Magnon spin currents in insulating magnets are useful for low-power spintronics. However, in magnets stacked by antiferromagnetic(AFM) exchange coupling, which have recently aroused significant interest for potential ...Magnon spin currents in insulating magnets are useful for low-power spintronics. However, in magnets stacked by antiferromagnetic(AFM) exchange coupling, which have recently aroused significant interest for potential applications in spintronics, Bose–Einstein distribution populates magnon states across all energies from opposite eigenmodes, and hence the magnon spin current is largely compensated. Contrary to this common observation,here, we show that magnets with X-type AFM stacking, where opposite magnetic sublattices form orthogonal intersecting chains, support giant magnon spin currents with minimal compensation. Our model Hamiltonian calculations predict magnetic chain locking of magnon spin currents in these X-type magnets, significantly reducing their compensation ratio. In addition, the one-dimensional nature of the chain-like magnetic sublattices enhances magnon spin conductivities surpassing those of two-dimensional ferromagnets and canonical altermagnets. Notably, uncompensated X-type magnets, such as odd-layer antiferromagnets and ferrimagnets, can exhibit magnon spin currents polarized opposite to those expected by their net magnetization. These unprecedented properties of X-type magnets, combined with their inherent advantages resulting from AFM coupling, offer a promising new path for low-power high-performance spintronics.展开更多
Single shot all-optical switching of the magnetization by femtosecond laser pulses in rare-earth transition-metal ferrimagnetic materials is particularly promising for future ultrafast magnetic storage applications.Mo...Single shot all-optical switching of the magnetization by femtosecond laser pulses in rare-earth transition-metal ferrimagnetic materials is particularly promising for future ultrafast magnetic storage applications.Moreover,ultrafast lasergenerated spin currents appear to play an important role in the switching process.Here,we try to separately detect the spin current from Gd in a Co/Gd bilayer system using terahertz time-domain spectroscopy.To this aim,we use different capping,buffer and embedded layers in order to tune the spin-to-charge and spin-current propagation and identify currents from each of the layers.We attribute the observed THz emission in all layers to the transition metal demagnetization induced spin currents,and detect no contribution from the Gd demagnetization.We attribute this absence of Gd-induced THz signal to the potentially slow demagnetization of Gd,which shift the emission spectra to lower frequencies,below our detection capabilities.These results highlight the limitations in using materials suffering from the so-called critical slowdown for the optimization of spintronic THz emitters.展开更多
Using the perturbation method, we theoretically study the spin current and its heat effect in a multichannel quantum wire with Rashba spin-orbit coupling. The heat generated by the spin current is calculated. With the...Using the perturbation method, we theoretically study the spin current and its heat effect in a multichannel quantum wire with Rashba spin-orbit coupling. The heat generated by the spin current is calculated. With the increase of the width of the quantum wire, the spin current and the heat generated both exhibit period oscillations with equal amplitudes. When the quantum-channel number is doubled, the oscillation periods of the spin current and of the heat generated both decrease by a factor of 2. For the spin current js,xy, the amplitude increases with the decrease of the quantum channel; while the amplitude of the spin current js,yx remains the same. Therefore we conclude that the effect of the quantum-channel number on the spin current js,xy is greater than that on the spin current js,yx. The strength of the Rashba spin-orbit coupling is tunable by the gate voltage, and the gate voltage can be varied experimentally, which implies a new method of detecting the. spin current. In addition, we can control the amplitude and the oscillation period of the spin current by controlling the number of the quantum channels. All these characteristics of the spin current will be very important for detecting and controlling the spin current, and especially for designing new spintronic devices in the future.展开更多
Spin pumping in yttrium-iron-garnet（YIG）/nonmagnetic-metal（NM） layer systems under ferromagnetic resonance（FMR） conditions is a popular method of generating spin current in the NM layer.A good understanding of t...Spin pumping in yttrium-iron-garnet（YIG）/nonmagnetic-metal（NM） layer systems under ferromagnetic resonance（FMR） conditions is a popular method of generating spin current in the NM layer.A good understanding of the spin current source is essential in extracting spin Hall angle of the NM and in potential spintronics applications.It is widely believed that spin current is pumped from precessing YIG magnetization into NM layer.Here,by combining microwave absorption and DC-voltage measurements on thin YIG/Pt and YIG/NM_1/NM_2（NM_1 =Cu or Al,NM_2 =Pt or Ta）,we unambiguously showed that spin current in NM,instead of from the precessing YIG magnetization,came from the magnetized NM surface（in contact with thin YIG）,either due to the magnetic proximity effect（MPE） or from the inevitable diffused Fe ions from YIG to NM.This conclusion is reached through analyzing the FMR microwave absorption peaks with the DC-voltage peak from the inverse spin Hall effect（ISHE）.The voltage signal is attributed to the magnetized NM surface,hardly observed in the conventional FMR experiments,and was greatly amplified when the electrical detection circuit was switched on.展开更多
