The spin-dependent conductance and magnetoresistance ratio (MRR) for a semiconductor heterostructures consisting of two magnetic barriers with different height and space have been investigated by the transfer-matrix...The spin-dependent conductance and magnetoresistance ratio (MRR) for a semiconductor heterostructures consisting of two magnetic barriers with different height and space have been investigated by the transfer-matrix method. It is shown that the splitting of the conductance for parallel and antiparallel magnetization configurations results in tremendous spin-dependent MRR, and the maximal MRRs reach 5300% and 3800% for the magnetic barrier spaces W = 81.3 and 243.9 nm, respectively. The obtained spin-filtering transport property of nanostructures with magnetic barriers may be useful to magnetic-barrier-based spintronics.展开更多
We study the spin-dependent thermopower in a double-quantum-dot(DQD) embedded between the left and right two-dimensional electron gases(2DEGs) in doped quantum wells under an in-plane magnetic field. When the separati...We study the spin-dependent thermopower in a double-quantum-dot(DQD) embedded between the left and right two-dimensional electron gases(2DEGs) in doped quantum wells under an in-plane magnetic field. When the separation between the DQD is smaller than the Fermi wavelength in the 2DEGs, the asymmetry in the dots' energy levels leads to pronounced quantum interference effects characterized by the Dicke line-shape of the conductance, which are sensitive to the properties of the 2DEGs. The magnitude of the thermopower, which denotes the generated voltage in response to an infinitesimal temperature difference between the two 2DEGs under vanishing charge current, will be obviously enhanced by the Dicke effect. The application of the in-plane magnetic field results in the polarization of the spin-up and spin-down conductances and thermopowers, and enables an efficient spin-filter device in addition to a tunable pure spin thermopower in the absence of its charge counterpart.展开更多
Oxygen deficient Nd0.67Sr0.33MnO3-δ ceramic samples were prepared using conventional ceramic technology. A colossal electroresistance (CER) effect was found in Nd0.67Sr0.33MnO3-δ series. The electrical transport is ...Oxygen deficient Nd0.67Sr0.33MnO3-δ ceramic samples were prepared using conventional ceramic technology. A colossal electroresistance (CER) effect was found in Nd0.67Sr0.33MnO3-δ series. The electrical transport is magnetically coupled and spin-dependent over grain or phase boundaries. Electrical-field-induced changes of the spin array orientations inside of and between the magnetic domains by grain or phase boundaries have to be concluded for the strong electroresistive effect in Nd0.67Sr0.33MnO3-δ series.展开更多
It is commonly known that the hydrodynamic equations can be derived from the Boltzmann equation. In this paper, we derive similar spin-dependent balance equations based on the spinor Boltzmann equation. Besides the us...It is commonly known that the hydrodynamic equations can be derived from the Boltzmann equation. In this paper, we derive similar spin-dependent balance equations based on the spinor Boltzmann equation. Besides the usual charge current, heat current, and pressure tensor, we also explore the characteristic spin accumulation and spin current as well as the spin-dependent pressure tensor and heat current in spintronics. The numerical results of these physical quantities are demonstrated using an example of spin-polarized transport through a mesoscopic ferromagnet.展开更多
We investigate a one-dimensional two-component system in an optical lattice of attractive interactions under a spin- dependent external potential. Based on the density-matrix renormalization group methods, we obtain i...We investigate a one-dimensional two-component system in an optical lattice of attractive interactions under a spin- dependent external potential. Based on the density-matrix renormalization group methods, we obtain its phase diagram as a function of the external potential imbalance and the strength of the attractive interaction through the analysis on the density profiles and the momentum pair correlation functions. We find that there are three different phases in the system, a coexisted fully polarized and Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) phase, a normal polarized phase, and a Bardeen- Cooper-Schrieffer (BCS) phase. Different from the systems of spin-independent external potential, where the FFLO phase is normally favored by the attractive interactions, in the present situation, the FFLO phases are easily destroyed by the attractive interactions, leading to the normal polarized or the BCS phase.展开更多
We present a phase-and spin-dependent manipulation of leakage of a Majorana mode into a double quantum dot.We study the density of states(DOS)to show the effect of phase change factor on the Majorana leakage into(out)...We present a phase-and spin-dependent manipulation of leakage of a Majorana mode into a double quantum dot.We study the density of states(DOS)to show the effect of phase change factor on the Majorana leakage into(out)of a double quantum dot.The DOS is derived from the Green's function of the quantum dot by the equation of motion method,and exhibits a formant structure whenφ=0,2πand a resonance shape whenφ=0.5πand 1.5π.Also,it changes more strongly under the spin-polarized coefficient than the non-polarized lead.Such a theoretical model can be modified to explore the spin-dependent effect in the hybrid Majorana quantum dot system.展开更多
