Zero mode dependence on the hole structure of antidot graphene lattices

Conference Paper
M. Nabavi , H. Cheraghchi
Annual Physics Conference of Iran, Urmia University, Urmia - , , - January, 2011
Publication year: 2011

Transport gap and Electronic transport through bilayer graphene nanoribbin with the zigzag edges

Conference Paper
V. Derakhshan , H. Cheraghchi , S. A. Ketabi
The 10 th conference on Condensed Matter , Shiraz University, Shiraz, Iran - January, 2011
Publication year: 2011

The effect of unit cell geometry on the stability and band structure of graphene antidot lattices

Conference Paper
M. Nabavi , H. Cheraghchi
Annual Physics Conference of Iran, Urmia University, Urmia - January, 2011
Publication year: 2011

Stability and magnetization of triangular graphene quantum dot with zigzag edges

Conference Paper
Z. Akbarinejad , H. Cheraghchi
Annual Physics Conference of Iran, Urmia University, Urmia - January, 2011
Publication year: 2011

Spin polarization and magnetoresistance through a ferromagnetic barrier in bilayer graphene

ISI Paper
H. Cheraghchi , F. Adinehvand
Accepted in Journal of Physics: Condensed Matter - December, 2011
Publication year: 2011

Abstract

We study spin dependent transport through a magnetic bilayer graphene nanojunction configured as a two-dimensional normal/ferromagnetic/normal structure where the gate voltage is applied on the layers of ferromagnetic graphene. Based on the four-band Hamiltonian, conductance is calculated by using the Landauer–Buttiker formula at zero temperature. For a parallel configuration of the ferromagnetic layers of bilayer graphene, the energy band structure is metallic and spin polarization reaches its maximum value close to the resonant states, while for an antiparallel configuration the nanojunction behaves as a semiconductor and there is no spin filtering. As a result, a huge magnetoresistance is achievable by altering the configurations of ferromagnetic graphene around the band gap.

Nonlinear transport through ultra-narrow zigzag graphene nanoribbons: non-equilibrium charge and bond currents

ISI Paper
H. Cheraghchi
Physica. Scripta. - , 81, 015702 - January, 2011
Publication year: 2011

Abstract

The electronic nonlinear transport through ultra-narrow graphene nanoribbons (sub-10 nm) was studied. A stable region of negative differential resistance (NDR) appears in the I–V characteristic curve of odd zigzag graphene nanoribbons (ZGNRs) at both positive and negative polarity. This NDR originates from a transport gap induced by a selection rule that blocks the electron transition between disconnected energy bands of ZGNR. Based on this transition rule, the on/off ratio of the current increases exponentially with ribbon length up to 105. In addition, charging effects and the spatial distribution of bond currents were studied by using the non-equilibrium Green’s function formalism in the presence of electron–electron interaction at a mean-field level. We also performed an ab initio density functional theory calculation of the transmission through a passivated graphene nanoribbon to demo

Metallic phase of disordered graphene superlattices with long-range correlations

ISI Paper
H. Cheraghchi , A. A. Irani , S. M. Fazeli , R. Asgari
Physical Review. B. - , 83, 235430 - January, 2011
Publication year: 2011

Abstract:

Using the transfer matrix method, we study the conductance of the chiral particles through a monolayer graphene superlattice with long-range correlated disorder distributed on the potential of the barriers. Even though the transmission of the particles through graphene superlattice with white noise potentials is suppressed, the transmission is revived in a wide range of angles when the potential heights are long-range correlated with a power spectrum S(k) ∼ 1/kβ . As a result, the conductance increases with increasing the correlation exponent values gives rise a metallic phase. We obtain a phase transition diagram in which a critical correlation exponent depends strongly on disorder strength and slightly on the energy of the incident particles. The phase transition, on the other hand, appears in all ranges of the energy from propagating to evanescent mode regimes

Magnetization and stability of triangular graphene quantum dots with hydrogen edged saturation in the presence and absence of Fluorine impurity

Conference Paper
Z. Akbarinejad , H. Cheraghchi
Annual Physics Conference of Iran, Urmia University, Urmia - January, 2011
Publication year: 2011

Investigation of energy gap in bilayer graphnene nanoribbon with the zigzag edges

Conference Paper
V. Derakhshan , H. Cheraghchi , S. A. Ketabi
The 10 th conference on Condensed Matter , Shiraz University, Shiraz, Iran - January, 2011
Publication year: 2011

Generation of energy gap in the graphene antidot lattices

Conference Paper
M. Nabavi , H. Cheraghchi
Annual Physics Conference of Iran, Urmia University, Urmia - , , - January, 2011
Publication year: 2011

Considering the effect of different arrangements of pentagons on density of states of capped carbon nanotubes