The spin transparency at the normal/ferromagnetic metal （NM/FM） interface was studied in PffYIG/Cu/FM multilayers. The spin current generated by the spin Hall effect （SHE） in Pt flows into Cu/FM due to magnetic in...The spin transparency at the normal/ferromagnetic metal （NM/FM） interface was studied in PffYIG/Cu/FM multilayers. The spin current generated by the spin Hall effect （SHE） in Pt flows into Cu/FM due to magnetic insulator YIG blocking charge current and transmitting spin current via the magnon current. Therefore, the nonlocal voltage induced by an inverse spin Hall effect （ISHE） in FM can be detected. With the magnetization of FM parallel or antiparallel to the spin polarization of pure spin currents （σsc）, the spin-independent nonlocal voltage is induced. This indicates that the spin transparency at the Cu/FM interface is spin-independent, which demonstrates that the influence of spin-dependent electro-chemical potential due to spin accumulation on the interfacial spin transparency is negligible. Furthermore, a larger spin Hall angle of Fe20Ni80 （Py） than that of Ni is obtained from the nonlocal voltage measurements.展开更多
This paper theoretically studies Josephson spin current through triplet superconductor/ferromagnet/triplet super- conductor junctions. At the ferromagnet/superconductor interfaces, the ferromagnetic scattering potenti...This paper theoretically studies Josephson spin current through triplet superconductor/ferromagnet/triplet super- conductor junctions. At the ferromagnet/superconductor interfaces, the ferromagnetic scattering potential gives rise to coupling between the Andreev bound states and lifts their spin degeneracy. These spin-split Andreev states carry the Josephson spin current through the junctions. The generated spin supercurrent can be controlled by the magnetization of a ferromagnetic thin layer and bias voltage across the junctions.展开更多
This paper theoretically reports the nonlocal Andreev reflection and spin current in a normal metal-ferromagnetic metal-superconducting Aharonov-Bohm interferometer. It is found that the electronic current and spin cu...This paper theoretically reports the nonlocal Andreev reflection and spin current in a normal metal-ferromagnetic metal-superconducting Aharonov-Bohm interferometer. It is found that the electronic current and spin current are sensitive to systematic parameters, such as the gate voltage of quantum dots and the external magnetic flux. The electronic current in the normal metal lead results from two competing processes： quasiparticle transmission and nonlocal Andreev reflection. The appearance of zero spin-up electronic current （or spin-down electronic current） signals the existence of nonlocal Andreev reflection, and the presence of zero electronic current results in the appearance of pure spin current.展开更多
The spin current in a parabolically confined semiconductor hcterojunction quantum wire with Drcsselhaus spinorbit coupling is theoretically studied by using the perturbation method. The formulae of the elements for li...The spin current in a parabolically confined semiconductor hcterojunction quantum wire with Drcsselhaus spinorbit coupling is theoretically studied by using the perturbation method. The formulae of the elements for linear and angular spin current densities are derived by using the recent definition for spin current based on spin continuity equation. It is found that the spin current in this Dresselhaus spin-orbit coupling quantum wire is antisymmetrical, which is different from that in Rashba model due to the difference in symmetry between these two models. Some numerical examples for the result are also demonstrated and discussed.展开更多
The spin transport properties are theoretically investigated when a quantum dot(QD)is side-coupled to Majorana bound states(MBSs)driven by a symmetric dipolar spin battery.It is found that MBSs have a great effect on ...The spin transport properties are theoretically investigated when a quantum dot(QD)is side-coupled to Majorana bound states(MBSs)driven by a symmetric dipolar spin battery.It is found that MBSs have a great effect on spin transport properties.The peak-to-valley ratio of the spin current decreases as the coupling strength between the MBS and the QD increases.Moreover,a non-zero charge current with two resonance peaks appears in the system.In the extreme case where the dot-MBS coupling strength is strong enough,the spin current and the charge current are both constants in the non-resonance peak range.When considering the effect of the Zeeman energy,it is interesting that the resonance peak at the higher energy appears one shoulder.And the shoulder turns into a peak when the Zeeman energy is big enough.In addition,the coupling strength between the two MBSs weakens their effects on the currents of the system.These results are helpful for understanding the MBSs signature in the transport spectra.展开更多
We investigate quantum effects on a nonrelativistic neutral particle with a permanent magnetic dipole moment that interacts with an electric field.This neutral particle is also under the influence of a background that...We investigate quantum effects on a nonrelativistic neutral particle with a permanent magnetic dipole moment that interacts with an electric field.This neutral particle is also under the influence of a background that breaks the Lorentz symmetry.We focus on the Lorentz symmetry violation background determined by a space-like vector field.Then,we show that the effects of the violation of Lorentz symmetry can yield an attractive Coulomb-type potential.Furthermore,we obtain the bound state solutions to the SchrÖdinger–Pauli equation and show that the spectrum of energy is a function of the Aharonov–Casher geometric quantum phase.Finally,we discuss the arising of persistent spin currents.展开更多
