To enhance the efficiency of green energy harvesting and pollutant degradation,significant efforts are focused on identifying highly effective catalysts.Metal-nitrogen-carbon single-atom catalysts(M-N-C SACs)have emer...To enhance the efficiency of green energy harvesting and pollutant degradation,significant efforts are focused on identifying highly effective catalysts.Metal-nitrogen-carbon single-atom catalysts(M-N-C SACs)have emerged as pivotal in catalysis due to their unique geometric structures,electronic states,and catalytic capabilities.Notably,the incorporation of magnetic elements at the active centers of these single-atom catalysts has garnered attention for their role in efficient electrochemical conversions.The orientation of spin states critically influences the adsorption and formation of reactants and intermediates,making the precise control of spin alignment and magnetic moments essential for reducing energy barriers and overcoming spin-related limitations,thereby enhancing catalytic activity.Thus,understanding the catalytic role of spin and modulating spin density at M-N-C single-atom centers holds profound fundamental and technological significance.In this review,we elucidate the fundamental mechanisms governing spin states and its influence in electrocatalysis.We then discuss various strategies for adjusting the spin states of active centers in the M-N-C SACs and the associated characterization techniques.Finally,we outline challenges and future perspectives of spin regulation for high-performance catalysts.This review provides deep insights into the micro-mechanisms of catalytic phenomena and offers a roadmap for designing spin-regulated catalysts for advanced energy applications.展开更多
Figure 6(a)in the paper[Chin.Phys.B 33074203(2024)]was incorrect due to editorial oversight.The correct figure is provided.This modification does not affect the result presented in the paper.
The development of magnetic heterostructures with strong perpendicular magnetic anisotropy(PMA),strong spin-orbit torques(SOTs),low impedance,and good integration compatibility at the same time is central for high-per...The development of magnetic heterostructures with strong perpendicular magnetic anisotropy(PMA),strong spin-orbit torques(SOTs),low impedance,and good integration compatibility at the same time is central for high-performance spintronic memory and computing applications.Here,we report the development of the PMA superlattice[Pt/Co/W]_(n)that can be sputtered-deposited on commercial oxidized silicon substrates and has giant SOTs,strong uniaxial PMA of≈9.2 Merg/cm^(3),and rigid macrospin performance.The damping-like and field-like SOTs of the[Pt/Co/W]_(n)superlattices exhibit a linear increase with the repeat number n and reach the giant values of 225%and-33%(two orders of magnitude greater than that in clean-limit Pt)at n=12,respectively.The damping-like SOT is also of the opposite sign and much greater in magnitude than the field-like SOT,regardless of the number n.These results clarify that the spin current that generates SOTs in the[Pt/Co/W]_(n)superlattices arises predominantly from the spin Hall effect rather than bulk Rashba spin splitting,providing a unified understanding of the SOTs in these superlattices.We also demonstrate deterministic switching in thickerthan-50-nm PMA[Pt/Co/W]_(12)superlattices at a low current density.This work establishes the[Pt/Co/W]_(n)superlattice as a compelling material candidate for ultra-fast,low-power,long-retention nonvolatile spintronic memory and computing technologies.展开更多
The thickness dependence of linearly polarized light-induced momentum anisotropy and the inverse spin Hall effect(PISHE)in topological insulator(TI)Bi_(2)Te_(3)films has been investigated.A significant enhancement of ...The thickness dependence of linearly polarized light-induced momentum anisotropy and the inverse spin Hall effect(PISHE)in topological insulator(TI)Bi_(2)Te_(3)films has been investigated.A significant enhancement of the PISHE signal is observed in the 12-quintuple-layer(QL)Bi_(2)Te_(3)film compared with that of the 3-and 5-QL samples,whereas a minimal value of photoinduced momentum anisotropy is found in the 12-QL sample.The photoinduced momentum anisotropy and the PISHE in Bi_(2)Te_(3)films are more than three and two orders of magnitude larger than those in Bi2Se3 films grown on SrTiO_(3)substrates,respectively.The 3-QL sample exhibits a sinusoidal dependence of the PISHE current on the light spot position,while the 5-QL and 12-QL samples show aW-shaped dependence,which arises from the different angles between the coordinate axis x and the in-plane crystallographic axis of the Bi_(2)Te_(3)films.Our findings demonstrate the critical role of film thickness in modulating both the photoinduced momentum anisotropy and the PISHE current,thereby suggesting a thickness-engineering strategy for designing novel optoelectronic devices based on TIs.展开更多