Spin-polarized transport through a precessing magnetic spin coupled to ferromagnetic electrodes is studied using a non-equilibrium Green's function approach. The characteristic of conductance is obtained at zero temp...Spin-polarized transport through a precessing magnetic spin coupled to ferromagnetic electrodes is studied using a non-equilibrium Green's function approach. The characteristic of conductance is obtained at zero temperature. We find that competition between spin-exchange interaction on the spin site and spin-orbit interaction in the barriers dominates the resonant behavior of conductance. In a parallel configuration, conductance peaks have identical amplitude. With the angle θ increasing, the width of resonant peaks is broadened or narrowed for different spin coherent states. In an anti-parallel case, spin-flip tunneling in the barriers will essentially enhance amplitude of the conductance peak.展开更多
The extra heat generation in spin transport is usually interpreted in terms of the spin relaxation. Reformulating the heat generation rate, we find alternative current-force pairs without cross effects, which enable u...The extra heat generation in spin transport is usually interpreted in terms of the spin relaxation. Reformulating the heat generation rate, we find alternative current-force pairs without cross effects, which enable us to interpret the product of each pair as a distinct mechanism of heat generation. The results show that the spin-dependent part of the heat generation includes two terms. One is proportional to the square of the spin accumulation and arises from the spin relaxation. However, the other is proportional to the square of the spin-accumulation gradient and should be attributed to another mechanism, the spin diffusion. We illustrate the characteristics of the two mechanisms in a typical spin valve with a finite nonmagnetic spacer layer.展开更多
Method is developed for self-consistent calculation of the energy spectrum of free energy and electrical disordered crystals. Processes of electron scattering on the ionic core potential of different sort, fluctuation...Method is developed for self-consistent calculation of the energy spectrum of free energy and electrical disordered crystals. Processes of electron scattering on the ionic core potential of different sort, fluctuations of charge, spin density and lattice vibrations are taken into account. Electronic states of the system are described using tight binding multiband model. The nature of the spin-dependent electron transport of carbon nanotubes with chromium atoms adsorbed on the surface is explained. The value of the spin polarization of electron transport is determined by the difference of the partial densities of states of electrons with opposite spin projection at the Fermi level and the difference between the relaxation times of electron states. The value of the spin polarization of the electric current increases with increasing of Cr atoms concentration and magnitude of the external magnetic field.展开更多
By employing non-equilibrium Green's function combined with the spin-polarized density-functional theory, we investigate the spin-dependent electronic transport properties of armchair arsenene nanoribbons(a As NRs)...By employing non-equilibrium Green's function combined with the spin-polarized density-functional theory, we investigate the spin-dependent electronic transport properties of armchair arsenene nanoribbons(a As NRs). Our results show that the spin-metal and spin-semiconductor properties can be observed in a As NRs with different widths. We also find that there is nearly 100% bipolar spin-filtering behavior in the a As NR-based device with antiparallel spin configuration. Moreover, rectifying behavior and giant magnetoresistance are found in the device. The corresponding physical analyses have been given.展开更多
Using the nonequilibrium Green's function method combined with the tight-binding Hamiltonian, we theoretically investigate the spin-dependent transmission probability and spin Seebeck coefficient of a crossed armchai...Using the nonequilibrium Green's function method combined with the tight-binding Hamiltonian, we theoretically investigate the spin-dependent transmission probability and spin Seebeck coefficient of a crossed armchair-edge graphene nanoribbon (AGNR) superl'attice p-n junction under a perpendicular magnetic field with a ferromagnetic insulator, where junction widths Wi of 40 and 41 are considered to exemplify the effect of semiconducting and metallic AGNRs, respectively. A pristine AGNR system is metallic when the transverse layer m = 3j + 2 with a positive integer j and an insulator otherwise. When stubs are present, a semiconducting AGNR junction with width W1= 40 always shows metallic