Negative dynamic conductivity of a current driven array of graphene nanoribbons

TL;DR

This paper demonstrates that a current-driven array of graphene nanoribbons can exhibit negative dynamic conductivity, leading to electromagnetic wave amplification, with potential applications in terahertz emission and surface acoustic wave devices.

Contribution

It provides a theoretical analysis of negative dynamic conductivity in graphene nanoribbons under strong electric fields, linking it to wave amplification and experimental contexts.

Findings

Real part of conductivity can become negative under certain conditions.

Negative absorption coefficient indicates wave amplification.

Potential for graphene-based terahertz emitters.

Abstract

We consider a periodic array of graphene nanoribbons under the action of a strong dc electric field $E_0$ and an external electromagnetic excitation with the frequency $\omega$ and the lateral wave vector $q$. Solving the quasi-classical Boltzmann kinetic equation and calculating the surface dynamic conductivity $\sigma_{2D}(q,\omega,E_0)$ and the absorption coefficient of such a system we show that the real part of the conductivity and the absorption coefficient may become negative under certain conditions. Physically this corresponds to the amplification of the electromagnetic waves at the expense of the energy of the direct current source. The results are discussed in connection with experiments on the surface acoustic waves and on the Smith-Purcell-type graphene-based terahertz emitter.