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General Scattering Mechanism and Transport in Graphene

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Graphene 2013年第1期2卷 49-54页

作者： Musah Rabiu samuel y. mensah Sulemana S. Abukari Center for Laser and Fiber Optics Physics Department University of Cape Coast Cape Coast Ghana University.for Development Studies Faculty of Applied Science Department of Applied Physics Navrongo Ghana

Using quasi time dependent semiclassical transport theory. within relaxation time approximation, we obtained coupled electronic current equations in the presence of time vary.ng field, and based on general scattering mechanism,. In the vicinity.of Dirac points, we find that a characteristic exponent?corresponds to acoustic phonon scattering,?long range Coulomb scattering mechanism and?is short range (delta or contact potential) scattering in which the conductivity.is constant of temperature. The?case is the ballistic regime. In the low energy.dy.amics of Dirac electrons in graphene, the effect of the time dependent electric field is to alter just the electron charge by.making electronic conductivity.nonlinear. The effect of constant magnetic field at finite temperature is also considered.

关键词： Boltzmann Transport Equation Relaxation Time Approximation Graphene Energy Spectrum Electronic Conductivity Scattering

Anomalous Viscosity.of Vortex Hall States in Graphene

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Journal of Applied Mathematics and Phy.ics 2015年第12期3卷 1654-1661页

作者： Rabiu Musah samuel y. mensah Ibrahim y. Seini Sulemana S. Abukari Department of Applied Mathematics Faculty of Mathematical Sciences University for Development Studies Navrongo Campus Upper East Ghana Department of Phy.ics Laser and Fiber Optics Center University of Cape Coast Cape Coast Ghana

We study.temperature effect on anomalous viscosity.of Graphene Hall fluid within quantum many.vortex hy.rody.amics. The commonly.observed filling fraction, in the range is considered. An expression for anomalous viscosity.dependent on a geometric parameter-Hall expansion coefficient is obtained at finite temperatures. It arises from strained induced pseudo-magnetic field in addition to an anomalous term in vortex velocity. which is responsible for renormalization of vortex-vortex interactions. We observed that both terms greatly.modify.the anomalous viscosity.as well as an enhancement of weakly.observed v fractions. Finite values of the expansion coefficient produce constant and infinite viscosities at vary.ng temperatures. The infinities are identified as energy.gaps and suggest temperatures at which new stable quantum hall filling fractions could be seen. This phenomenon is used to estimate energy.gaps of already.measured fractional Quantum Hall States in Graphene.

关键词： Euler Hy.rody.amics Quantum Hall Fluid Vortex Dy.amics Fractional Quantum Hall Effect Anomalous Viscosity Hall Expansion Coefficient

Appearance of Negative Differential Conductivity.in Graphene Nanoribbons at High-Harmonics

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Graphene 2013年第2期2卷 61-65页

作者： Musah Rabiu samuel y. mensah Sulemana S. Abukari Department of Applied Phy.ics University for Development Studies Navrongo Ghana Phy.ics Department Center for Laser and Fiber Optics University of Cape Coast Cape Coast Ghana

We theoretically.study.current dy.amics 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.

关键词： Graphene Nanoribbon Energy Spectrum Electronic Conductivity Terahertz Negative Differential Conductivity

Direct Current Generation in Carbon Nanotubes by.Terahertz Field

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World Journal of Condensed Matter Phy.ics 2016年第1期6卷 56-62页

作者： Sulemana S. Abukari Frederick Sam samuel y. mensah Natalia G. mensah Rabiu Musah Anthony.Twum Patrick M. Amoah Alfred Owusu Department of Phy.ics Laser and Fibre Optics Centre University of Cape Coast Cape Coast Ghana Department of Mathematics University of Cape Coast Cape Coast Ghana Department of Applied Phy.ics University for Development Studies Navorongo Ghana