behavior regardless of the potential drop magnitude, magnetization strength, stub length, and per- pendicular magnetic field strength. However, metallic or semiconducting behavior can be obtained from a metallic AGNR junction with Wi = 41 by adjusting these physical parameters. Furthermore, a metal-to-semiconductor transition can be obtained for both superlattice p-n junctions by adjust- ing the number of periods of the superlattice. In addition, the spin-dependent Seebeck coefficient and spin Seebeck coefficient of the two systems are of the same order of magnitude owing to the appearance of a transmission gap, and the maximum absolute value of the spin Seebeck coefficient reaches 370 μV/K when the optimized parameters are used. The calculated results offer new possi- bilities for designing electronic or heat-spintronic nanodevices based on the graphene superlattice p-n junction.展开更多
We propose to use Bloch oscillation of ultra-cold atoms in a spin-dependent optical lattice to prepare Schro¨dinger cat states.Depending on its internal state,an atom feels different periodic potentials and thus ...We propose to use Bloch oscillation of ultra-cold atoms in a spin-dependent optical lattice to prepare Schro¨dinger cat states.Depending on its internal state,an atom feels different periodic potentials and thus has different energy band structures for its center-of-mass motion.Consequently,under the same gravity force,the wave packets associated with different internal states perform Bloch oscillation of different amplitudes in space and in particular they can be macroscopically displaced with respect to each other.In this manner,a cat state can be prepared.展开更多
Effects of soft-magnetic MnZn ferrite (Mn0.5Zn0.5Fe2O4, MZF) and hard-magnetic Ba ferrite (BaO.6Fe2O3, BaM) on the structure and magnetic transport properties of [La2/3Srl/3MnO3] (LSMO)/(x) [ferrites] (ferrit...Effects of soft-magnetic MnZn ferrite (Mn0.5Zn0.5Fe2O4, MZF) and hard-magnetic Ba ferrite (BaO.6Fe2O3, BaM) on the structure and magnetic transport properties of [La2/3Srl/3MnO3] (LSMO)/(x) [ferrites] (ferrites=MZF, BaM) composites have been investigated. It was found that the inclusion of MZF phase reduces magnetization and ferromagnetic-paramagnetic transition temperature (To) of the composites. With increasing the content of the dopants, the high-temperature magnetoresistance (MR) decreases, whereas low-temperature MR increases and reaches 42% at 150 K and x=0.1. However, for the LSMO/BaM composites, magnetization and ferromagneticparamagnetic transition temperature (To) decrease firstly as x〈5%, and then increase as x〉5%. The resistivity of the composites increases by five orders of magnitude at x=1% and is out of measured range at x=5%. High magnetic field has little effect on the resistivity and magnetoresistance originate from the pinning effect of BaM for the composites with x〉5%, which may grains.展开更多
The spin-dependent electronic transport properties of a zigzag zinc oxide(ZnO) nanoribbon are studied by using density functional theory with non-equilibrium Green's functions. We calculate the spin-polarized band...The spin-dependent electronic transport properties of a zigzag zinc oxide(ZnO) nanoribbon are studied by using density functional theory with non-equilibrium Green's functions. We calculate the spin-polarized band structure, projected density of states, Bloch states, and transmission spectrum of the ZnO nanoribbon. It is determined that all Bloch states are located at the edge of the ZnO nanoribbon. The spin-up transmission eigenchannels are contributed from Zn 4s orbital,whereas the spin-down transmission eigenchannels are contributed from Zn 4s and O 2p orbitals. By analyzing the current-voltage curves for the opposite spins of the ZnO nanoribbon device, negative differential resistance(NDR) and spin filter effect are observed. Moreover, by constructing the ZnO nanoribbon modified by the Zn-edge defect, the spin-up current is severely suppressed because of the destruction of the spin-up transmission eigenchannels. However, the spin-down current is preserved, thus resulting in the perfect spin filter effect. Our results indicate that the ZnO nanoribbon modulated by the edge defect is a practical design for a spin filter.展开更多
Using the first-principles method,the spin-dependent transport properties of a novel platform molecule containing a freestanding molecular wire is investigated by simulating the spin-polarized scanning tunneling micro...Using the first-principles method,the spin-dependent transport properties of a novel platform molecule containing a freestanding molecular wire is investigated by simulating the spin-polarized scanning tunneling microscope experiment with Ni tip and Au substrate electrodes.Transport calculations show that the total current increases as the tip gradually approaches to the substrate,which is consistent with the conductance obtained from previous experiment.More interestingly,the spin polarization(SP)of current modulated by compression effect has the completely opposite trend to the total current.Transmission analyses reveal that the reduction of SP of current with compression process originates from the promotion of spin-down electron channel,which is controlled by deforming the molecule wire.In addition,the density of states shows that the SP of current is directly affected by the organic–ferromagnetic spinterface.The weak orbital hybridization between the Ni tip and propynyl of molecule results in high interfacial SP,whereas the breaking of the C≡C triple of propynyl in favor of the Ni–C–C bond induces the strong orbital hybridization and restrains the interfacial SP.This work proposes a new way to control and design the SP of current through organic–ferromagnetic spinterface using functional molecular platform.展开更多
