High frequency conductivity in carbon nanotubes

Abstract

We report on theoretical analysis of high frequency conductivity in carbon nanotubes. Using the kinetic equation with constant relaxation time, an analytical expression for the complex conductivity is obtained. The real part of the complex conductivity is initially negative at zero frequency and become more negative with increasing frequency, until it reaches a resonance minimum at ω ∼ ωB for metallic zigzag CNs and ω < ωB for armchair CNs. This resonance enhancement is indicative for terahertz gain without the formation of current instabilities induced by negative dc conductivity. We noted that due to the high density of states of conduction electrons in metallic zigzag carbon nanotubes and the specific dispersion law inherent in hexagonal crystalline structure result in a uniquely high frequency conductivity than the corresponding values for metallic armchair carbon nanotubes. We suggest that this phenomenon can be used to suppress current instabilities that are normally associated with a negative dc differential conductivity.

Hypersound Absorption of Acoustic Phonons in a Degenerate Carbon Nanotube

“…where Ω = eaE (E is the electric field, r the radius of the CNT, and a = 3b/2h). The V d is solved from the Boltzmann kinetic equation in the τapproximation [21,22,23]. The justification for the τ -approximation can be found in [17].…”

sd-Exchange electron spin resonance in a ferromagnetic metal

“…A number of new methods, including those with the use of "new" materials such as graphene [1,2] and carbon nanotubes [3], were proposed. One of the promising directions is the use of spin injection in magnetic transitions [4][5][6][7] that results in the inverse population of spin energy subbands.…”

Stark-cyclotron Resonance in an Array of Carbon Nanotubes

“…The indices (n, m) determine the diameter and the chiral angle of the CN s. As n and m vary, the conduction ranges from metallic to semiconducting [11], with an inverse diameter dependent band gap of ≤ 1eV [11]. Electron transport properties in CNs have been the subject of intense research [10,11,12,13,14,15,16,17,18]. More recently, electronic transport in an array of CNs is the subject of many theoretical papers [19,20,21,22,23,24,25,26,27,28].…”