We report on a theoretical investigation of a direct current generation in carbon nanotubes (CNTs) that are stimulated axially.by.terahertz (THz) field. We consider the kinetic approach based on the semiclassical Boltzmann’s transport equation with constant relaxation time approximation, together with the energy.spectrum of an electron in the tight-binding approximation. Our results indicate that for strong THz-fields, there is simultaneous generation of DC current in the axial and circumferential directions of the CNTs, even at room temperature. We found that a THz-field can induce a negative conductivity.in the CNTs that leads to the THz field induced DC current. For vary.ng amplitude of the THz-field, the current density.decreases rapidly.and modulates around zero with interval of negative conductivity. The interval decreases with increasing the amplitude of the THz-field. We show that the THz-field can cause fast switching from a zero DC current to a finite DC current due to the quasi-ballistic transport, and that electron scattering is a necessary.condition for switching.

关键词： Carbon Nanotubes Terahertz Fields DC Voltage Generation Negative Conductivity Electron Scattering Ballistic Transport

Induced Hall-Like Current by.Acoustic Phonons in Semiconductor Fluorinated Carbon Nanotube

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World Journal of Condensed Matter Phy.ics 2020年第2期10卷 71-87页

作者： Daniel Saky.-Arthur samuel y. mensah Kofi W. Adu Kwadwo A. Dompreh Ray.ond Edziah Natalia G. mensah Cy.thia Jebuni-Adanu Department of Phy.ics College of Agriculture and Natural Sciences U.C.C Ghana Department of Mathematics College of Agriculture and Natural Sciences U.C.C Ghana Department of Phy.ics Pennsylvania State University-Altoona College Altoona Pennsylvania USA Material Research Institute Pennsylvania State University University Park Pennsylvania USA St. Francis College of Education Hohoe Volta Region Ghana

We show that Hall-like current can be induced by.acoustic phonons in a nondegenerate, semiconductor fluorine-doped single-walled carbon nanotube (FSWCNT) using a tractable analy.ical approach in the hy.ersound regime ?(q is the modulus of the acoustic wavevector and is the electron mean free path). We observed a strong dependence of the Hall-like current on the magnetic field, H, the acoustic wave frequency. , the temperature, T, the overlapping integral, , and the acoustic wavenumber, q. Qualitatively. the Hall-like current exists even if the relaxation time does not depend on the carrier energy.but has a strong spatial dispersion, and gives different results compared to that obtained in bulk semiconductors. For and , the Hall-like current is in the absence of an electric field and in the presence of an electric field at 300 K. Similarly. the surface electric field due to the Hall-like current is in the absence of an external electric field. In the presence of an external electric field, and for at 300 K. q and can be used to tune the Hall-like current and of the FSWCNT. This offers the potential for room temperature application as an acoustic switch or transistor, as well as a material for ultrasound current source density.imaging (UCSDI) and AE hy.rophone device in biomedical engineering.

关键词： Carbon Nanotube Fluorinated Hall-Like Current Cy.lotron

Generation and Propagation of Ultrasonic Waves in Piezoelectric Graphene Nanoribbon

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Open Journal of Acoustics 2013年第3期3卷 38-42页

作者： Musah Rabiu samuel y. mensah Sulemana S. Abukari Matthew Amekpewu Baah Sefa-Ntiri Anthony.Twum University.for Development Studies Faculty of Applied Science Department of Applied Physics Navrongo Ghana University.of Cape Coast Center for Laser and Fiber Optics Physics Department Cape Coast Ghana

Generation and propagation of ultrasonic waves in single lay.r Graphene Nanoribbon is studied using semi-classical approach. When piezoelectric Graphene Nanoribbon (GNR) is exposed to time vary.ng 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 . 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 employ.d for efficient ultrasonic amplifier device operation.