Based on the Green's function technique and the equation of motion approach, this paper theoretically studies the thermoelectric effect in parallel coupled double quantum dots (DQDs), in which Rashba spin-orbit int...Based on the Green's function technique and the equation of motion approach, this paper theoretically studies the thermoelectric effect in parallel coupled double quantum dots (DQDs), in which Rashba spin-orbit interaction is taken into account. Rashba spin^rbit interaction contributions, even in a magnetic field, are exhibited obviously in the double quantum dots system for the thermoelectric effect. The periodic oscillation of thermopower can be controlled by tunning the Rashba spin^rbit interaction induced phase. The interesting spin-dependent thermoelectric effects will arise which has important influence on thermoelectric properties of the studied system.展开更多
Controlling the spin transport at the single-molecule level,especially without the use of ferromagnetic contacts,becomes a focus of research in spintronics.Inspired by the progress on atomic-level molecular synthesis,...Controlling the spin transport at the single-molecule level,especially without the use of ferromagnetic contacts,becomes a focus of research in spintronics.Inspired by the progress on atomic-level molecular synthesis,through firstprinciples calculations,we investigate the spin-dependent electronic transport of graphene nanoflakes with side-bonded functional groups,contacted by atomic carbon chain electrodes.It is found that,by rotating the functional group,the spin polarization of the transmission at the Fermi level could be switched between completely polarized and unpolarized states.Moreover,the transition between spin-up and spin-down polarized states can also be achieved,operating as a dual-spin filter.Further analysis shows that,it is the spin-dependent shift of density of states,caused by the rotation,that triggers the shift of transmission peaks,and then results in the variation of spin polarization.Such a feature is found to be robust to the length of the nanoflake and the electrode material,showing great application potential.Those findings may throw light on the development of spintronic devices.展开更多
Based on the density functional theory combined with the nonequilibrium Green function methodology,we have studied the thermally-driven spin-dependent transport properties of a combinational molecular junction consist...Based on the density functional theory combined with the nonequilibrium Green function methodology,we have studied the thermally-driven spin-dependent transport properties of a combinational molecular junction consisting of a planar four-coordinate Fe molecule and a 15,16-dinitrile dihydropyrene/cyclophanediene molecule,with single-walled carbon nanotube bridge and electrode.Our results show that the magnetic field and light can effectively regulate the thermallydriven spin-dependent currents.Perfect thermal spin-filtering effect and good thermal switching effect are realized.The results are explained by the Fermi-Dirac distribution function,the spin-resolved transmission spectra,the spatial distribution of molecular projected self-consistent Hamiltonian orbitals,and the spin-resolved current spectra.On the basis of these thermally-driven spin-dependent transport properties,we have further designed three basic thermal spin molecular AND,OR,and NOT gates.展开更多
A bias-controlled spin-filter and spin memory is theoretically proposed, which consists of the junction with a singlemolecule magnet sandwiched between the nonmagnetic and ferromagnetic(FM) leads. By applying differen...A bias-controlled spin-filter and spin memory is theoretically proposed, which consists of the junction with a singlemolecule magnet sandwiched between the nonmagnetic and ferromagnetic(FM) leads. By applying different voltage pulses Vwriteacross the junction, the spin direction of the single-molecule magnet can be controlled to be parallel or anti-parallel to the magnetization of the FM lead, and the spin direction of SMM can be "read out" either by the magneto-resistance or by the spin current with another series of small voltage pulses V_(probe). It is shown that the polarization of the spin current is extremely high(up to 100%) and can be manipulated by the full-electric manner. This device scheme can be compatible with current technologies and has potential applications in high-density memory devices.展开更多
