scholarly journals Intrinsic Spin-Orbit Coupling in Zigzag and Armchair Graphene Nanoribbons

2011 ◽  
Vol 2011 ◽  
pp. 1-7
Author(s):  
Ying Li ◽  
Erhu Zhang ◽  
Baihua Gong ◽  
Shengli Zhang
Keyword(s):  
Graphene Nanoribbons ◽  
Tight Binding ◽  
Geometrical Parameters ◽  
Spin Orbit Coupling ◽  
Spin Orbit ◽  
Binding Model ◽  
Tight Binding Approximation ◽  
Energy Gaps ◽  
Armchair Graphene Nanoribbons ◽  
Armchair Graphene

Starting from a tight-binding model, we derive the energy gaps induced by intrinsic spin-orbit (ISO) coupling in the low-energy band structures of graphene nanoribbons. The armchair graphene nanoribbons may be either semiconducting or metallic, depending on their widths in the absence of ISO interactions. For the metallic ones, the gaps induced by ISO coupling decrease with increasing ribbon widths. For the ISO interactions, we find that zigzag graphene nanoribbons with odd chains still have no band gaps while those with even chains have gaps with a monotonic decreasing dependence on the widths. First-principles calculations have also been carried out, verifying the results of the tight-binding approximation. Our paper reveals that the ISO interaction of graphene nanoribbons is governed by their geometrical parameters.

Spin–orbit coupling prevents spin channel suppression of transition metal atoms on armchair graphene nanoribbons

2018 ◽  
Vol 20 (47) ◽  
pp. 29826-29832 ◽  
Author(s):  
W. Y. Rojas ◽  
Cesar E. P. Villegas ◽  
A. R. Rocha
Keyword(s):  
Density Functional ◽  
Graphene Nanoribbons ◽  
Orbit Coupling ◽  
Spin Orbit Coupling ◽  
Spin Orbit ◽  
Functional Theory ◽  
Transition Metal Atoms ◽  
Spin Polarized ◽  
Armchair Graphene Nanoribbons ◽  
Armchair Graphene

We investigate the spin-dependent electronic and transport properties of armchair graphene nanoribbons including spin–orbit coupling due to the presence of nickel and iridium adatoms by using ab initio calculations within the spin-polarized density functional theory and non-equilibrium Green's function formalism.

SPIN-ORBIT COUPLING IN GRAPHENE UNDER UNIAXIAL STRAIN: TIGHT-BINDING APPROACH AND FIRST-PRINCIPLES CALCULATIONS

2011 ◽  
Vol 25 (11) ◽  
pp. 823-830 ◽  
Author(s):  
BAIHUA GONG ◽  
XIN-HUI ZHANG ◽  
ER-HU ZHANG ◽  
SHENG-LI ZHANG
Keyword(s):  
Band Gap ◽  
First Principles ◽  
Tight Binding ◽  
Uniaxial Strain ◽  
Orbit Coupling ◽  
Spin Orbit Coupling ◽  
Spin Orbit ◽  
First Principles Calculations ◽  
Binding Model ◽  
Tight Binding Approximation

Tuning the spin-orbit coupling (SOC) in graphene is highly desired for its application in spintronics. In this paper, we calculated the band gap induced by SOC in graphene under uniaxial strain from a tight-binding model, and found that the band gap has a monotonic increasing dependence on the strain in the range of -20% to 15%. Our results suggest that strain can be used as a reversible and controllable way to tune the SOC in graphene. First-principles calculations were performed, confirming the results of tight-binding approximation.

scholarly journals Role Played by Edge-Defects in the Optical Properties of Armchair Graphene Nanoribbons

Nanomaterials ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 3229
Author(s):  
Thi-Nga Do ◽  
Godfrey Gumbs ◽  
Danhong Huang ◽  
Bui D. Hoi ◽  
Po-Hsin Shih
Keyword(s):  
Optical Properties ◽  
Graphene Nanoribbons ◽  
Tight Binding ◽  
Edge States ◽  
Binding Model ◽  
Edge Defect ◽  
Flat Bands ◽  
Edge Defects ◽  
Armchair Graphene Nanoribbons ◽  
Armchair Graphene

We explore the implementation of specific optical properties of armchair graphene nanoribbons (AGNRs) through edge-defect manipulation. This technique employs the tight-binding model in conjunction with the calculated absorption spectral function. Modification of the edge states gives rise to the diverse electronic structures with striking changes in the band gap and special flat bands at low energy. The optical-absorption spectra exhibit unique excitation peaks, and they strongly depend on the type and period of the edge extension. Remarkably, there exist the unusual transition channels associated with the flat bands for selected edge-modified systems. We discovered the special rule governing how the edge-defect influences the electronic and optical properties in AGNRs. Our theoretical prediction demonstrates an efficient way to manipulate the optical properties of AGNRs. This might be of importance in the search for suitable materials designed to have possible technology applications in nano-optical, plasmonic and optoelectronic devices.