We consider matter-wave solitons in spin-orbit coupled Bose-Einstein condensates embedded in an optical lattice and study the dynamics of the soliton within the framework of Gross-Pitaevskii equations.We express spin ...We consider matter-wave solitons in spin-orbit coupled Bose-Einstein condensates embedded in an optical lattice and study the dynamics of the soliton within the framework of Gross-Pitaevskii equations.We express spin components of the soliton pair in terms of nonlinear Bloch equations and investigate the effective spin dynamics.It is seen that the effective magnetic field that appears in the Bloch equation is affected by optical lattices,and thus the optical lattice influences the precessional frequency of the spin components.We make use of numerical approaches to investigate the dynamical behavior of density profiles and center-of-mass of the soliton pair in the presence of the optical lattice.It is shown that the spin density is periodically varying due to flipping of spinors between the two states.The amplitude of spin-flipping oscillation increases with lattice strength.We find that the system can also exhibit interesting nonlinear behavior for chosen values of parameters.We present a fixed point analysis to study the effects of optical lattices on the nonlinear dynamics of the spin components.It is seen that the optical lattice can act as a control parameter to change the dynamical behavior of the spin components from periodic to chaotic.展开更多
Based on the relativistic hydrodynamic model of EM wave-spin plasmas interaction,the spin effects on the relativistic strong EM modes in magnetized plasma are investigated.The dispersion relations of the EM wave propa...Based on the relativistic hydrodynamic model of EM wave-spin plasmas interaction,the spin effects on the relativistic strong EM modes in magnetized plasma are investigated.The dispersion relations of the EM wave propagating parallel and perpendicular to the external magnetic field are obtained.Results show that the strong EM wave modes are affected by the time component of four-spin as well as the increase of electron effective mass.Especially in the case of EM wave propagating parallel to the external magnetic field,the time component of fourspin amplifies the influence of spin effects on the low-frequency modes obviously.展开更多
The present study pertains to the trilayer graphene in the presence of spin orbit coupling to probe the quantum spin/valley Hall effect. The spin Chern-number Cs for energy-bands of trilayer graphene having the essenc...The present study pertains to the trilayer graphene in the presence of spin orbit coupling to probe the quantum spin/valley Hall effect. The spin Chern-number Cs for energy-bands of trilayer graphene having the essence of intrinsic spin-orbit coupling is analytically calculated. We find that for each valley and spin, Cs is three times larger in trilayer graphene as compared to single layer graphene. Since the spin Chern-number corresponds to the number of edge states, consequently the trilayer graphene has edge states, three times more in comparison to single layer graphene. We also study the trilayer graphene in the presence of both electric-field and intrinsic spin-orbit coupling and investigate that the trilayer graphene goes through a phase transition from a quantum spin Hall state to a quantum valley Hall state when the strength of the electric field exceeds the intrinsic spin coupling strength. The robustness of the associated topological bulk-state of the trilayer graphene is evaluated by adding various perturbations such as Rashba spin-orbit （RSO） interaction αR, and exchange-magnetization M. In addition, we consider a theoretical model, where only one of the outer layers in trilayer graphene has the essence of intrinsic spin-orbit coupling, while the other two layers have zero intrinsic spin-orbit coupling. Although the first Chern number is non-zero for individual valleys of trilayer graphene in this model, however, we find that the system cannot be regarded as a topological insulator because the system as a whole is not gaped.展开更多