The Einstein-Podolsky-Rosen paradox is resolved dynamically by using spin-dependent quantum trajectories inferred from Dirac’s equation for a relativistic electron. The theory provides a practical computational metho...The Einstein-Podolsky-Rosen paradox is resolved dynamically by using spin-dependent quantum trajectories inferred from Dirac’s equation for a relativistic electron. The theory provides a practical computational methodology for studying entanglement versus disentanglement for realistic Hamiltonians.展开更多
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 10574042 and 10974052)the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20060542002)
文摘The spin-dependent conductance and magnetoresistance ratio (MRR) for a semiconductor heterostructures consisting of two magnetic barriers with different height and space have been investigated by the transfer-matrix method. It is shown that the splitting of the conductance for parallel and antiparallel magnetization configurations results in tremendous spin-dependent MRR, and the maximal MRRs reach 5300% and 3800% for the magnetic barrier spaces W = 81.3 and 243.9 nm, respectively. The obtained spin-filtering transport property of nanostructures with magnetic barriers may be useful to magnetic-barrier-based spintronics.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61274101,51362031,and 11675023)the Innovation Development Fund of China Academy of Engineering Physics(CAEP)(Grant No.ZYCX1921-02)+2 种基金the Presidential Foundation of CAEP(Grant No.YZ2015014)the Initial Project of University of Electronic Science and Technology of China,Zhongshan Institute(Grant No.415YKQ02)Science and Technology Bureau of Zhongshan,China(Grant Nos.417S26 and 180809162197886)
文摘We study the spin-dependent thermopower in a double-quantum-dot(DQD) embedded between the left and right two-dimensional electron gases(2DEGs) in doped quantum wells under an in-plane magnetic field. When the separation between the DQD is smaller than the Fermi wavelength in the 2DEGs, the asymmetry in the dots' energy levels leads to pronounced quantum interference effects characterized by the Dicke line-shape of the conductance, which are sensitive to the properties of the 2DEGs. The magnitude of the thermopower, which denotes the generated voltage in response to an infinitesimal temperature difference between the two 2DEGs under vanishing charge current, will be obviously enhanced by the Dicke effect. The application of the in-plane magnetic field results in the polarization of the spin-up and spin-down conductances and thermopowers, and enables an efficient spin-filter device in addition to a tunable pure spin thermopower in the absence of its charge counterpart.
基金Project supported by the National Natural Science Foundation of China (10774040)Excellent Young Scientist Foundation of Hubei Province (2006ABB032)
文摘Oxygen deficient Nd0.67Sr0.33MnO3-δ ceramic samples were prepared using conventional ceramic technology. A colossal electroresistance (CER) effect was found in Nd0.67Sr0.33MnO3-δ series. The electrical transport is magnetically coupled and spin-dependent over grain or phase boundaries. Electrical-field-induced changes of the spin array orientations inside of and between the magnetic domains by grain or phase boundaries have to be concluded for the strong electroresistive effect in Nd0.67Sr0.33MnO3-δ series.
基金Project supported by the National Natural Science Foundation of China(Grant No.11274378)the Key Research Program of the Chinese Academy of Sciences(Grant No.XDPB08-3)the MOST of China(Grant No.2013CB933401)
文摘It is commonly known that the hydrodynamic equations can be derived from the Boltzmann equation. In this paper, we derive similar spin-dependent balance equations based on the spinor Boltzmann equation. Besides the usual charge current, heat current, and pressure tensor, we also explore the characteristic spin accumulation and spin current as well as the spin-dependent pressure tensor and heat current in spintronics. The numerical results of these physical quantities are demonstrated using an example of spin-polarized transport through a mesoscopic ferromagnet.
基金supported by the National Natural Science Foundation of China(Grant Nos.11374266 and 11174253)the Program for New Century Excellent Talents in University,China
文摘We investigate a one-dimensional two-component system in an optical lattice of attractive interactions under a spin- dependent external potential. Based on the density-matrix renormalization group methods, we obtain its phase diagram as a function of the external potential imbalance and the strength of the attractive interaction through the analysis on the density profiles and the momentum pair correlation functions. We find that there are three different phases in the system, a coexisted fully polarized and Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) phase, a normal polarized phase, and a Bardeen- Cooper-Schrieffer (BCS) phase. Different from the systems of spin-independent external potential, where the FFLO phase is normally favored by the attractive interactions, in the present situation, the FFLO phases are easily destroyed by the attractive interactions, leading to the normal polarized or the BCS phase.