We investigate theoretically the spin current in a quantum wire with weak Dresselhaus spin-orbit coupling connected to two normal conductors. Both the quantum wire and conductors are described by a hard-wall confining...We investigate theoretically the spin current in a quantum wire with weak Dresselhaus spin-orbit coupling connected to two normal conductors. Both the quantum wire and conductors are described by a hard-wall confining potential. Using the electron wave-functions in the quantum wire and a new definition of spin current, we have calculated the elements of linear spin current density j^Ts,xi and j^Ts,yi（i=x, y, z）. We find that the elements j^Ts,xx and j^Ts,yy have a antisymmetrical relation and the element j^Ts,yz has the same amount levelas j^Ts,xx and j^Ts,yy. We also find a net linear spin current density, which has peaks at the center of quantum wire. The net linear spin current can induce a linear electric field, which may imply a way of spin current detection.展开更多
We investigate alternating response of the spin current in a quantum dot system coupled to a normal metal electrode, to which an alternating driving voltage and a pumping rotating magnetic field are applied. The expre...We investigate alternating response of the spin current in a quantum dot system coupled to a normal metal electrode, to which an alternating driving voltage and a pumping rotating magnetic field are applied. The expression of the time-averaged spin current and its differential is obtained based on a non-equilibrium Green＇s function method. We find that for a given rotating frequency, the spin current increases rapidly and appears to have small steps when the driven frequency increases. As the driven frequency is further increasing, the spin current can be significantly enhanced and approaches a stable value. The photon-assisted processes bring about interesting features of spin current. The influence of the gate voltage and temperature on the spin current is examined in detail.展开更多
We develop a research of spin currents in a^(23)Na spinor Bose–Einstein condensate(BEC)by applying a magnetic field gradient.The spin current is successfully induced by the spin-dependent force arising from the magne...We develop a research of spin currents in a^(23)Na spinor Bose–Einstein condensate(BEC)by applying a magnetic field gradient.The spin current is successfully induced by the spin-dependent force arising from the magnetic field gradient.The dynamics of the spin components under the magnetic force is investigated.The study is promising to be extended to produce a longer spin-coherence and to enhance the sensitivity of the spin-mixing interferometry in a spinor BEC.展开更多
Owing to the bistable character of the single molecular magnet （SMM）, it can generate 100% spin-polarized currents even connected with normal （N） leads. In this work, we study the phonon-assisted spin current in N...Owing to the bistable character of the single molecular magnet （SMM）, it can generate 100% spin-polarized currents even connected with normal （N） leads. In this work, we study the phonon-assisted spin current in N- SMM-N systems. We mainly focus on the interplay of SMM＇s bistable character and electron-phonon coupling. It is found that when SMM is trapped in one of the lowest bistable states, it can generate phonon-assisted spin- polarized currents. At the up-spin transport channel, it is accompanied by a phonon-assisted up-spin current, while at the down-spin transport channel, it is accompanied by a phonon-assisted down-spin current.展开更多
The article presents the results of experimental studies of the physical mechanisms and magnetic switching dynamics of films with one or two magnetic nanolayers under an irradiation picosecond and femtosecond laser pu...The article presents the results of experimental studies of the physical mechanisms and magnetic switching dynamics of films with one or two magnetic nanolayers under an irradiation picosecond and femtosecond laser pulses and also the samples of data recording devices on the spin storage medium are described. The study used a film with perpendicular anisotropy （Tb22Co5Fe73/Pr6O11/Tb29Co5Fe76, Tb25Co5Fe70/Al2O3, Tb22Co5Fe73, Tb19Co5Fe76） and films planar single-axis magnetic anisotropy （Co80Fe20/Pr6O11/CO30Fe70）. The magnetic switching of magnetic layers under action the magnetic field of a spin current is the most important for practical use in elements of spintronic. The spin current can also be realized using short electrical pulses. On the basis of this mechanism, the high-speed recording of information on the spin carrier has been realized.展开更多
Spintronics is a new discipline focusing on the research and application of electronic spin properties. After the discovery of the giant magnetoresistance effect in 1988, spintronics has had a huge impact on scientifi...Spintronics is a new discipline focusing on the research and application of electronic spin properties. After the discovery of the giant magnetoresistance effect in 1988, spintronics has had a huge impact on scientific progress and related applications in the development of information technology. In recent decades, the main motivation in spintronics has been efficiently controlling local magnetization using electron flow or voltage rather than controlling the electron flow using magnetization. Using spin-orbit coupling in a material can convert a charge current into a pure spin current(a flow of spin momenta without a charge flow) and generate a spin-orbit torque on the adjacent ferromagnets. The ability of spintronic devices to utilize spin-orbit torques to manipulate the magnetization has resulted in large-scale developments such as magnetic random-access memories and has boosted the spintronic research area. Here in, we review the theoretical and experimental results that have established this subfield of spintronics. We introduce the concept of a pure spin current and spin-orbit torques within the experimental framework, and we review transport-, magnetization-dynamics-, and opticalbased measurements and link then to both phenomenological and microscopic theories of the effect. The focus is on the related progress reported from Chinese universities and institutes, and we specifically highlight the contributions made by Chinese researchers.展开更多
