Mahdi Esmaeilzadeh

Accelerator Physics

PhD
32.06

Publications

  • M Ali M Keshtan · Mahdi Esmaeilzadeh
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    ABSTRACT: Using the Keldysh non-equilibrium Green's function method and applying the Landauer-Büttiker formula, the spin-dependent electron transport properties of a zigzag phosphorene nanoribbon at zero temperature are studied. The depositing of two ferromagnetic strips on the edges of the nanoribbon induces exchange fields with parallel and anti-parallel configurations. An external perpendicular electric field is also applied to manipulate the spin-dependent electron conductance properties. Due to the order of the zigzag phosphorene nanoribbon edge bands near zero Fermi energy, parallel and anti-parallel configurations result in different properties. For anti-parallel configuration, spin filtering only occurs in the presence of a perpendicular electric field, while in the parallel case spin filtering takes place both in the absence and in the presence of an electric field. Although spin filtering properties are invariant against the inversion of the direction of the electric field in a parallel configuration, this inversion changes the spin filtering type for anti-parallel configurations.
    No preview · Article · Dec 2015 · Journal of Physics D Applied Physics
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    ABSTRACT: We study spin-dependent electron transport properties of zigzag silicene nanoribbons in the presence of anti-ferromagnetic exchange field using a nonequilibrium Green's function method. Applying a transverse electric field, spin splitting can take place and the silicene nanoribbon can work as a spin filter. The spin polarization is calculated and it is shown that the spin filtering is perfect and the spin states of electrons are fully coherent. The spin direction of transmitted electrons through the silicene filter can be easily controlled by changing the transverse electric field direction. Using Hubbard model, we take into account the electron-electron interaction and we find that although this interaction causes some changes in the electron conductance, it has no destructive effect on spin filtering properties. The effect of a single vacancy on electron transport is also investigated and it is found that, the vacancy causes to decrease the electron conductance; however, the spin-dependent properties remain the same. The vacancy in the near of the edges of nanoribbon has less destructive effect on electron conductance than that in the middle.
    Full-text · Article · Nov 2015 · Solid State Communications
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    Hamidreza Simchi · Mahdi Esmaeilzadeh · Hossein Maziabadi
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    ABSTRACT: We study a new DNA sequencing method based on quantum interference in the different types of carbon based quantum rings using non-equilibrium Green’s function. We show that the zigzag, graphene, and graphyne quantum rings can be used for DNA sequencing with high sensitivity. The effect of orientation of nucleobases is taken into account and it is shown that the change of orientation has no destructive effect on the sequencing process.
    Full-text · Article · Oct 2015 · Journal of Computational and Theoretical Nanoscience
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    Kh. Shakouri · H. Simchi · M. Esmaeilzadeh · H. Mazidabadi · F. M. Peeters
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    ABSTRACT: Using the tight-binding formalism, we study spin and charge transport through a zigzag silicene ribbon subject to an external electric field Ez. The effect of an exchange field Mz is also taken into account and its consequences on the band structure as well as spin transport are evaluated. We show that the band structure lacks spin inversion symmetry in the presence of intrinsic spin-orbit interaction in combination of Ez and Mz fields. Our quantum transport calculations indicate that for certain energy ranges of the incoming electrons the silicene ribbon can act as a controllable high-efficiency spin polarizer. The polarization maxima occur simultaneously with the van Hove singularities of the local density of states. In this case, the combination of electric and exchange fields is the key to achieving nearly perfect spin polarization, which also leads to the appearance of additional narrow plateaus in the quantum conductance. Moreover, we demonstrate that the output current still remains completely spin-polarized for low-energy carriers even when a few edge vacancies are present.
    Full-text · Article · Jul 2015 · Physical Review B
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    ABSTRACT: Using non-equilibrium Green’s function, we study the spin-dependent electron transport propertiesin a zigzag silicene nanoribbon. To produce and control spin polarization, it is assumed that twoferromagnetic strips are deposited on the both edges of the silicene nanoribbon and an electric field is perpendicularly applied to the nanoribbon plane. The spin polarization is studied for both parallel and anti-parallel configurations of exchange magnetic fields induced by the ferromagnetic strips. We find that complete spin polarization can take place in the presence of perpendicular electric field for anti-parallel configuration and the nanoribbon can work as a perfect spin filter. The spin direction of transmitted electrons can be easily changed from up to down and vice versa by reversing the electric field direction. For parallel configuration, perfect spin filtering can occur even in the absence of electric field. In this case, the spin direction can be changed by changing the electron energy. Finally, we investigate the effects of nonmagnetic Anderson disorder on spin dependent conductance and find that the perfect spin filtering properties of nanoribbon are destroyed by strong disorder, but the nanoribbon retains these properties in the presence of weak disorder.
    Full-text · Article · May 2015 · Journal of Applied Physics
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    ABSTRACT: We investigate the effect of an off-center donor impurity on the electronic properties of a two-dimensional quantum ring with a deformed geometrical structure in the form of an ellipse. It is shown that the dislocation of impurity from the center of elliptical quantum ring opens sizable gaps in the energy spectrum and largely deforms the eigenenergies near the ground state. As a result, the Aharonov–Bohm oscillations are quenched and the persistent electron current decreases intensely. Moreover, we show that the ground state energy exhibits a local extremum when the donor impurity is located on semi-minor (or -major) axis of the elliptic ring. The effects of the eccentricity of elliptical ring on the energy spectra and persistent current are also studied.
    Full-text · Article · Feb 2015 · Physica B Condensed Matter
  • Mohsen Farokhnezhad · Mahdi Esmaeilzadeh · Somayeh Ahmadi