ISI Paper
S. Khazaei , M. Khazaei , H. Cheraghchi , V. Daadmehr , Y. Kawazoe
Physica B. - , 406, 3885 - January, 2011
Publication year: 2011

Abstract

We have used a non-equilibrium surface Green’s function matching formalism combined with a tight-binding Hamiltonian to consider the effect of different arrangements of pentagon rings on localization of density of states at the tip regions of semi-infinite capped carbon nanotubes. The transfer matrixes are obtained by an iterative procedure. The results demonstrate that the positions of the peaks near Fermi energy are remarkably affected by the relative locations of pentagons. It is observed that in thin nanotubes, carbon atoms belonging two neighboring pentagon rings have significant contribution in the localized states near fermi energy. From our calculations, it turns out that the metallic or semiconducting behavior of capped nanotubes in the tip regions depends on the metallic or semiconducting nature of their nanotube stems.

 

Transport through Graphene Nanoribbons and Disordered Graphene Superlattice

Conference Paper
H. Cheraghchi
Workshop on Graphene and Topological Insulators, School of Physics - Invited Speaker - September, 2010
Publication year: 2010

Spin polarization in bilayer graphene located in the proximity of magnetic insulator

Conference Paper
F. Adinehvand , H. Cheraghchi
The 17th spring conference of physics, Institute for Research in Fundamental Sciences (IPM), Tehran - January, 2010
Publication year: 2010

Resonant states in conductance of graphene superlattice with correlated disorder on potentials

Conference Paper
A. A. Irani , H. Cheraghchi , S. M. Fazeli
Annual Physics Conference of Iran, Bu-Ali Sina University, Hamedan - January, 2010
Publication year: 2010

Nonlinear Electronic Transport through Zigzag Graphene Nanoribbons

Conference Paper
H. Cheraghchi , H. Esmailzade
Spring college on computational nanoscience, ICTP, Trieste, Italy. - May, 2010
Publication year: 2010

Nonlinear electronic transport through zigzag graphene nanoribbon with asymmetric effects

Conference Paper
H. Esmailzade , H. Cheraghchi
The 16th Gava-Zang meeting on condensed matter physics, Institute for advanced studies in basic science, Zanjan, Iran - January, 2010
Publication year: 2010

Metal-insulator transition in the presence of long-range correlated disorder

Conference Paper
A. A. Irani , H. Cheraghchi , S. M. Fazeli
The 16th Gava-Zang meeting on condensed matter physics, Institute for advanced studies in basic science, Zanjan, Iran - January, 2010
Publication year: 2010

Localization-delocalization transition through graphene superlattice with long-range correlated disorder on potential barriers

Conference Paper
H. Cheraghchi , A. A. Irani , S. M. Fazeli
Advanced workshop on Anderson localization, nonlinearity and turbulence: a cross-fertilization”, ICTP, Trieste, Italy. - May, 2010
Publication year: 2010

Gate-Induced Switch of Even Zigzag Graphene Naoribbons and its charging effects

ISI Paper
H. Cheraghchi , H. Esmailzade
Nanotechnology - , 21, 205306 - January, 2010
Publication year: 2010

Abstract

Using the non-equilibrium Green’s function formalism, we investigate nonlinear transport and charging effects of gated graphene nanoribbons (GNRs) with an even number of zigzag chains. We find a negative differential resistance (NDR) over a wide range of gate voltages with an on/off ratio ~ 106 for narrow enough ribbons. This NDR originates from the parity selection rule and also prohibition of transport between discontinuous energy bands. Since the external field is well screened close to the contacts, the NDR is robust against the electrostatic potential. However, for voltages higher than the NDR threshold, due to charge transfer through the edges of the zigzag GNR (ZGNR), screening is reduced such that the external potential can penetrate inside the ribbon giving rise to smaller values of off-current. Furthermore, the on/off ratio of the current depends on the aspect ratio of the length/width and also edge impurity. Moreover, the on/off ratio displays a power law behavior as a function of ribbon length.

Electronic transport through bilayer superlattice graphene

Conference Paper
F. Adinehvand , H. Cheraghchi
The 16th Gava-Zang meeting on condensed matter physics, Institute for advanced studies in basic science, Zanjan, Iran - January, 2010
Publication year: 2010

Conductance of Dirac quasi-particles through bilayer graphene superlattice

Conference Paper
F. Adinehvand , H. Cheraghchi
Annual Physics Conference of Iran, Bu-Ali Sina University, Hamedan - January, 2010
Publication year: 2010

Statistical Properties and conductance of rough graphene sheets

Conference Paper
A. Habibi , H. Cheraghchi
Annual Physics Conference of Iran, Isfahan University of Technology - August, 2009
Publication year: 2009

Graphene sheets as a direction and energy of electronic filter

Conference Paper
A. H. Irani , H. Cheraghchi
The 9 th Condensed Matter Conference , Chamran University, Ahwaz, Iran - February, 2009
Publication year: 2009