This paper shows that a substantial amount of dissipationless spin-Hall current contribution may exist in the extrinsic spin-Hall effect,which originates from the spin-orbit coupling induced by the applied external el...This paper shows that a substantial amount of dissipationless spin-Hall current contribution may exist in the extrinsic spin-Hall effect,which originates from the spin-orbit coupling induced by the applied external electric field itself that drives the extrinsic spin-Hall effect in a nonmagnetic semiconductor （or metal）.By assuming that the impurity density is in a moderate range such that the total scattering potential due to all randomly distributed impurities is a smooth function of the space coordinate,it is shown that this dissipationless contribution shall be of the same orders of magnitude as the usual extrinsic contribution from spin-orbit dependent impurity scatterings （or may even be larger than the latter one）.The theoretical results obtained are in good agreement with recent relevant experimental results.展开更多
We propose a four-terminal device consisting of two parallel quantum dots with Rashba spin-orbit interaction （RSOI）, coupled to two side superconductor leads and two common ferromagnetic leads, respectively. The two...We propose a four-terminal device consisting of two parallel quantum dots with Rashba spin-orbit interaction （RSOI）, coupled to two side superconductor leads and two common ferromagnetic leads, respectively. The two ferromagnetic leads and two quantum dots form a ring threaded by Aharonov-Bohm （AB） flux. This device possesses normal quasiparticle transmission between the two ferromagnetic leads, and normal and crossed Andreev reflections providing conductive holes. For the appropriate spin polarization of the ferromagnetic leads, RSOI and AB flux, the pure spin-up （or spin-down） current without net charge current in the right lead, which is due to the equal numbers of electrons and holes with the same spin-polarization moving along the same direction, can be obtained by adjusting the gate voltage, which may be used in practice as a pure spin-current injector.展开更多
Recently,the spin-orbit coupling and spin current in nanodevice have been investigated extensively.In this paper,we review the recent progresses in this field.We introduce the real space Hamiltonian and the second qua...Recently,the spin-orbit coupling and spin current in nanodevice have been investigated extensively.In this paper,we review the recent progresses in this field.We introduce the real space Hamiltonian and the second quantization Hamiltonian of a typical quantum transport mesoscopic device,metal-QD-metal configuration,containing the spin-orbit interaction,e-e interactions,and magnetic field.Some noteworthy effects(e.g.,the spin-polarized current,spin accumulation,persistent spin current) originated from the spin-orbit interaction are reviewed,and the electric field induced by spin-current is mentioned.Lastly,we introduce some unsolved problems and prospects in this field.展开更多
Single-particle sequential tunneling is studied through a negative-U center hybridized with a superconducting, a ferromagnetic, and a normal metal electrodes. In stark contrast to the case of positive U, the single-pa...Single-particle sequential tunneling is studied through a negative-U center hybridized with a superconducting, a ferromagnetic, and a normal metal electrodes. In stark contrast to the case of positive U, the single-particle tunneling in attractive charging energy is usually prohibited by ground states with electrons in pairs. We find a microscopic mechanism to induce single-particle sates from pair states. As a consequence, in the nonpolarized metal terminal a remarkable pure spin current with no charge currents survives over a wide range of gate- and bias- voltages, which is rather crucial for experimental observation and design of spintronic devices. In addition, a significant spin-filter effect is presented in certain bias regime.展开更多
基金supported by the National Key R&D Program of China (Grant No.2022YFA1403203)the National Natural Science Funds for Distinguished Young Scholar (Grant No.52325105)+2 种基金the National Natural Science Foundation of China (Grant Nos.12274411,12241405,52250418,and12404185)the Basic Research Program of the Chinese Academy of Sciences (CAS) Based on Major Scientific Infrastructures (Grant No.JZHKYPT-2021-08)the CAS Project for Young Scientists in Basic Research (Grant No.YSBR-084)。
文摘Magnon spin currents in insulating magnets are useful for low-power spintronics. However, in magnets stacked by antiferromagnetic(AFM) exchange coupling, which have recently aroused significant interest for potential applications in spintronics, Bose–Einstein distribution populates magnon states across all energies from opposite eigenmodes, and hence the magnon spin current is largely compensated. Contrary to this common observation,here, we show that magnets with X-type AFM stacking, where opposite magnetic sublattices form orthogonal intersecting chains, support giant magnon spin currents with minimal compensation. Our model Hamiltonian calculations predict magnetic chain locking of magnon spin currents in these X-type magnets, significantly reducing their compensation ratio. In addition, the one-dimensional nature of the chain-like magnetic sublattices enhances magnon spin conductivities surpassing those of two-dimensional ferromagnets and canonical altermagnets. Notably, uncompensated X-type magnets, such as odd-layer antiferromagnets and ferrimagnets, can exhibit magnon spin currents polarized opposite to those expected by their net magnetization. These unprecedented properties of X-type magnets, combined with their inherent advantages resulting from AFM coupling, offer a promising new path for low-power high-performance spintronics.
