Abstract

We theoretically study current dynamics of graphene nanoribbons subject to DC-AC driven fields. We show that graphene exhibits negative differential conductivity (NDC) at high-harmonics. NDC occurs in the neighborhood where a constant electric field is equal to amplitude of ac field. We also observe NDC at both even and odd harmonics and at wave mixing of two commensurate frequencies. The even harmonics are more pronounced than the odd harmonics. A possible use of the present method for generating terahertz frequencies at even harmonics in graphene is suggested.

Highlights

  • Graphene has attracted much attention since its discovery in 2004 by Geim and his team [1]

  • We theoretically study current dynamics of graphene nanoribbons subject to DC-AC driven fields

  • We show that graphene exhibits negative differential conductivity (NDC) at high-harmonics

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Summary

Introduction

Graphene has attracted much attention since its discovery in 2004 by Geim and his team [1]. Various attempts have been made to introduce 2D graphene sheet, for the purpose of overcoming some of these challenges, into a 1D + quantization This phenomenon results into graphene nanoribbon (GNR) which is assumed as an unrolled single-wall carbon nanotube (SWCNT). We employ Boltzmann transport equation based on relaxation time approximation to study negative differential conductivity (NDC) in GNRs. In conventional semiconductor devices including semiconductor superlattices, an NDC behavior is known to offer great potential for high frequency applications as Bloch oscillators, frequency multipliers, and fast switching devices. In conventional semiconductor devices including semiconductor superlattices, an NDC behavior is known to offer great potential for high frequency applications as Bloch oscillators, frequency multipliers, and fast switching devices For this reason, the NDC effect has been greatly explored and discussed in several graphene nanostructures, in [7].

The Theory
Armchair and Zigzag Nanoribbon Band Structures
Sheet Current Density
Monoharmonics
Pure DC Limit
Biharmonics
Discussion and Conclusions
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