We explore the electronic and transport properties of zigzag graphene nanoribbons （GNRs） with nitrogen-vacancy defects by performing fully self-consistent spin-polarized density functional theory calculations combin...We explore the electronic and transport properties of zigzag graphene nanoribbons （GNRs） with nitrogen-vacancy defects by performing fully self-consistent spin-polarized density functional theory calculations combined with non-equilibrium Green＇s function technique. We observe robust negative di erential resistance （NDR） effect in all examined molecular junctions. Through analyzing the calculated electronic structures and the bias-dependent transmission coefficients, we find that the narrow density of states of electrodes and the bias-dependent effective coupling between the central molecular orbitals and the electrode subbands are responsible for the observed NDR phenomenon. In addition, the obvious di erence of the transmission spectra of two spin channels is observed in some bias ranges, which leads to the near perfect spin-filtering effect. These theoretical findings imply that GNRs with nitrogenvacancy defects hold great potential for building molecular devices.展开更多
We theoretically investigate the spin filtering transport of double parallel quantum wires(QWs) side-coupled to a grapheme sheet and sandwiched between two ferromagnetic(FM) leads.The dependences of the wire-graphene ...We theoretically investigate the spin filtering transport of double parallel quantum wires(QWs) side-coupled to a grapheme sheet and sandwiched between two ferromagnetic(FM) leads.The dependences of the wire-graphene coupling strength,wire-wire coupling strength,as well as the spin polarization of the ferromagnetic leads are studied.It is found that the wire-graphene coupling strength tends to reduce the current and the wire-wire coupling strength can first reinforce and then decrease the current.The spin polarization strength has an enhanced(identical) effect on the current under the parallel(anti-parallel) alignment of the FM leads,which gives rise to an obvious spin-filter and tunnel magnetoresistance(TMR) effect.Our results suggest that such a theoretical model can stimulate some experimental investigations about the spin-filter devices.展开更多
We design a Blatter radical-based molecular spintronic device, and investigate its spin-polarized transport properties using density functional theory and non-equilibrium Green's function technique. High-performan...We design a Blatter radical-based molecular spintronic device, and investigate its spin-polarized transport properties using density functional theory and non-equilibrium Green's function technique. High-performance spin-rectifying and spin-filtering effects are realized. The physical mechanism is explained by the spin-resolved bias voltage-dependent transmission spectra, the energy levels of the corresponding molecular projected self-consistent Hamiltonian orbitals, and their spatial distributions. The results demonstrate that the Blatter radical has great potential in the development of highperformance multifunctional molecular spintronic devices.展开更多
A recent theoretical estimation indicated that the NM/FI/FI/NM double spin-filter junction (DSFJ, here the NM and FI represent the nonmagnetic electrode and the ferromagnetic insulator (semiconductor) spacer, respecti...A recent theoretical estimation indicated that the NM/FI/FI/NM double spin-filter junction (DSFJ, here the NM and FI represent the nonmagnetic electrode and the ferromagnetic insulator (semiconductor) spacer, respectively) could have very high tunneling magnetoresistance (TMR) at zero bias. To meet the requirement in research and application of the magnetoresistance devices, we have calculated the dependences of tunneling magnetoresistance of DSF J on the bias (volt-age), the thicknesses of ferromagnetic insulators (semiconductors) and the average barrier height. Our results show that except its very high value, the TMR of DSFJ does not decrease montonously and rapidly with rising bias, but increase slowly at first and decrease then after having reached a maximum value. This feature is in distinct contrast to the ordinary magnetic tunnel junction FM/NI/FM (FM and NI denote the ferromagnetic electrode and the nonmagnetic insulator (semiconductor) spacer, respectively), and is of benefit to the use of DSFJ as a magnetoresistance device.展开更多
基金This work was partially supported by the National Natural Science Foundation of China （No.20903003 and No.21273208）, the Anhui Provincial Natural Science Foundation （No.1408085QB26）, the China Postdoctoral Science Foundation （No.2012M511409）, the Supercomputer Center of Chinese Academy of Sciences, and University of Science and Technology of China and Shanghai Supercomputer Centers.
文摘We explore the electronic and transport properties of zigzag graphene nanoribbons （GNRs） with nitrogen-vacancy defects by performing fully self-consistent spin-polarized density functional theory calculations combined with non-equilibrium Green＇s function technique. We observe robust negative di erential resistance （NDR） effect in all examined molecular junctions. Through analyzing the calculated electronic structures and the bias-dependent transmission coefficients, we find that the narrow density of states of electrodes and the bias-dependent effective coupling between the central molecular orbitals and the electrode subbands are responsible for the observed NDR phenomenon. In addition, the obvious di erence of the transmission spectra of two spin channels is observed in some bias ranges, which leads to the near perfect spin-filtering effect. These theoretical findings imply that GNRs with nitrogenvacancy defects hold great potential for building molecular devices.
基金Supported by the National Natural Science Foundation of China under Grant Nos.11174214,11204192the NSAF Joint Fund Jointly set up by the National Natural Science Foundation of Chinathe Chinese Academy of Engineering Physics under Grant Nos.U1230201and U1430117
文摘We theoretically investigate the spin filtering transport of double parallel quantum wires(QWs) side-coupled to a grapheme sheet and sandwiched between two ferromagnetic(FM) leads.The dependences of the wire-graphene coupling strength,wire-wire coupling strength,as well as the spin polarization of the ferromagnetic leads are studied.It is found that the wire-graphene coupling strength tends to reduce the current and the wire-wire coupling strength can first reinforce and then decrease the current.The spin polarization strength has an enhanced(identical) effect on the current under the parallel(anti-parallel) alignment of the FM leads,which gives rise to an obvious spin-filter and tunnel magnetoresistance(TMR) effect.Our results suggest that such a theoretical model can stimulate some experimental investigations about the spin-filter devices.
基金Project supported by the Natural Science Foundation of Shandong Province, China (Grant No. ZR2021MA059)。
文摘We design a Blatter radical-based molecular spintronic device, and investigate its spin-polarized transport properties using density functional theory and non-equilibrium Green's function technique. High-performance spin-rectifying and spin-filtering effects are realized. The physical mechanism is explained by the spin-resolved bias voltage-dependent transmission spectra, the energy levels of the corresponding molecular projected self-consistent Hamiltonian orbitals, and their spatial distributions. The results demonstrate that the Blatter radical has great potential in the development of highperformance multifunctional molecular spintronic devices.
基金the National Natural Science Foundation of China(Grant No.10074075)the Department of Science and Technology under the National Key Project of Basic Research(Grant No.G1999064509).
文摘A recent theoretical estimation indicated that the NM/FI/FI/NM double spin-filter junction (DSFJ, here the NM and FI represent the nonmagnetic electrode and the ferromagnetic insulator (semiconductor) spacer, respectively) could have very high tunneling magnetoresistance (TMR) at zero bias. To meet the requirement in research and application of the magnetoresistance devices, we have calculated the dependences of tunneling magnetoresistance of DSF J on the bias (volt-age), the thicknesses of ferromagnetic insulators (semiconductors) and the average barrier height. Our results show that except its very high value, the TMR of DSFJ does not decrease montonously and rapidly with rising bias, but increase slowly at first and decrease then after having reached a maximum value. This feature is in distinct contrast to the ordinary magnetic tunnel junction FM/NI/FM (FM and NI denote the ferromagnetic electrode and the nonmagnetic insulator (semiconductor) spacer, respectively), and is of benefit to the use of DSFJ as a magnetoresistance device.