基金supported by the National Key Research and Development Program of China(Grant No.2023YFF0719200)the National Natural Science Foundation of China(Grant No.62105011)+3 种基金the French National Research Agency ANR through the UFO project(Grant No.ANR-20-CE090013)the SLAM project(Grant No.ANR-23-CE30-0047)the MAT-PULSE-Lorraine Universitéd’Excellence project(Grant No.ANR-15-IDEX-04-LUE)the France 2030 Government Grants PEPR Electronic EMCOM(Grant No.ANR-22-PEEL-0009)。
文摘Single shot all-optical switching of the magnetization by femtosecond laser pulses in rare-earth transition-metal ferrimagnetic materials is particularly promising for future ultrafast magnetic storage applications.Moreover,ultrafast lasergenerated spin currents appear to play an important role in the switching process.Here,we try to separately detect the spin current from Gd in a Co/Gd bilayer system using terahertz time-domain spectroscopy.To this aim,we use different capping,buffer and embedded layers in order to tune the spin-to-charge and spin-current propagation and identify currents from each of the layers.We attribute the observed THz emission in all layers to the transition metal demagnetization induced spin currents,and detect no contribution from the Gd demagnetization.We attribute this absence of Gd-induced THz signal to the potentially slow demagnetization of Gd,which shift the emission spectra to lower frequencies,below our detection capabilities.These results highlight the limitations in using materials suffering from the so-called critical slowdown for the optimization of spintronic THz emitters.
文摘Using the perturbation method, we theoretically study the spin current and its heat effect in a multichannel quantum wire with Rashba spin-orbit coupling. The heat generated by the spin current is calculated. With the increase of the width of the quantum wire, the spin current and the heat generated both exhibit period oscillations with equal amplitudes. When the quantum-channel number is doubled, the oscillation periods of the spin current and of the heat generated both decrease by a factor of 2. For the spin current js,xy, the amplitude increases with the decrease of the quantum channel; while the amplitude of the spin current js,yx remains the same. Therefore we conclude that the effect of the quantum-channel number on the spin current js,xy is greater than that on the spin current js,yx. The strength of the Rashba spin-orbit coupling is tunable by the gate voltage, and the gate voltage can be varied experimentally, which implies a new method of detecting the. spin current. In addition, we can control the amplitude and the oscillation period of the spin current by controlling the number of the quantum channels. All these characteristics of the spin current will be very important for detecting and controlling the spin current, and especially for designing new spintronic devices in the future.
基金Project supported by the National Basic Research Program of China(Grant Nos.2015CB921502 and 2013CB922303)the National Natural Science Foundation of China(Grant Nos.11474184,116627805,and 11504203)+2 种基金the 111 Project(Grant No.B13029)Zhang Yin and Wang Xiangrong were supported by the Hong Kong RGC Grants(Grant Nos.16301816 and 605413)Wu Yong and Jiang Yong were supported by the National Natural Science Foundation of China(Grant No.51501007)
文摘Spin pumping in yttrium-iron-garnet（YIG）/nonmagnetic-metal（NM） layer systems under ferromagnetic resonance（FMR） conditions is a popular method of generating spin current in the NM layer.A good understanding of the spin current source is essential in extracting spin Hall angle of the NM and in potential spintronics applications.It is widely believed that spin current is pumped from precessing YIG magnetization into NM layer.Here,by combining microwave absorption and DC-voltage measurements on thin YIG/Pt and YIG/NM_1/NM_2（NM_1 =Cu or Al,NM_2 =Pt or Ta）,we unambiguously showed that spin current in NM,instead of from the precessing YIG magnetization,came from the magnetized NM surface（in contact with thin YIG）,either due to the magnetic proximity effect（MPE） or from the inevitable diffused Fe ions from YIG to NM.This conclusion is reached through analyzing the FMR microwave absorption peaks with the DC-voltage peak from the inverse spin Hall effect（ISHE）.The voltage signal is attributed to the magnetized NM surface,hardly observed in the conventional FMR experiments,and was greatly amplified when the electrical detection circuit was switched on.