关键词： Current Density Negative Differential Conductivity Commensurable Frequencies

High-Frequency.Electric Field Induced Nonlinear Electron Transport in Chiral Carbon Nanotubes

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World Journal of Condensed Matter Phy.ics 2015年第4期5卷 294-300页

作者： Sulemana S. Abukari samuel y. mensah Musah Rabiu Kofi W. Adu Natalia G. mensah Anthony.Twum Alfred Owusu Kwadwo A. Dompreh Patrick mensah-Amoah Matthew Amekpewu Department of Phy.ics Laser and Fibre Optics Centre University of Cape Coast Cape Coast Ghana Department of Applied Phy.ics University for Development Studies Navorongo Ghana Department of Phy.ics The Pennsylvania State University-Altoona Altoona USA Materials Research Institute The Pennsylvania State University University Park USA Department of Mathematics University of Cape Coast Cape Coast Ghana

We investigate theoretically.the high frequency.complex conductivity.in carbon nanotubes that are stimulated axially.by.a strong inhomogeneous electric field of the form E(t)=E0+E1cos(ωt). Using the kinetic approach based on Boltzmann’s transport equation with constant relaxation time approximation and the energy.spectrum of the electron in the tight-binding approximation, together with Bhatnagar-Gross-Krook collision integral, we predict high-frequency.nonlinear effects along the axial and the circumferential directions of the carbon nanotubes that may.be useful for the generation of high frequency.radiation in the carbon nanotubes.

关键词： Carbon Nanotubes High Frequency Electric Field Electric Current Density Complex Conductivity

Domain Suppression in the Negative Differential Conductivity.Region of Carbon Nanotubes by.Applied AC Electric Field

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World Journal of Condensed Matter Phy.ics 2012年第4期2卷 274-277页

作者： Sulemana S. Abukari samuel y. mensah Kofi W. Adu Natalia G. mensah Kwadwo A. Dompreh Anthony.Twum Chales L. y. Amuah Matthew Amekpewu Musah Rabiu Department of Applied Phy.ics University for Development Studies Navorongo Ghana Department of Phy.ics Laser and Fibre Optics Centre University of Cape Coast Cape Coast Ghana Department of Phy.ics The Pennsylvania State University Altoona USA Materials Research Institute The Pennsylvania State University University Park USA National Centre for Mathematical Sciences Ghana Atomic Energy Commission Accra Ghana Department of Mathematics University of Cape Coast Cape Coast Ghana

We study.theoretically.the electron transport properties in achiral carbon nanotubes under the influence of an external electric field E(t) using Boltzmann’s transport equation to derive the current-density. A negative differential conductivity.(NDC) is predicted in quasi-static approximation i.e., ωτ 0 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.

关键词： Carbon Nanotubes Negative Differential Conductivity and Generation of Terahertz Radiation

External Electric Field Effect on Electrons Transport in Carbon Nanotubes

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World Journal of Condensed Matter Phy.ics 2013年第4期3卷 169-172页

作者： Sulemana S. Abukari samuel y. mensah Musah Rabiu Kofi W. Adu Natalia G. mensah Kwadwo A. Dompreh Anthony.Twum Matthew Amekpewu Department of Applied Phy.ics University for Development Studies Navorongo Ghana Department of Mathematics University of Cape Coast Cape Coast Ghana Department of Phy.ics Laser and Fibre Optics Centre University of Cape Coast Cape Coast Ghana Department of Phy.ics The Pennsylvania State University Altoona USA Materials Research Institute The Pennsylvania State University University Park USA

We consider a simple model of carbon nanotubes (CNTs) subject to external electric field E(t). Using a tight-binding approximation for the description of energy.bands of CNTs, together with the standard Boltzmann transport equation and constant relaxation time, we predict the effect of self-induced transparency.and absolute negative conductivity. The predicted effects may.be useful in diagnostics of carbon nanotubes as well as in the amplification and efficiency.conversion of electromagnetic signals.

关键词： Carbon Nanotubes Electric Field Electric Current Density Negative Differential Conductivity