Based on the equations of state from the relativistic mean field theory without and with the inclusion of strangeness-bearing hyperons, we study the dimensionless spin parameter j = cJ/（GM2） of uniformly rotat- ing ...Based on the equations of state from the relativistic mean field theory without and with the inclusion of strangeness-bearing hyperons, we study the dimensionless spin parameter j = cJ/（GM2） of uniformly rotat- ing neutron stars. It is shown that the maximum value of the spin parameter jmax of a neutron star rotating at the Keplerian frequency fK is .jmax - 0.7 when the star mass M 〉 0.SM⊙, which is sustained for various versions of equations of state without and with hyperons. The relationship between j and the scaled rotation frequency f /fK is found to be insensitive to the star mass or the adopted equation of state in the models without hyperons. However, the emergence of byperons in neutron stars will lead to an uncertainty of the spin parameter j, which in turn could generate a complexity in the theoretical study of the quasi-periodic oscillations observed in disk-accreting compact-star systems.展开更多
Photonic spin Hall effect(PSHE), as a novel physical effect in light–matter interaction, provides an effective metrological method for characterizing the tiny variation in refractive index(RI). In this work, we propo...Photonic spin Hall effect(PSHE), as a novel physical effect in light–matter interaction, provides an effective metrological method for characterizing the tiny variation in refractive index(RI). In this work, we propose a multi-functional PSHE sensor based on VO_(2), a material that can reveal the phase transition behavior. By applying thermal control, the mutual transformation into different phase states of VO_(2) can be realized, which contributes to the flexible switching between multiple RI sensing tasks. When VO_(2) is insulating, the ultrasensitive detection of glucose concentrations in human blood is achieved. When VO_(2) is in a mixed phase, the structure can be designed to distinguish between the normal cells and cancer cells through no-label and real-time monitoring. When VO_(2) is metallic, the proposed PSHE sensor can act as an RI indicator for gas analytes. Compared with other multi-functional sensing devices with the complex structures, our design consists of only one analyte and two VO_(2) layers, which is very simple and elegant. Therefore, the proposed VO_(2)-based PSHE sensor has outstanding advantages such as small size, high sensitivity, no-label, and real-time detection, providing a new approach for investigating tunable multi-functional sensors.展开更多
Moleculardeviceswith highswitchingperformance and/or the perfect spin filtering effect have always been the pursuit with the development of molecular electronics.Hereb,yusingthe 2001.0V nonequilibrium.Green's func...Moleculardeviceswith highswitchingperformance and/or the perfect spin filtering effect have always been the pursuit with the development of molecular electronics.Hereb,yusingthe 2001.0V nonequilibrium.Green's function method in combination with the density functionaltheory,the switching performance and spin filtering properties of dimethyldihydropyrene(DHP)/cyclophanediene(CPD)photoswitchable molecule connected by carbon atomic chains(CACs)to two zigzag graphene nanoribbon electrodes have been theoretically investigated.The results show that DHP is more conductive than CPD and therefore an evident switching effect is demonstrated,and the switching ratio(RON/OFF)can reach 4.5×103.It is further revealed that the RoON/OF of DHP/CPD closely depends on the length of CACs.More specifically,the RoN/OFF values of DHP/CPD with odd-numbered CACs are larger than those with even-numbered CACs.More interestingly,a high or even perfect spin filtering effect can be obtained in these investigated DHP/CPD single-molecule devices.Our study is helpful for future design of single-molecule switches and spin filters and provides a way to optimize their performance by means of varying the length of bridging CACs.展开更多