基金Project supported by the National Basic Research Program of China(Grant No.2015CB921502)the National Natural Science Foundation of China(Grant Nos.11474184 and 11627805)+1 种基金the 111 Project,China(Grant No.B13029)the Fundamental Research Funds of Shandong University,China
文摘The spin transparency at the normal/ferromagnetic metal （NM/FM） interface was studied in PffYIG/Cu/FM multilayers. The spin current generated by the spin Hall effect （SHE） in Pt flows into Cu/FM due to magnetic insulator YIG blocking charge current and transmitting spin current via the magnon current. Therefore, the nonlocal voltage induced by an inverse spin Hall effect （ISHE） in FM can be detected. With the magnetization of FM parallel or antiparallel to the spin polarization of pure spin currents （σsc）, the spin-independent nonlocal voltage is induced. This indicates that the spin transparency at the Cu/FM interface is spin-independent, which demonstrates that the influence of spin-dependent electro-chemical potential due to spin accumulation on the interfacial spin transparency is negligible. Furthermore, a larger spin Hall angle of Fe20Ni80 （Py） than that of Ni is obtained from the nonlocal voltage measurements.
文摘This paper theoretically studies Josephson spin current through triplet superconductor/ferromagnet/triplet super- conductor junctions. At the ferromagnet/superconductor interfaces, the ferromagnetic scattering potential gives rise to coupling between the Andreev bound states and lifts their spin degeneracy. These spin-split Andreev states carry the Josephson spin current through the junctions. The generated spin supercurrent can be controlled by the magnetization of a ferromagnetic thin layer and bias voltage across the junctions.
基金Project supported by the Special Funds of the National Natural Science Foundation of China (Grant Nos 10847133 and 10847132)the Natural Science Foundation of Education Bureau of Jiangsu Province,China (Grant No 08KJB140002)
文摘This paper theoretically reports the nonlocal Andreev reflection and spin current in a normal metal-ferromagnetic metal-superconducting Aharonov-Bohm interferometer. It is found that the electronic current and spin current are sensitive to systematic parameters, such as the gate voltage of quantum dots and the external magnetic flux. The electronic current in the normal metal lead results from two competing processes： quasiparticle transmission and nonlocal Andreev reflection. The appearance of zero spin-up electronic current （or spin-down electronic current） signals the existence of nonlocal Andreev reflection, and the presence of zero electronic current results in the appearance of pure spin current.
基金Project supported by the National Natural Science Foundation of China （Grant No 10574042） and the Scientific Research Fund of Hunan Provincial Education Department （Grant No 04A031）.
文摘The spin current in a parabolically confined semiconductor hcterojunction quantum wire with Drcsselhaus spinorbit coupling is theoretically studied by using the perturbation method. The formulae of the elements for linear and angular spin current densities are derived by using the recent definition for spin current based on spin continuity equation. It is found that the spin current in this Dresselhaus spin-orbit coupling quantum wire is antisymmetrical, which is different from that in Rashba model due to the difference in symmetry between these two models. Some numerical examples for the result are also demonstrated and discussed.
基金supported by Natural Science Fund for Colleges and Universities in Hebei Province,China(Grant No.ZD2017031)the Doctoral Initial Funding of Hebei University of Science and Technology(Grant No.1181291)。
文摘The spin transport properties are theoretically investigated when a quantum dot(QD)is side-coupled to Majorana bound states(MBSs)driven by a symmetric dipolar spin battery.It is found that MBSs have a great effect on spin transport properties.The peak-to-valley ratio of the spin current decreases as the coupling strength between the MBS and the QD increases.Moreover,a non-zero charge current with two resonance peaks appears in the system.In the extreme case where the dot-MBS coupling strength is strong enough,the spin current and the charge current are both constants in the non-resonance peak range.When considering the effect of the Zeeman energy,it is interesting that the resonance peak at the higher energy appears one shoulder.And the shoulder turns into a peak when the Zeeman energy is big enough.In addition,the coupling strength between the two MBSs weakens their effects on the currents of the system.These results are helpful for understanding the MBSs signature in the transport spectra.
基金CNPq(Conselho Nacional de Desenvolvimento Científico e Tecnológico—Brazil)for financial support。
文摘We investigate quantum effects on a nonrelativistic neutral particle with a permanent magnetic dipole moment that interacts with an electric field.This neutral particle is also under the influence of a background that breaks the Lorentz symmetry.We focus on the Lorentz symmetry violation background determined by a space-like vector field.Then,we show that the effects of the violation of Lorentz symmetry can yield an attractive Coulomb-type potential.Furthermore,we obtain the bound state solutions to the SchrÖdinger–Pauli equation and show that the spectrum of energy is a function of the Aharonov–Casher geometric quantum phase.Finally,we discuss the arising of persistent spin currents.
