Effects of Geometry and Symmetry on Electron Transport through Graphene–Carbon-Chain Junctions

Dong, Yujing; Wang, Xuefeng; Zhai, Ming-Xing; Wu, Jianchun; Zhou, Liping; Han, Qi; Wu, Xuemei

doi:10.1021/jp405318b

Cited by 20 publications

(12 citation statements)

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“…20 Specically, the edge magnetism exists in zigzag GNRs (ZGNRs) though graphene is a nonmagnetic material 21 and their transversal geometry symmetry can play a key role in determining their transport properties. 22,23 Employing doping and other modication techniques, we can easily manipulate the magnetic properties in ZGNRs and might make them important materials for spintronics.…”

Section: Introductionmentioning

confidence: 99%

Giant magnetoresistance and spin Seebeck coefficient in zigzag α-graphyne nanoribbons

et al. 2014

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We investigate the spin-dependent electric and thermoelectric properties of ferromagnetic zigzag α-graphyne nanoribbons (ZαGNRs) using density-functional theory combined with non-equilibrium Green's function method. A giant magnetoresistance is obtained in the pristine even-width ZαGNRs and can be as high as 10(6)%. However, for the doped systems, a large magnetoresistance behavior may appear in the odd-width ZαGNRs rather than the even-width ones. This suggests that the magnetoresistance can be manipulated in a wide range by the dopants on the edges of ZαGNRs. Another interesting phenomenon is that in the B- and N-doped even-width ZαGNRs the spin Seebeck coefficient is always larger than the charge Seebeck coefficient, and a pure-spin-current thermospin device can be achieved at specific temperatures.

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Section: Introductionmentioning

confidence: 99%

Giant magnetoresistance and spin Seebeck coefficient in zigzag α-graphyne nanoribbons

et al. 2014

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“…17 Recently, Dong et al studied the electron transport properties of the CACs sandwiched between two ZGNRs. 18 They found that the electron transport near the Fermi level could be well controlled by the position and the number of the CACs. In addition, a carbon-based molecular device can be fabricated by inserting a diphenyl-dimethyl between a CAC, which are linked to gold electrodes through thiol-gold bond.…”

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confidence: 99%

“…The n-ZGNR electrodes have two zigzag edges along the Z direction, and here n (¼6) is the number of the dimer across the ribbon width along the X direction. Similar to Dong's studies, 18 we choose a threemembered-ring structure in the contact point between the CAC and 6-ZGNRs. All the edge carbon atoms are terminated by hydrogen atoms.…”

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confidence: 99%

Spin-resolved Fano resonances induced large spin Seebeck effects in graphene-carbon-chain junctions

Liu

Zhang

Feng

et al. 2014

Applied Physics Letters

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We propose a high-efficiency thermospin device constructed by a carbon atomic chain sandwiched between two ferromagnetic (FM) zigzag graphene nanoribbon electrodes. In the low-temperature regime, the magnitude of the spin figure of merit is nearly equal to that of the corresponding charge figure of merit. This is attributed to the appearances of spin-resolved Fano resonances in the linear conductance spectrum resulting from the quantum interference effects between the localized states and the expanded states. The spin-dependent Seebeck effect is obviously enhanced near these Fano resonances with the same spin index; meanwhile, the Seebeck effect of the other spin component has a smaller value due to the smooth changing of the linear conductance with the spin index. Thus, a large spin Seebeck effect is achieved, and the magnitude of the spin figure of merit can reach 1.2 at T = 25 K. Our results indicate that the FM graphene-carbon-chain junctions can be used to design the high-efficiency thermospin devices.

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“…For the exchange-correlation potential, the generalized gradient approximation given by Perdew−Burke−Ernzerhof (PBE) has been employed. This procedure has been proven to be successful in predicting magnetic states in graphene quantum dots, 42 as well as for electron transport through graphene-carbon-chain junctions, 43 in the presence of uniform electric fields. During the process of geometry relaxation, under external electric fields with magnitudes in the range of |E ⃗ ext | = 0.0−5.0 V/nm, the constituent atoms are allowed to relax until forces decrease below 10 −3 eV/Å.…”

Section: Methodsmentioning

confidence: 99%

Electric-Field Control of Spin-Polarization and Semiconductor-to-Metal Transition in Carbon-Atom-Chain Devices

et al. 2017

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We propose hybrid molecular systems containing small carbon atomic chains interconnected by graphene-like flakes, theoretically predicted as true energy minima, as low-dimensional structures that may be useful in electronic devices at the limit of the atomic miniaturization. The effects of an external electric field applied along the direction of the carbon chains indicate that it is possible to control energy gap and spinpolarization with sufficiently high strength, within the limit of the structural restoring of the systems. In this sense, by applying electric fields with magnitudes in the 1-5 V/nm range, we obtain semiconductor-to-metallic transitions for all odd-numbered carbonchain systems proposed here. Furthermore, high-spin-to-low-spin transitions are determined for these systems as a function of the electric field magnitude. In the case of the even-numbered carbon-chain systems, the overall electric field effect is pushing electron density near the Fermi level, leading to a gapless or metallic regime at 3.0 V/nm. An electric-field control of the spin-polarization of these latter systems is only achieved by doping the extremities of the graphene-like terminations with sulfur atoms. This finding, however, is beneficial for applications of these systems in spin-controlled carbon-based devices connected by gold electrodes, even in the presence of a weak spinorbit coupling.

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Effects of Geometry and Symmetry on Electron Transport through Graphene–Carbon-Chain Junctions

Cited by 20 publications

References 50 publications

Giant magnetoresistance and spin Seebeck coefficient in zigzag α-graphyne nanoribbons

Giant magnetoresistance and spin Seebeck coefficient in zigzag α-graphyne nanoribbons

Spin-resolved Fano resonances induced large spin Seebeck effects in graphene-carbon-chain junctions

Electric-Field Control of Spin-Polarization and Semiconductor-to-Metal Transition in Carbon-Atom-Chain Devices

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