Metal-based surface plasmon resonance(SPR)plays an important role in enhancing the photonic spin Hall effect(SHE)and developing sensitive optical sensors.However,the very large negative permittivities of metals limit ...Metal-based surface plasmon resonance(SPR)plays an important role in enhancing the photonic spin Hall effect(SHE)and developing sensitive optical sensors.However,the very large negative permittivities of metals limit their applications beyond the near-infrared regime.In this work,we theoretically present a new mechanism to enhance the photonic SHE by taking advantage of SiC-supported surface phonon resonance(SPhR)in the mid-infrared regime.The transverse displacement of photonic SHE is very sensitive to the wavelength of incident light and the thickness of SiC layer.Under the optimal parameter setup,the calculated largest transverse displacement of SiC-based SPhR structure reaches up to 163.8 ym,which is much larger than the condition of SPR.Moreover,an NO_(2) gas sensor based on the SPhR-enhanced photonic SHE is theoretically proposed with the superior sensing performance.Both the intensity and angle sensitivity of this sensor can be effectively manipulated by varying the damping rate of SiC.The results may provide a promising paradigm to enhance the photonic SHE in the mid-infrared region and open up new opportunity of highly sensitive refractive index sensors.展开更多
The spin superconductor state is the spin-polarized triplet exciton condensate,which can be viewed as a counterpart of the charge superconductor state.As an analogy of the charge Josephson effect,the spin Josephson ef...The spin superconductor state is the spin-polarized triplet exciton condensate,which can be viewed as a counterpart of the charge superconductor state.As an analogy of the charge Josephson effect,the spin Josephson effect can be generated in the spin superconductor/normal metal/spin superconductor junctions.Here we study the spin supercurrent in the Josephson junctions consisting of two spin superconductors with noncollinear spin polarizations.For the Josephson junctions with out-of-plane spin polarizations,the possibleπ-state spin supercurrent appears due to the Fermi momentum-splitting Andreev-like reflections at the normal metal/spin superconductor interfaces.For the Josephson junctions with in-plane spin polarizations,the anomalous spin supercurrent appears and is driven by the misorientation angle of the in-plane polarizations.The symmetry analysis shows that the appearance of the anomalous spin Josephson current is possible when the combined symmetry of the spin rotation and the time reversal is broken.展开更多
For the past few years,germanium-based semiconductor spintronics has attracted considerable interest due to its potential for integration into mainstream semiconductor technology.The main challenges in the development...For the past few years,germanium-based semiconductor spintronics has attracted considerable interest due to its potential for integration into mainstream semiconductor technology.The main challenges in the development of modern semiconductor spintronics are the generation,detection,and manipulation of spin currents.Here,the transport characteristics of a spin current generated by spin pumping through a GeBi semiconductor barrier in Y_(3)Fe_(5)O_(12)/GeBi/Pt heterostructures were investigated systematically.The effective spin-mixing conductance and inverse spin Hall voltage to quantitatively describe the spin transport characteristics were extracted.The spin-injection efficiency in the Y_(3)Fe_(5)O_(12)/GeBi/Pt heterostructures is comparable to that of the Y_(3)Fe_(5)O_(12)/Pt bilayer,and the inverse spin Hall voltage exponential decays with the increase in the barrier thickness.Furthermore,the band gap of the GeBi layer was tuned by changing the Bi content.The spin-injection efficiency at the YIG/semiconductor interface and the spin transportation within the semiconductor barrier are related to the band gap of the GeBi layer.Our results may be used as guidelines for the fabrication of efficient spin transmission structures and may lead to further studies on the impacts of different kinds of barrier materials.展开更多
The spin caloritronic properties of the Janus VSTe monolayer were investigated using density functional theory(DFT)and the non-equilibrium Green’s function(NEGF)method,implemented in the Atomistix Toolkit(ATK)package...The spin caloritronic properties of the Janus VSTe monolayer were investigated using density functional theory(DFT)and the non-equilibrium Green’s function(NEGF)method,implemented in the Atomistix Toolkit(ATK)package.Our study revealed significant spin-splitting within the Janus VSTe monolayer,which induced spin currents under a temperature gradient across the device.By applying a 1%tensile strain,the Janus VSTe monolayer exhibited a perfect thermal spin filtering effect(SFE),with the spin-up current nearly suppressed to zero.Both the unstrained and strained Janus VSTe monolayers demonstrated excellent spin caloritronic properties,with spin figures of merit of 10.915 and 8.432 at an average temperature of 100 K,respectively.Notably,these properties were found to be sensitive to temperature,performing optimally at lower temperatures.These results suggest a promising avenue for designing spin caloritronic devices aimed at efficient waste heat recovery.展开更多