基金supported by the Specialized Research Fund for the Doctoral Program of Higher Education of China under Grant No.20060542002the Hunan Provincial Natural Science Foundation of China under Grant No.06JJ2097the Hunan College of Science and Technology Research Foundation of China under Grant No.07XKYTB001
文摘We investigate theoretically the spin current in a quantum wire with weak Dresselhaus spin-orbit coupling connected to two normal conductors. Both the quantum wire and conductors are described by a hard-wall confining potential. Using the electron wave-functions in the quantum wire and a new definition of spin current, we have calculated the elements of linear spin current density j^Ts,xi and j^Ts,yi（i=x, y, z）. We find that the elements j^Ts,xx and j^Ts,yy have a antisymmetrical relation and the element j^Ts,yz has the same amount levelas j^Ts,xx and j^Ts,yy. We also find a net linear spin current density, which has peaks at the center of quantum wire. The net linear spin current can induce a linear electric field, which may imply a way of spin current detection.
基金Project supported by the National Natural Science Foundation of China(Grant No.60671042)the Key Project of Shanghai Municipal Commission of Science and Technology(Grant No.06JC14032)
文摘We investigate alternating response of the spin current in a quantum dot system coupled to a normal metal electrode, to which an alternating driving voltage and a pumping rotating magnetic field are applied. The expression of the time-averaged spin current and its differential is obtained based on a non-equilibrium Green＇s function method. We find that for a given rotating frequency, the spin current increases rapidly and appears to have small steps when the driven frequency increases. As the driven frequency is further increasing, the spin current can be significantly enhanced and approaches a stable value. The photon-assisted processes bring about interesting features of spin current. The influence of the gate voltage and temperature on the spin current is examined in detail.
基金Project supported by the National Key R&D Program of China(Grant No.2017YFA0304203)the National Natural Science Foundation of China(Grant Nos.62020106014,62175140,61901249,92165106,12104276,and 62011530047)+4 种基金PCSIRT(Grant No.IRT17R70)the Educational Reform and Innovation Project of Higher Education in Shanxi Province,China(Grant Nos.Z20220001 and Z20220013)111 Project(Grant No.D18001)the Applied Basic Research Project of Shanxi Province(Grant Nos.201901D211191 and 201901D211188)the Shanxi 1331 KSC。
文摘We develop a research of spin currents in a^(23)Na spinor Bose–Einstein condensate(BEC)by applying a magnetic field gradient.The spin current is successfully induced by the spin-dependent force arising from the magnetic field gradient.The dynamics of the spin components under the magnetic force is investigated.The study is promising to be extended to produce a longer spin-coherence and to enhance the sensitivity of the spin-mixing interferometry in a spinor BEC.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11504210,11504211,11504212,11274207,11274208,11174115 and 11325417the Key Program of the Ministry of Education of China under Grant No 212018+2 种基金Shanxi Provincial Scientific and Technological Project(2015031002-2)Shanxi Provincial Natural Science Foundation under Grant Nos2013011007-2 and 2013021010-5Outstanding Innovative Teams of Higher Learning Institutions of Shanxi Province
文摘Owing to the bistable character of the single molecular magnet （SMM）, it can generate 100% spin-polarized currents even connected with normal （N） leads. In this work, we study the phonon-assisted spin current in N- SMM-N systems. We mainly focus on the interplay of SMM＇s bistable character and electron-phonon coupling. It is found that when SMM is trapped in one of the lowest bistable states, it can generate phonon-assisted spin- polarized currents. At the up-spin transport channel, it is accompanied by a phonon-assisted up-spin current, while at the down-spin transport channel, it is accompanied by a phonon-assisted down-spin current.
文摘The article presents the results of experimental studies of the physical mechanisms and magnetic switching dynamics of films with one or two magnetic nanolayers under an irradiation picosecond and femtosecond laser pulses and also the samples of data recording devices on the spin storage medium are described. The study used a film with perpendicular anisotropy （Tb22Co5Fe73/Pr6O11/Tb29Co5Fe76, Tb25Co5Fe70/Al2O3, Tb22Co5Fe73, Tb19Co5Fe76） and films planar single-axis magnetic anisotropy （Co80Fe20/Pr6O11/CO30Fe70）. The magnetic switching of magnetic layers under action the magnetic field of a spin current is the most important for practical use in elements of spintronic. The spin current can also be realized using short electrical pulses. On the basis of this mechanism, the high-speed recording of information on the spin carrier has been realized.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11674142,51771099,11429401,and 51471081)the Program for Changjiang Scholars and Innovative Research Team in University,China(Grant No.IRT-16R35)
文摘Spintronics is a new discipline focusing on the research and application of electronic spin properties. After the discovery of the giant magnetoresistance effect in 1988, spintronics has had a huge impact on scientific progress and related applications in the development of information technology. In recent decades, the main motivation in spintronics has been efficiently controlling local magnetization using electron flow or voltage rather than controlling the electron flow using magnetization. Using spin-orbit coupling in a material can convert a charge current into a pure spin current(a flow of spin momenta without a charge flow) and generate a spin-orbit torque on the adjacent ferromagnets. The ability of spintronic devices to utilize spin-orbit torques to manipulate the magnetization has resulted in large-scale developments such as magnetic random-access memories and has boosted the spintronic research area. Here in, we review the theoretical and experimental results that have established this subfield of spintronics. We introduce the concept of a pure spin current and spin-orbit torques within the experimental framework, and we review transport-, magnetization-dynamics-, and opticalbased measurements and link then to both phenomenological and microscopic theories of the effect. The focus is on the related progress reported from Chinese universities and institutes, and we specifically highlight the contributions made by Chinese researchers.