Electronic Transport through Disordered Superlattice Graphene

Conference Paper
A. A. Irani , H. Cheraghchi , S. M. Fazeli
The first National Conference on Role of Science in Nanotechnology, Imam Hossein University, Iran - December, 2009
Publication year: 2009

Electronic Transport through Armchair Graphene Nanoribbons

Conference Paper
H. Esmailzade , H. Cheraghchi
The 9 th Condensed Matter Conference , Chamran University, Ahwaz, Iran - February, 2009
Publication year: 2009

Electronic Switch made by Even Graphene Nanoribbons

Conference Paper
H. Esmailzade , H. Cheraghchi
The 15th Gava-Zang meeting on condensed matter physics, Institue for advanced studies in basic science, Zanjan, Iran - May, 2009
Publication year: 2009

Edge Disorder Effects on Spectrum of Conduction Modes in Graphene Nanoribbons

Conference Paper
S. Hosseini , H. Cheraghchi
Annual Physics Conference of Iran, Isfahan University of Technology - August, 2009
Publication year: 2009

Conductance through Superlattice Graphene with Disorder Potential Barriers

Conference Paper
A. A. Irani , H. Cheraghchi , S. M. Fazeli
The first National Conference on Role of Science in Nanotechnology, Imam Hossein University, Iran - January, 2009
Publication year: 2009

Calculating the density of states for carbon nanotubes with different tip geometries using Green's function approach

Conference Paper
S. Khazaei , M. Khazaei , V. Daadmehr , H. Cheraghchi
Annual Physics Conference of Iran, Isfahan University of Technology - August, 2009
Publication year: 2009

Anderson Localization in the Square and Cubic Lattices

Conference Paper
A. Habibi , H. Cheraghchi
The 9 th Condensed Matter Conference , Chamran University, Ahwaz, Iran - February, 2009
Publication year: 2009

Anderson Localization in Graphene Sheets

Conference Paper
S. Hosseini , H. Cheraghchi , A. Habibi
The 9 th Condensed Matter Conference , Chamran University, Ahwaz, Iran - February, 2009
Publication year: 2009

Negative differential resistance in molecular junctions: application to graphene ribbon junctions

ISI Paper
H. Cheraghchi , K. Esfarjani
Physical Review. B. - , 78, 085123 - January, 2008
Publication year: 2008

Abstract:

Using self-consistent calculations based on nonequilibrium Green’s function formalism, the origin of negative differential resistance (NDR) in molecular junctions and quantum wires is investigated. Coupling of the molecule to electrodes becomes asymmetric at high bias due to asymmetry between its highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) levels. This causes appearance of an asymmetric potential profile due to a depletion of charge and reduction of screening near the source electrode. With increasing bias, this sharp potential drop leads to an enhanced localization of the HOMO and LUMO states in different parts of the system. The reduction in overlap, caused by localization, results in a significant reduction in the transmission coefficient and current with increasing bias. An atomic chain connected to two graphene ribbons was investigated to illustrate these effects. For a chain substituting a molecule, an even-odd effect is also observed in the NDR characteristics.

Negative Differential Resistance in Graphene Nanoribbon Junctions

Conference Paper
H. Cheraghchi , K. Esfarjani
National Meeting of strongly Correlated Systems, Sharif University of Technology, Tehran - December, 2008
Publication year: 2008

Anomalous properties of localization in one-dimensional disordered models

Conference Paper
H. Cheraghchi , A. Habibi
Annual Physics Conference of Iran, Kashan University, Kashan - August, 2008
Publication year: 2008

Negative Differential Resistance in Graphene Nanoribbon Junctions

Conference Paper
H. Cheraghchi , K. Esfarjani
Publication year: 2007

Metal-Insulator Transition in a ternary model with long-range correlated disorder

ISI Paper
A. Esmailpour , H. Cheraghchi , P. Carpena , M. R. Rahimi Tabar
Journal of Statistical Mechanics: Theory and Experiment - , , P09014 - January, 2007
Publication year: 2007

Abstract

We study the metal–insulator transition of the one-dimensional diagonal Anderson ternary model with long range correlated disorder. The starting point of the model corresponds to a ternary alloy (i.e. with three possible on-site energies), and shows a metal–insulator transition when the random distribution of site energies is assumed to have a power spectrum S(k) propto 1/k^{(2alpha-1)} . In this paper, we define a purity parameter for the ternary alloy which adjusts the occupancy probability of site potentials, and for any given α we calculate the critical purity parameter for which extended states are obtained. In this way, we show that the ternary alloy requires weaker correlations than the binary alloy to present a phase transition from localized to extended states. A phase diagram which separates the extended regime from the localized one for the ternary alloy is presented, obtained as the critical purity parameter in terms of the corresponding correlation exponent.