基金the Science Foundation of Civil Aviation Flight University of China(Grant No.JG2019-19)。
文摘We present a phase-and spin-dependent manipulation of leakage of a Majorana mode into a double quantum dot.We study the density of states(DOS)to show the effect of phase change factor on the Majorana leakage into(out)of a double quantum dot.The DOS is derived from the Green's function of the quantum dot by the equation of motion method,and exhibits a formant structure whenφ=0,2πand a resonance shape whenφ=0.5πand 1.5π.Also,it changes more strongly under the spin-polarized coefficient than the non-polarized lead.Such a theoretical model can be modified to explore the spin-dependent effect in the hybrid Majorana quantum dot system.
文摘Spin-polarized transport through a precessing magnetic spin coupled to ferromagnetic electrodes is studied using a non-equilibrium Green's function approach. The characteristic of conductance is obtained at zero temperature. We find that competition between spin-exchange interaction on the spin site and spin-orbit interaction in the barriers dominates the resonant behavior of conductance. In a parallel configuration, conductance peaks have identical amplitude. With the angle θ increasing, the width of resonant peaks is broadened or narrowed for different spin coherent states. In an anti-parallel case, spin-flip tunneling in the barriers will essentially enhance amplitude of the conductance peak.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11404013,11605003,61405003,11174020 and 11474012the Scientific Research Project of Beijing Educational Committee under Grant No KM201510011002the 2016 Graduate Research Program of Beijing Technology and Business University
文摘The extra heat generation in spin transport is usually interpreted in terms of the spin relaxation. Reformulating the heat generation rate, we find alternative current-force pairs without cross effects, which enable us to interpret the product of each pair as a distinct mechanism of heat generation. The results show that the spin-dependent part of the heat generation includes two terms. One is proportional to the square of the spin accumulation and arises from the spin relaxation. However, the other is proportional to the square of the spin-accumulation gradient and should be attributed to another mechanism, the spin diffusion. We illustrate the characteristics of the two mechanisms in a typical spin valve with a finite nonmagnetic spacer layer.
文摘Method is developed for self-consistent calculation of the energy spectrum of free energy and electrical disordered crystals. Processes of electron scattering on the ionic core potential of different sort, fluctuations of charge, spin density and lattice vibrations are taken into account. Electronic states of the system are described using tight binding multiband model. The nature of the spin-dependent electron transport of carbon nanotubes with chromium atoms adsorbed on the surface is explained. The value of the spin polarization of electron transport is determined by the difference of the partial densities of states of electrons with opposite spin projection at the Fermi level and the difference between the relaxation times of electron states. The value of the spin polarization of the electric current increases with increasing of Cr atoms concentration and magnitude of the external magnetic field.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.21673296 and 11334014)the Science and Technology Plan of Hunan Province,China(Grant No.2015RS4002)the Postdoctoral Science Foundation of Central South University,China
文摘By employing non-equilibrium Green's function combined with the spin-polarized density-functional theory, we investigate the spin-dependent electronic transport properties of armchair arsenene nanoribbons(a As NRs). Our results show that the spin-metal and spin-semiconductor properties can be observed in a As NRs with different widths. We also find that there is nearly 100% bipolar spin-filtering behavior in the a As NR-based device with antiparallel spin configuration. Moreover, rectifying behavior and giant magnetoresistance are found in the device. The corresponding physical analyses have been given.
基金This work was supported by the National Natural Science Foundation of China (Grant Nos. 11704118, 11774085, and 11404230), the Scientific Research Fund of Hu- nan Provincial Education Department (Grant Nos. 17A193 and17C0946), the Hunan Provincial Natural Science Foundation of China (Grant No. 2017JJ3210), and the Foundation of Science and Technology Bureau of Sichuan Province (No. 2013JY0085).
