Edge magnetoplasmons in a wide armchair graphene ribbon with a weak superlattice potential: finite frequency gaps and zero group velocity

TL;DR

This paper investigates how a weak superlattice potential affects edge magnetoplasmons in wide graphene ribbons under quantum Hall conditions, revealing finite frequency gaps and zero group velocity regions that influence plasmon dispersion and resonance behavior.

Contribution

It demonstrates the significant impact of a weak superlattice potential on EMPs, including the enlargement of EMP modes and the emergence of frequency gaps and zero group velocity points.

Findings

Superlattice potential enlarges the number of EMPs.

EMP dispersion shows frequency gaps and zero group velocity regions.

Dispersion depends strongly on superlattice period and gate distance.

Abstract

We show strong effects of a weak and smooth, on the magnetic length, superlattice potential upon edge magnetoplasmons (EMPs) at the armchair edge, with a smooth steplike electrostatic lateral confining potential, of a wide graphene channel in the $\nu=2$ quantum Hall effect regime. The superlattice potential leads to essential enlargement of a number of EMPs, descend from two fundamental EMPs in the absence of superlattice. For the wave vector $k_{x}$ within the first Brillouin zone, the EMPs show as the regions of acoustical or quasi-acoustical dispersion, with a finite value of group velocity, so the regions with frequency gaps, where a group velocity is nullified at some $k_{x}$. We obtain that for $k_{x} \to 0$ only for two EMPs the frequency tends to zero as for other EMPs it obtains finite values. Strong dependence of dispersion relations of the EMPs from the period of the superlattice $a_{0}$ and the distance $d$ from a metallic gate is shown; in particular, for typical size of a gap, for characteristic value of the frequency and $k_{x}$ at which the group velocity is reduced to zero. At the frequency that corresponds to zero group velocity of pertinent fundamental EMP branch the response of the system should present a strong resonance.