    No preview · Conference Paper · Feb 2015
  • Mohsen Farokhnezhad · Mahdi Esmaeilzadeh · Somayeh Ahmadi

    No preview · Conference Paper · Feb 2015
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    Golshad Kheiri · Mahdi Esmaeilzadeh
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    ABSTRACT: We study the effects of electron beam velocity spread, temperature, and self-fields on dispersion relation and growth rate in a Cherenkov radiation when an axial magnetic field is present. A generalized dispersion relation is derived and shown that in addition to cyclotron, FEL, and beam modes there are two other modes which are induced by thermal velocity of electron beam. For cyclotron mode, the effects of electron beam self-fields on the growth rate are investigated and shown that the growth rate in the presence of self-fields has a maximum value which is considerably greater than the saturation value of growth rate in the absence of self-fields. The optimum value of axial magnetic field at which the maximum growth can take place is determined for different electron beam densities. Then the effects of electron beam velocity spread and temperature on growth rate are studied and it is found that the electron beam temperature causes an increment in growth rate, while the velocity spread of electron beam has an opposite effect.
    Full-text · Article · Feb 2015 · The European Physical Journal D
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    ABSTRACT: It is shown that, for appropriate values of electron energy, the silicene dot can work as a controllable spin polarizer. The spin polarizer can polarize the spin of transmitted electrons from nearly pure down to nearly pure up by changing the strength of an external electric field. Also, for spin polarized incoming electrons, the silicene quantum dot can invert the spin of electrons and can works as a spin inverter or a spin NOT gate. In addition, we investigate the effects of exchange field, induced by ferromagnetic substrate, on electron conductance and show that the silicene quantum dot can act as a nearly perfect spin-filter in the presence of exchange field.
    Full-text · Article · Jan 2015
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    ABSTRACT: The spin-dependent conductance and spin-polarization of a MoS2 quantum dot are studied in presence (absent) of an external electric field perpendicular to the molybdenum plane. It is shown that in absence of the electric field, the deformation of a MoS2 ribbon structure causes spin-splitting in the dot and non-prefect spin filtering is seen. Therefore, the technique could be used for designing spin-dependent devices of MoS2. Also, we show that the device could behave as a prefect spin filter and spin inverter under applying an external electric.
    Full-text · Article · Jan 2015
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    ABSTRACT: We consider a zigzag nanoribbon of MoS2 and study its spin-dependent conductance and spin-polarization in presence (absent) of an external electric field. The field is not only perpendicular to the molybdenum plane (called vertical field Ez) but also to the transport direction of electrons (called transverse field Et). It is shown that, while in the absent of the external electric field, two bands of seven bands are spin split in the valence band but no spin splitting is seen at point . Under applying the electric field we show, the ribbon behaves as a prefect spin up (down) filter if and only if the both components of the electrical field are present. Finally it is shown that, by changing the strength of , the ribbon acts as a spin inverter for fixed values of Ez .
    Full-text · Article · Dec 2014
  • Golshad Kheiri · Mahdi Esmaeilzadeh
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    ABSTRACT: We study the effects of electron beam parameters such as electron beam temperature and Lorentz relativistic factor (or electron energy) on growth rate in a realistic (three-dimensional) helical wiggler free-electron laser with ion-channel guiding. A generalized dispersion relation is derived by considering the interaction between the radiation fields and electron beam when the effects of electron beam self-fields are taken into account. The growth rate is then calculated, and it is found that, for group I orbits, there is an optimum value for electron beam density at which the growth rate goes to its maximum. Also, there is an optimum value for Lorentz relativistic factor. The effect of beam temperature is also investigated, and it is shown that the growth rate decreases considerably as beam temperature increases.
    No preview · Article · Dec 2014 · Physica Scripta
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    ABSTRACT: We study the spin transport and polarization properties of manganese-doped dual-guanine molecules connected to graphene leads using non-equilibrium Green's function method. It is shown that a manganese doped dual-guanine molecule is a biological semiconductor and behaves as a prefect spin filter. We show that this semiconductor can behave as a spin switch when the Rashba spin-orbit interaction is considered. In addition, it is shown that, a large conductance is observed due to the Fano-Kondo-Rashba resonance effect.
