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Acoustomagnetoelectric Effect (AME) in Graphene Nanoribbon (GNR) in the presence of an external electric and magnetic fields was studied using the Boltzmann kinetic equation. On open circuit, the Surface Acoustomagnetoelectric field ( E SAM E ) in GNR was obtained in the region ql >> 1, for energy dispersion ε(p) near the Fermi level. The dependence of E SAM E on the magnetic field strength (η), the sub-band index (p i ), and the width (N ) of GNR were analysed numerically. For E SAM E versus η, a non-linear graph was obtained. From the graph, at low magnetic field strength (η < 0.62), the obtained graph qualitatively agreed with that experimentally observed in graphite. However, at high magnetic field strength (η > 0.62), the E SAM E falls rapidly to a minimum value. We observed that in GNR, the maximum E SAM E was obtained at magnetic field H = 3.2Am −1 . The graphs obtained were modulated by varying the sub-band index p i with an inversion observed

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We present a theoretical study of acoustic phonons amplification in Carbon Nanotubes (CNT). The phenomenon is via Cerenkov emission (CE) of acoustic phonons using intraband transitions proposed by Mensah et. al., [1] in Semiconductor Superlattices (SSL) and confirmed in [2]. From this, an asymmetric graph of Γ CN T on V d Vs and Ωτ were obtained where amplification (Γ CN T amp ) >> absorption (Γ CN T abs ). The ratio, |Γ CN T amp | |Γ CN T abs | ≈ 3.5, at V d = 1.02V s , ω q = 3.0 THz and T = 85 K for scattering angle θ > 0 . A threshold field at which Γ CN T abs switches over to Γ CN Tamp was calculated to be E dc z = 6.2 × 10 3 V/m. This field is far less than that deduced using Bloch-Type Oscillation (BTO) [3] which is E dc BT O = 3.0 × 10 5 V/m. The obtained Γ CN T amp would enable the use of CNT for the production of SASER.

Generation and propagation of ultrasonic waves in single layer Graphene Nanoribbon is studied using semi-classical approach. When piezoelectric Graphene Nanoribbon (GNR) is exposed to time varying light beam, ultrasonic waves are produced which propagate in the medium. At low frequencies, we observed oscillations of the ultrasonic observables, velocity change and attenuation which are characteristics of massless Dirac fermions in graphene. Exploiting this oscillatory behavior, we estimate graphene's electronic mobility to be around 5 2 10 cm V s . Propagating ultrasonic waves can be amplified, depending on the electric field amplitude. Specifically, amplification occurs when drift velocity exceeds sound velocity. This scheme can be employed for efficient ultrasonic amplifier device operation.

We study theoretically the electron transport properties in achiral carbon nanotubes under the influence of an external electric field <i>E(t)</i> using Boltzmann’s transport equation to derive the current-density. A negative differential conductivity (NDC) is predicted in quasi-static approximation <i>i.e.</i>, <i>ωτ</i> << 1, similar to that observed in superlattice. However, a strong enhancement in the current density intensity is observed in NDC of the achiral carbon nanotubes. This is observed at where the constant electric field E₀ is equal to the amplitude of the AC electric field E₁. The peak of the NDC intensity occurs at very weaker fields than that of superlattice under the same conditions. The peak intensity decreases and shifts to right with the increase in the amplitude of the ac field. This mechanism suppresses the domain formation and therefore could be used in terahertz frequency generation

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 &lt; 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.