronic applications.

Contribution

It introduces spin-sensitive linear response functions for graphene and predicts how spin polarization influences plasmon modes and magnetic responses.

Findings

Spin polarization causes broadening and shifting of plasmon modes.

An antiresonance appears in the magnetic response function.

Reflectivity of graphene on SiO2 is affected by spin polarization.

Abstract

The growing precision of optical and scattering experiments necessitates a better understanding of the influence of damping onto the collective mode of sheet electrons. As spin-polarized systems are of particular interest for spintronic applications, we here report spin-sensitive linear response functions of graphene, which give access to charge- and spin-density related excitations. We further calculate the reflectivity of graphene on an SiO 2 surface, a setup used in s-wave scanning near field microscopy. Increasing the partial spin-polarization of the graphene charge carriers leads to a significant broadening and shift of the plasmon mode, due to single-particle interband transitions of the minority spin carriers. We also predict an antiresonance in the longitudinal magnetic response function, similar to that of semiconductor heterostructures.