    Full-text · Article · Nov 2014
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    Hossein Mazidabadi · Hamidreza Simchi · Mahdi Esmaeilzadeh
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    ABSTRACT: Electronic and magnetic properties of graphene Möbius strips with different widths are studied using density functional theory. It is shown that the multiplicity of the Möbius strip, the cohesive energy, and the band gap energy increase with increasing the width of Möbius strip.We show that the magnetic moment of Möbius strip decreases with increasing the curvature and strain. Then the effects of an external electric field applied in the direction of the Möbius strip axis are studied and it is found that the Möbius strip keeps its metallic surface (edge) states even in the presence of the electric field. For sufficiently high applied electric field, the spin-flipping can take place in the Möbius strip. In addition, in contrast with the graphene nanoribbons, the graphene Möbius strips show half-semiconducting propertieswhen an external electric field is applied.
    Full-text · Article · Sep 2014
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    Hossein Mazidabadi · Hamidreza Simchi · Mahdi Esmaeilzadeh
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    ABSTRACT: Electronic and magnetic properties of graphene Möbius strips with different widths are studied using density functional theory. It is shown that the multiplicity of the Möbius strip, the cohesive energy, and the band gap energy increase with increasing the width of Möbius strip.We show that the magnetic moment of Möbius strip decreases with increasing the curvature and strain. Then the effects of an external electric field applied in the direction of the Möbius strip axis are studied and it is found that the Möbius strip keeps its metallic surface (edge) states even in the presence of the electric field. For sufficiently high applied electric field, the spin-flipping can take place in the Möbius strip. In addition, in contrast with the graphene nanoribbons, the graphene Möbius strips show half-semiconducting propertieswhen an external electric field is applied.
    Full-text · Article · Sep 2014 · Journal of Nanoscience and Nanotechnology
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    Hamidreza Simchi · Mahdi Esmaeilzadeh · Hossein Mazidabadi
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    ABSTRACT: Spin-polarization in double-stranded DNA is studied in the presence of a magnetic field applied along its helix axis using the non-equilibrium Green's function method. The spin-polarization could be tuned by changing the magnetic field. In some special cases, the double-stranded DNA behaved as a perfect spin-filter. Furthermore, the dependency of the spin-polarization on the spin-orbit strength and dephasing strength is studied.
    Full-text · Article · May 2014 · Journal of Applied Physics
  • Leila Eslami · mahdi esmaeilzadeh
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    ABSTRACT: Spin-dependent electron transport in an open double quantum ring, when each ring is made up of four quantum dots and threaded by a magnetic flux, is studied. Two independent and tunable gate voltages are applied to induce Rashba spin-orbit effect in the quantum rings. Using non-equilibrium Green’s function formalism, we study the effects of electron-electron interaction on spin-dependent electron transport and show that although the electron-electron interaction induces an energy gap, it has no considerable effect when the bias voltage is sufficiently high. We also show that the double quantum ring can operate as a spin-filter for both spin up and spin down electrons. The spin-polarization of transmitted electrons can be tuned from �1 (pure spin-down current) to þ1 (pure spin-up current) by changing the magnetic flux and/or the gates voltage. Also, the double quantum ring can act as AND and NOR gates when the system parameters such as Rashba coefficient are properly adjusted.
    No preview · Article · Feb 2014 · Journal of Applied Physics
  • Hamidreza Simchi · Mahdi Esmaeilzadeh · Hossein Mazidabadi
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    ABSTRACT: The spin-dependent electron transport properties of zinc- and manganese-doped adenine molecules connected to zigzag graphene leads are studied in the zero bias regime using the non-equilibrium Green’s function method. The conductance of the adenine molecule increased and became spin-dependent when a zinc or manganese atom was doped into the molecules. The effects of a transverse electric field on the spin-polarization of the transmitted electrons were investigated and the spin-polarization was controlled by changing the transverse electric field. Under the presence of a transverse electric field, both the zinc- and manganese-doped adenine molecules acted as spin-filters. The maximum spin-polarization of the manganese-doped adenine molecule was greater than the molecule doped with zinc.
    No preview · Article · Jan 2014 · Journal of Applied Physics
  • Amiri Mَ Golsorkhtabaramiri M Esmaeilzadeh S Ghofrani F Bijani A Ghorbani L Delavar MA

    No preview · Article · Jan 2014

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