RPA Plasmons in Graphene Nanoribbons: Influence of a VO2 Substrate

Abstract

We study the effect of the phase-change material VO2 on plasmons in metallic arm-chair graphene nanoribbons (AGNRs) within the random-phase approximation (RPA) for intra- and inter-band transitions. We assess the influence of temperature as a knob for the transition from the insulating to the metallic phase of VO2 on localized and propagating plasmon modes. We show that AGNRs support localized and propagating plasmon modes and contrast them in the presence and absence of VO2 for intra-band (SB) transitions while neglecting the influence of a substrate-induced band gap. The presence of this gap results in propagating plasmon modes in two-band (TB) transitions. In addition, there is a critical band gap below and above which propagating modes have a linear negative or positive velocity. Increasing the band gap shifts the propagating and localized modes to higher frequencies. In addition, we show how the normalized Fermi velocity increases plasmon modes frequency.

Transverse Magnetic Surface Plasmons in Graphene Nanoribbon Qubits: The Influence of a VO2 Substrate

“…In Equation ( 1 ), denotes the conductivity of the quantum material given by [ 44 ]: with e and being the electron charge and polarization function, respectively [ 45 ]. In the absence of many-body effects, such as Coulomb interaction or exchange effects, this quantity for AGNRs and SB transitions is given by [ 40 ]: and for TB transitions, it is given by: where , , and are the dimensionless wave vector, frequency, and renormalized Fermi velocity, respectively [ 46 ]. Note that , where indicates the energy gap induced by the substrate on the polarization function of AGNRs.…”

“…In this paper, we study the influence of a VO 2 substrate phase change with temperature on the TM surface plasmon modes of arm-chair graphene nanoribbons as qubits for single-band (SB) and two-band (TB) transitions, which are also known as intra-band and inter-band transitions. Note that, in our previous paper, we studied the influence of VO 2 on plasmon modes in AGNRs [ 40 ]. It is worth pointing out that plasmon modes are longitudinal electromagnetic fields propagating inside AGNRs, while surface plasmon modes are TM or TE evanescent electromagnetic fields propagating at the interface of AGNRs with the surrounding media.…”