基金Project supported by the National Natural Science Foundation of China (Grant No 10874049)the State Key Program for Basic Research of China (Grant No 2007CB925204)the Natural Science Foundation of Guangdong Province of China (Grant No07005834)
文摘This paper shows that a substantial amount of dissipationless spin-Hall current contribution may exist in the extrinsic spin-Hall effect,which originates from the spin-orbit coupling induced by the applied external electric field itself that drives the extrinsic spin-Hall effect in a nonmagnetic semiconductor （or metal）.By assuming that the impurity density is in a moderate range such that the total scattering potential due to all randomly distributed impurities is a smooth function of the space coordinate,it is shown that this dissipationless contribution shall be of the same orders of magnitude as the usual extrinsic contribution from spin-orbit dependent impurity scatterings （or may even be larger than the latter one）.The theoretical results obtained are in good agreement with recent relevant experimental results.
基金supported by the National Natural Science Foundation of China (Grant Nos. 10775091,10774094,10974124,and 11047172)the Excellent Youth and Midlife Scientist Scientific Research Encouragement Foundation of Shandong Province,China(Grant No. BS2010DS006)the Doctor Research Startup Foundation of Linyi University,China (Grant No. BS201023)
文摘We propose a four-terminal device consisting of two parallel quantum dots with Rashba spin-orbit interaction （RSOI）, coupled to two side superconductor leads and two common ferromagnetic leads, respectively. The two ferromagnetic leads and two quantum dots form a ring threaded by Aharonov-Bohm （AB） flux. This device possesses normal quasiparticle transmission between the two ferromagnetic leads, and normal and crossed Andreev reflections providing conductive holes. For the appropriate spin polarization of the ferromagnetic leads, RSOI and AB flux, the pure spin-up （or spin-down） current without net charge current in the right lead, which is due to the equal numbers of electrons and holes with the same spin-polarization moving along the same direction, can be obtained by adjusting the gate voltage, which may be used in practice as a pure spin-current injector.
基金supported by China National Funds for Distinguished Young Scientists(Grant No.10525418)the National Natural Science Foundation of China(Grant Nos.10734110 and 11121063)the National Basic Research Program of China(Grant No.2012CB921303)
文摘Recently,the spin-orbit coupling and spin current in nanodevice have been investigated extensively.In this paper,we review the recent progresses in this field.We introduce the real space Hamiltonian and the second quantization Hamiltonian of a typical quantum transport mesoscopic device,metal-QD-metal configuration,containing the spin-orbit interaction,e-e interactions,and magnetic field.Some noteworthy effects(e.g.,the spin-polarized current,spin accumulation,persistent spin current) originated from the spin-orbit interaction are reviewed,and the electric field induced by spin-current is mentioned.Lastly,we introduce some unsolved problems and prospects in this field.
基金This work was supported by the Program for New Century Excellent Talents in University （NCET） of China （Grant No. NCET-10-0090）, the National Natural Science Foundation of China （Grant Nos. 11174088 and 11274124）, the State Key Program for Basic Researches of China （Grant Nos. 2006CB921803 and 2010CB923400）, the Program for Changjiang Scholars and Innovative Research Team in University （PCSIRT） （Grant No. IRT1243）, and the Natural Science Foundation of Guangdong Province of China （Grant No. S2012010010681）.
文摘Single-particle sequential tunneling is studied through a negative-U center hybridized with a superconducting, a ferromagnetic, and a normal metal electrodes. In stark contrast to the case of positive U, the single-particle tunneling in attractive charging energy is usually prohibited by ground states with electrons in pairs. We find a microscopic mechanism to induce single-particle sates from pair states. As a consequence, in the nonpolarized metal terminal a remarkable pure spin current with no charge currents survives over a wide range of gate- and bias- voltages, which is rather crucial for experimental observation and design of spintronic devices. In addition, a significant spin-filter effect is presented in certain bias regime.