文摘Using the nonequilibrium Green's function method combined with the tight-binding Hamiltonian, we theoretically investigate the spin-dependent transmission probability and spin Seebeck coefficient of a crossed armchair-edge graphene nanoribbon (AGNR) superl'attice p-n junction under a perpendicular magnetic field with a ferromagnetic insulator, where junction widths Wi of 40 and 41 are considered to exemplify the effect of semiconducting and metallic AGNRs, respectively. A pristine AGNR system is metallic when the transverse layer m = 3j + 2 with a positive integer j and an insulator otherwise. When stubs are present, a semiconducting AGNR junction with width W1= 40 always shows metallic behavior regardless of the potential drop magnitude, magnetization strength, stub length, and per- pendicular magnetic field strength. However, metallic or semiconducting behavior can be obtained from a metallic AGNR junction with Wi = 41 by adjusting these physical parameters. Furthermore, a metal-to-semiconductor transition can be obtained for both superlattice p-n junctions by adjust- ing the number of periods of the superlattice. In addition, the spin-dependent Seebeck coefficient and spin Seebeck coefficient of the two systems are of the same order of magnitude owing to the appearance of a transmission gap, and the maximum absolute value of the spin Seebeck coefficient reaches 370 μV/K when the optimized parameters are used. The calculated results offer new possi- bilities for designing electronic or heat-spintronic nanodevices based on the graphene superlattice p-n junction.
基金supported by the National Natural Science Foundation of China(Grant No.11091240226)
文摘We propose to use Bloch oscillation of ultra-cold atoms in a spin-dependent optical lattice to prepare Schro¨dinger cat states.Depending on its internal state,an atom feels different periodic potentials and thus has different energy band structures for its center-of-mass motion.Consequently,under the same gravity force,the wave packets associated with different internal states perform Bloch oscillation of different amplitudes in space and in particular they can be macroscopically displaced with respect to each other.In this manner,a cat state can be prepared.
文摘Effects of soft-magnetic MnZn ferrite (Mn0.5Zn0.5Fe2O4, MZF) and hard-magnetic Ba ferrite (BaO.6Fe2O3, BaM) on the structure and magnetic transport properties of [La2/3Srl/3MnO3] (LSMO)/(x) [ferrites] (ferrites=MZF, BaM) composites have been investigated. It was found that the inclusion of MZF phase reduces magnetization and ferromagnetic-paramagnetic transition temperature (To) of the composites. With increasing the content of the dopants, the high-temperature magnetoresistance (MR) decreases, whereas low-temperature MR increases and reaches 42% at 150 K and x=0.1. However, for the LSMO/BaM composites, magnetization and ferromagneticparamagnetic transition temperature (To) decrease firstly as x〈5%, and then increase as x〉5%. The resistivity of the composites increases by five orders of magnitude at x=1% and is out of measured range at x=5%. High magnetic field has little effect on the resistivity and magnetoresistance originate from the pinning effect of BaM for the composites with x〉5%, which may grains.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61664008 and 11604286)the Scientific Technological Innovation Team of Yan’an City,China(Grant No.2017CXTD-01)
文摘The spin-dependent electronic transport properties of a zigzag zinc oxide(ZnO) nanoribbon are studied by using density functional theory with non-equilibrium Green's functions. We calculate the spin-polarized band structure, projected density of states, Bloch states, and transmission spectrum of the ZnO nanoribbon. It is determined that all Bloch states are located at the edge of the ZnO nanoribbon. The spin-up transmission eigenchannels are contributed from Zn 4s orbital,whereas the spin-down transmission eigenchannels are contributed from Zn 4s and O 2p orbitals. By analyzing the current-voltage curves for the opposite spins of the ZnO nanoribbon device, negative differential resistance(NDR) and spin filter effect are observed. Moreover, by constructing the ZnO nanoribbon modified by the Zn-edge defect, the spin-up current is severely suppressed because of the destruction of the spin-up transmission eigenchannels. However, the spin-down current is preserved, thus resulting in the perfect spin filter effect. Our results indicate that the ZnO nanoribbon modulated by the edge defect is a practical design for a spin filter.
基金the National Natural Science Foundation of China(Grant Nos.11974217 and 11874242)the Natural Science Foundation of Shandong Province,China(Grant No.ZR2018MA037)。
文摘Using the first-principles method,the spin-dependent transport properties of a novel platform molecule containing a freestanding molecular wire is investigated by simulating the spin-polarized scanning tunneling microscope experiment with Ni tip and Au substrate electrodes.Transport calculations show that the total current increases as the tip gradually approaches to the substrate,which is consistent with the conductance obtained from previous experiment.More interestingly,the spin polarization(SP)of current modulated by compression effect has the completely opposite trend to the total current.Transmission analyses reveal that the reduction of SP of current with compression process originates from the promotion of spin-down electron channel,which is controlled by deforming the molecule wire.In addition,the density of states shows that the SP of current is directly affected by the organic–ferromagnetic spinterface.The weak orbital hybridization between the Ni tip and propynyl of molecule results in high interfacial SP,whereas the breaking of the C≡C triple of propynyl in favor of the Ni–C–C bond induces the strong orbital hybridization and restrains the interfacial SP.This work proposes a new way to control and design the SP of current through organic–ferromagnetic spinterface using functional molecular platform.