The calculation of the eigenvalues spectrum of atoms with the full-filled electron shells in the Restricted Hartree-Fock Approximation

Conference Paper
V. Chegeni , H. Cheraghchi , M. R. Sarkardei
The 12th Gava-Zang meeting on condensed matter physics, Institute for advanced studies in basic science, Zanjan, Iran - May, 2006
Publication year: 2006

Statistical properties of a localization-delocalization transition induced by correlated disorder

ISI Paper
H. Cheraghchi , S. M. Fazeli
Journal of Statistical Mechanics: Theory and Experiment - , , P1004 - January, 2006
Publication year: 2006

Scaling properties of one-dimensional off-diagonal disorder

ISI Paper
H. Cheraghchi
Journal of Statistical Mechanics: Theory and Experiment - , , P1006 - January, 2006
Publication year: 2006

Abstract

Validity of the single-parameter scaling (SPS) in the one-dimensional Anderson model with purely off-diagonal disorder is studied. It is shown that the localized region with standard symmetry is divided into two regimes: SPS and non-SPS. Moreover, the scaling relations for the Lyapunov exponent are proposed for these two regimes. In the non-SPS regime, in addition to the localization length, there exists a new length scale which is related to the integral density of states. A physical interpretation of the new length is as the crossover length which separates regions with chiral symmetry from those with standard symmetry.

Scaling properties of one-dimensional off-diagonal disorder

Conference Paper
H. Cheraghchi , K. Esfarjani
College on Physics of Nano-Devices, the Abdus Salam International Centre for Theoretical Physics (ICTP) , Miramare, Trieste, Italy - July, 2006
Publication year: 2006

Scaling properties of one-dimensional off-diagonal disorder

Conference Paper
H. Cheraghchi , K. Esfarjani
The 12th Gava-Zang meeting on condensed matter physics, Institute for advanced studies in basic science, Zanjan, Iran - May, 2006
Publication year: 2006

Metal-Insulator Transition in one dimensional systems with long-range correlated hopping disorder

Conference Paper
H. Cheraghchi , S. M. Fazeli , K. Esfarjani
The 12th Gava-Zang meeting on condensed matter physics, Institute for advanced studies in basic science, Zanjan, Iran - May, 2006
Publication year: 2006

Localization Properties of one dimensional correlated off-diagonal disorder

Conference Paper
H. Cheraghchi , S. M. Fazeli , K. Esfarjani
(a) Conference on Strongly Interacting Systems at the Nanoscale (8-12 Aug 2005) (b) School on Quantum Phase Transitions and Non-Equilibrium Phenomena in Cold Atomic Gases (11-22 July 2005), the Abdus Salam International Centre for Theoretical Physics (ICTP) , Miramare, Trieste, Italy - August, 2005
Publication year: 2005

Localization - delocalization transition in a one-dimensonal system with long-range correlated off-diagonal disorder"

ISI Paper
H. Cheraghchi , S. M. Fazeli , K. Esfarjani
Physical Review. B. - 174207, 72, 8 - November, 2005
Publication year: 2005

Abstract:

The localization behavior of the one-dimensional Anderson model with correlated and uncorrelated purely off-diagonal disorder is studied. Using the transfer matrix method, we derive an analytical expression for the localization length at the band center in terms of the pair correlation function. It is proved that for long-range correlated hopping disorder, a localization-delocalization transition occurs at the critical Hurst exponent Hc =1/2 when the variance of the logarithm of hopping “lnt” is kept fixed with system size N. Numerically, this transition can be expanded to the vicinity of the band center. Based on numerical calculations, finite-size scaling relations are postulated for the localization length near the band center E0 in terms of the system parameters E,N,H, and lnt. D

Delocalization states in one dimensional system with special configuration of off-diagonal elements

Conference Paper
H. Cheraghchi , K. Esfarjani
The 7 th Condensed Matter Conference , Elmo-Sanat university of Iran, Tehran, Iran - January, 2005
Publication year: 2005

Long range coulomb interaction in Quantum Wire

Conference Paper
H. Cheraghchi , K. Esfarjani
The 10th Gava-Zang meeting on condensed matter physics, Institute for advanced studies in basic science, Zanjan, Iran - May, 2004
Publication year: 2004

Investigation of Disorder Effect on Density of States by CPA

Conference Paper
H. Cheraghchi , K. Esfarjani
The 6 th Condensed Matter Conference ,Yazd, Iran - February, 2003
Publication year: 2003

Effect of Disorder and External Potential on the Electron Transport and I-V Curve of a Quantum Dot

Conference Paper
H. Cheraghchi , K. Esfarjani , M. Mardaani
The 9th Gava-Zang meeting on condensed matter physics, Institue for advanced studies in basic science, Zanjan, Iran - May, 2003
Publication year: 2003