Dielectric properties of graphene on transition metal dichalcogenide substrate

TL;DR

This paper investigates how substrate interactions and magnetic impurities influence the dielectric properties and plasmon behavior of graphene on transition metal dichalcogenides, revealing tunable collective modes and unique dispersion characteristics.

Contribution

It provides an analytical expression for the dielectric function of graphene on TMDCs, highlighting the impact of spin-orbit couplings and magnetic interactions on plasmon dispersion and tunability.

Findings

Only one charge plasmon mode observed.

Plasmon dispersion follows q^{2/3} behavior.

Plasmon frequency tunable via chemical potential.

Abstract

The tunability of the dielectric properties induced by the substrate driven interactions (SDI) and the exchange field (M) due to the ferro-magnetic impurities in graphene monolayer on transition metal dichalcogenide (TMDC) (viz., XY2 , X = Mo, W; Y = S, Se) around K and K prime points is reported here. The cavalcade of interactions involve sub-lattice-resolved, strongly enhanced intrinsic spin-orbit couplings(SOC), the extrinsic Rashba spin-orbit coupling (RSOC), and the orbital gap related to the transfer of the electronic charge from graphene to XY2. The RSOC allows for external tuning of the band gap in graphene and connects the nearest neighbors with spin-flip. We obtain the usual gapped bands with an effective, RSOC-dependent Zeeman field due to the interplay of SDI. Using these bands we obtain the closed analytical expression of the dielectric function in the finite doping case. The zero of the dielectric function corresponds to the collective mode. Upon including the full dispersion of graphene on TMDC, we find that there is in fact only one collective mode and it corresponds to charge plasmons. The dispersion of the latter yields the q^2/3 behavior and not the well known q^1/2 behavior. We also find that the plasmon frequency could be changed by the tuning of the chemical potential.