基金supported by the Scientific Research Fund of Heilongjiang Provincial Education Department of China (GrantNo. 11551145)
文摘Based on the Green's function technique and the equation of motion approach, this paper theoretically studies the thermoelectric effect in parallel coupled double quantum dots (DQDs), in which Rashba spin-orbit interaction is taken into account. Rashba spin^rbit interaction contributions, even in a magnetic field, are exhibited obviously in the double quantum dots system for the thermoelectric effect. The periodic oscillation of thermopower can be controlled by tunning the Rashba spin^rbit interaction induced phase. The interesting spin-dependent thermoelectric effects will arise which has important influence on thermoelectric properties of the studied system.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11705097,11504178,and 11804158)the Natural Science Foundation of Jiangsu Province,China(Grant No.BK20170895)the Funding of Jiangsu Innovation Program for Graduate Education(Grant No.KYCX21_0709)
文摘Controlling the spin transport at the single-molecule level,especially without the use of ferromagnetic contacts,becomes a focus of research in spintronics.Inspired by the progress on atomic-level molecular synthesis,through firstprinciples calculations,we investigate the spin-dependent electronic transport of graphene nanoflakes with side-bonded functional groups,contacted by atomic carbon chain electrodes.It is found that,by rotating the functional group,the spin polarization of the transmission at the Fermi level could be switched between completely polarized and unpolarized states.Moreover,the transition between spin-up and spin-down polarized states can also be achieved,operating as a dual-spin filter.Further analysis shows that,it is the spin-dependent shift of density of states,caused by the rotation,that triggers the shift of transmission peaks,and then results in the variation of spin polarization.Such a feature is found to be robust to the length of the nanoflake and the electrode material,showing great application potential.Those findings may throw light on the development of spintronic devices.
基金Project supported by the Natural Science Foundation of Shandong Province,China(Grant No.ZR2021MA059)the Major Scientific and Technological Innovation Project(MSTIP)of Shandong Province,China(Grant No.2019JZZY010209)。
文摘Based on the density functional theory combined with the nonequilibrium Green function methodology,we have studied the thermally-driven spin-dependent transport properties of a combinational molecular junction consisting of a planar four-coordinate Fe molecule and a 15,16-dinitrile dihydropyrene/cyclophanediene molecule,with single-walled carbon nanotube bridge and electrode.Our results show that the magnetic field and light can effectively regulate the thermallydriven spin-dependent currents.Perfect thermal spin-filtering effect and good thermal switching effect are realized.The results are explained by the Fermi-Dirac distribution function,the spin-resolved transmission spectra,the spatial distribution of molecular projected self-consistent Hamiltonian orbitals,and the spin-resolved current spectra.On the basis of these thermally-driven spin-dependent transport properties,we have further designed three basic thermal spin molecular AND,OR,and NOT gates.
基金supported by the National Natural Science Foundation of China (Grant No. 11404322)the Natural Science Foundation of the Jiangsu Higher Education Institutions of China (Grant No. 18KJD140005)+1 种基金supported by the China Postdoctoral Science Foundation (Grant No. 2013M541635)the Postdoctoral Science Foundation of Jiangsu Province,China (Grant No. 1301018B)。
文摘A bias-controlled spin-filter and spin memory is theoretically proposed, which consists of the junction with a singlemolecule magnet sandwiched between the nonmagnetic and ferromagnetic(FM) leads. By applying different voltage pulses Vwriteacross the junction, the spin direction of the single-molecule magnet can be controlled to be parallel or anti-parallel to the magnetization of the FM lead, and the spin direction of SMM can be "read out" either by the magneto-resistance or by the spin current with another series of small voltage pulses V_(probe). It is shown that the polarization of the spin current is extremely high(up to 100%) and can be manipulated by the full-electric manner. This device scheme can be compatible with current technologies and has potential applications in high-density memory devices.
文摘The Einstein-Podolsky-Rosen paradox is resolved dynamically by using spin-dependent quantum trajectories inferred from Dirac’s equation for a relativistic electron. The theory provides a practical computational methodology for studying entanglement versus disentanglement for realistic Hamiltonians.