scholarly journals Role Played by Edge-Defects in the Optical Properties of Armchair Graphene Nanoribbons

2021 ◽  
Author(s):  
Thi-Nga Do ◽  
Godfrey Gumbs ◽  
Danhong Huang ◽  
D. Hoi Bui ◽  
Po-Hsin Shih
Keyword(s):  
Optical Properties ◽  
Graphene Nanoribbons ◽  
Tight Binding ◽  
Edge States ◽  
Binding Model ◽  
Edge Defect ◽  
Flat Bands ◽  
Edge Defects ◽  
Armchair Graphene Nanoribbons ◽  
Armchair Graphene

We explore the implementation of specific optical properties of armchair graphene nanoribbons (AGNRs) through edge-defect manipulation. This technique employs the tight-binding model in conjunction with the calculated absorption spectral function. Modification of the edge states gives rise to the diverse electronic structures with striking changes in the band gap and special flat bands at low energy. The optical-absorption spectra exhibit exotic excitation peaks and they strongly depend on the type and period of the edge extension. Remarkably, there exist the unusual transition channels associated with the flat bands for selected edge-modified systems. We discover the special rule governing how the edge-defect influences the electronic and optical properties in AGNRs. Our theoretical prediction demonstrates an efficient way to manipulate the optical properties of AGNRs. This might be of importance in the search for suitable materials designed to have possible technology applications in nano-optical, plasmonic and optoelectronic devices.

scholarly journals Unified Drain Current Model of Armchair Graphene Nanoribbons with Uniaxial Strain and Quantum Effect

2014 ◽  
Vol 2014 ◽  
pp. 1-7 ◽  
Author(s):  
EngSiew Kang ◽  
Razali Ismail
Keyword(s):  
Quantum Confinement ◽  
Graphene Nanoribbons ◽  
Quantum Effect ◽  
Current Model ◽  
Tight Binding ◽  
Drain Current ◽  
Published Data ◽  
Tight Binding Approximation ◽  
Armchair Graphene Nanoribbons ◽  
Armchair Graphene

A unified current-voltageI-Vmodel of uniaxial strained armchair graphene nanoribbons (AGNRs) incorporating quantum confinement effects is presented in this paper. TheI-Vmodel is enhanced by integrating both linear and saturation regions into a unified and precise model of AGNRs. The derivation originates from energy dispersion throughout the entire Brillouin zone of uniaxial strained AGNRs based on the tight-binding approximation. Our results reveal the modification of the energy band gap, carrier density, and drain current upon strain. The effects of quantum confinement were investigated in terms of the quantum capacitance calculated from the broadening density of states. The results show that quantum effect is greatly dependent on the magnitude of applied strain, gate voltage, channel length, and oxide thickness. The discrepancies between the classical calculation and quantum calculation were also measured and it has been found to be as high as 19% drive current loss due to the quantum confinement. Our finding which is in good agreement with the published data provides significant insight into the device performance of uniaxial strained AGNRs in nanoelectronic applications.

Tight-Binding Approximation Calculation on the Electronic Structure of Graphene and Graphene Nanoribbons

2013 ◽  
Vol 341-342 ◽  
pp. 199-203 ◽  
Author(s):  
Hong Xia Wang ◽  
Cheng Lai Yang ◽  
You Zhang Zhu ◽  
Ni Chen Yang
Keyword(s):  
Electronic Structure ◽  
Energy Gap ◽  
Graphene Nanoribbons ◽  
Tight Binding ◽  
Periodic Boundary Conditions ◽  
Tight Binding Approximation ◽  
Width Direction ◽  
Armchair Graphene Nanoribbons ◽  
Approximation Calculation ◽  
Armchair Graphene

The electronic structure expression of graphene was derived using tight-binding approxi-mation method. According to periodic boundary conditions in width direction of graphene nanorib-bons wave vector, the electronic structure analytical expression of armchair graphene nanoribbons was deduced, and the energy band curve were given. The conditions of graphene nanoribbons being metal or semiconductor were obtained. The results show that when nanoribbons width meetsL=3na/2, the energy gap is zero and armchair graphene nanoribbons behave as the metallic. With the increase of the nanoribbons width, the energy gap of semiconducting nanoribbons decreases. The electronic properties of graphene nanoribbons are closely related to their geometry. The graphene nanoribbons can be modulated into metal or semiconductor with different band gap by controlling their width.

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