Nano-ring-type magnetic tunnel junctions （NR-MTJs） with the layer structure of Ta（5）/Ir22Mn78（10）/ Co75Fe25（2）/Ru（0.75）/CoooFe20B20（3）/Al（0.6）-oxide/Co60Fe20B20（2.5）/Ta（3）/Ru（5） （thickness unit：...Nano-ring-type magnetic tunnel junctions （NR-MTJs） with the layer structure of Ta（5）/Ir22Mn78（10）/ Co75Fe25（2）/Ru（0.75）/CoooFe20B20（3）/Al（0.6）-oxide/Co60Fe20B20（2.5）/Ta（3）/Ru（5） （thickness unit： nm） were nano-fabricated on the Si（100）/SiO2 substrate using magnetron sputtering deposition combined with the optical lithography, electron beam lithography （EBL） and Ar ion-beam etching techniques. The smaller NR-MTJs with the inner- and outer-diameter of around 50 and 100 nm and also their corresponding NR-MTJ arrays were nano-patterned. The tunnelling magnetoresistance （TMR ＆ R） versus driving current （I） loops for a spin-polarized current switching were measured, and the TMR ratio of around 35% at room temperature were observed. The critical values of switching current for the free Co60Fe20B20 layer relative to the reference Co6oFe2oB2o layer between parallel and anti-parallel magnetization states were between 0.50 and 0.75 mA in such NR-MTJs. It is suggested that the applicable MRAM fabrication with the density and capacity higher than 256 Mbit/inch2 even 6 Gbite/inch2 are possible using both I NR-MTJ＋1 transistor structure and current switching mechanism based on based on our fabricated 4×4 MRAM demo devices.展开更多
The magnetic and electronic properties of the geometrically frustrated triangular antiferromagnet CuCrO2 are investigated by first principles through density functional theory calculations within the generalized gradi...The magnetic and electronic properties of the geometrically frustrated triangular antiferromagnet CuCrO2 are investigated by first principles through density functional theory calculations within the generalized gradient approxi- mations （GGA）＋U scheme. The spin exchange interactions up to the third nearest neighbours in the ab plane as well as the coupling between adjacent layers are calculated to examine the magnetism and spin frustration. It is found that CuCrO2 has a natural two-dimensional characteristic of the magnetic interaction. Using Monte Carlo simulation, we obtain the Neel temperature to be 29.9 K, which accords well with the experimental value of 24 K. Based on non- collinear magnetic structure calculations, we verify that the incommensurate spiral-spin structure with （110） spiral plane is believable for the magnetic ground state, which is consistent with the experimental observations. Due to intra-layer geometric spin frustration, parallel helical-spin chains arise along the a, b, or a＋ b directions, each with a screw-rotation angle of about I20°. Our calculations of the density of states show that the spin frustration plays an important role in the change of d-p hybridization, while the spin-orbit coupling has a very limited influence on the electronic structure.展开更多
We investigate the electron transport in silicene with both staggered electric potential and magnetization; the latter comes from the magnetic proximity effect by depositing silicene on a magnetic insulator. It is sho...We investigate the electron transport in silicene with both staggered electric potential and magnetization; the latter comes from the magnetic proximity effect by depositing silicene on a magnetic insulator. It is shown that the silicene could be a spin and valley half metal under appropriate parameters when the spin–orbit interaction is considered; further, the filtered spin and valley could be controlled by modulating the staggered potential or magnetization. It is also found that in the spin-valve structure of silicene, not only can the antiparallel magnetization configuration significantly reduce the valve-structure conductance, but the reversing staggered electric potential can cause a high-performance magnetoresistance due to the spin and valley blocking effects. Our findings show that the silicene might be an ideal basis for the spin and valley filter analyzer devices.展开更多
The realization of a perfect spin or valley filtering effect in two-dimensional graphene-like materials is one of the fundamental objectives in spintronics and valleytronics. For this purpose, we study spin- and valle...The realization of a perfect spin or valley filtering effect in two-dimensional graphene-like materials is one of the fundamental objectives in spintronics and valleytronics. For this purpose, we study spin- and valley-dependent transport in a silicene system with spatially alternative strains. It is found that due to the valley-opposite gauge field induced by the strain, the strained silicene with a superlattice structure exhibits an angle-resolved valley and spin filtering effect when the spin–orbit interaction is considered. When the interaction that breaks the time reversal symmetry is introduced, such as the spin or valley dependent staggered magnetization, the system is shown to be a perfect spin and valley half metal in which only one spin and valley species is allowed to transport. Our findings are helpful to design both spintronic and valleytronic devices based on silicene.展开更多
According to the general principle of non-equilibrium thermodynamics, we propose a set of macroscopic transport equations for the spin transport and the charge transport, In particular, the spin torque is introduced a...According to the general principle of non-equilibrium thermodynamics, we propose a set of macroscopic transport equations for the spin transport and the charge transport, In particular, the spin torque is introduced as a generalized ＇current density＇ to describe the phenomena associated with the spin non-conservation in a unified framework. The Einstein relations and the Onsager relations between different transport phenomena are established. Specifically, the spin transport properties of the isotropic non-magnetic and the isotropic magnetic two-dimensional electron gases are fully described by using this theory, in which only the macroscopic-spin-related transport phenomena allowed by the symmetry of the system are taken into account.展开更多
Topological insulators＇ properties and their potential device applications are reviewed. We also explain why topologi- cal insulator （TI） nanostructnres are an important avenue for research and discuss some methods...Topological insulators＇ properties and their potential device applications are reviewed. We also explain why topologi- cal insulator （TI） nanostructnres are an important avenue for research and discuss some methods by which TI nanostructures are produced and characterized. The rapid development of high-quality TI nanostructures provides an ideal platform to ex- ploit salient physical phenomena that have been theoretically predicted but not yet experimentally realized.展开更多
文摘To enhance the efficiency of green energy harvesting and pollutant degradation,significant efforts are focused on identifying highly effective catalysts.Metal-nitrogen-carbon single-atom catalysts(M-N-C SACs)have emerged as pivotal in catalysis due to their unique geometric structures,electronic states,and catalytic capabilities.Notably,the incorporation of magnetic elements at the active centers of these single-atom catalysts has garnered attention for their role in efficient electrochemical conversions.The orientation of spin states critically influences the adsorption and formation of reactants and intermediates,making the precise control of spin alignment and magnetic moments essential for reducing energy barriers and overcoming spin-related limitations,thereby enhancing catalytic activity.Thus,understanding the catalytic role of spin and modulating spin density at M-N-C single-atom centers holds profound fundamental and technological significance.In this review,we elucidate the fundamental mechanisms governing spin states and its influence in electrocatalysis.We then discuss various strategies for adjusting the spin states of active centers in the M-N-C SACs and the associated characterization techniques.Finally,we outline challenges and future perspectives of spin regulation for high-performance catalysts.This review provides deep insights into the micro-mechanisms of catalytic phenomena and offers a roadmap for designing spin-regulated catalysts for advanced energy applications.
文摘Figure 6(a)in the paper[Chin.Phys.B 33074203(2024)]was incorrect due to editorial oversight.The correct figure is provided.This modification does not affect the result presented in the paper.
基金supported by the National Key Research and Development Program of China(Grant No.2022YFA1204000)the Beijing National Natural Science Foundation(Grant No.Z230006)the National Natural Science Foundation of China(Grant Nos.12304155 and 12274405).
文摘The development of magnetic heterostructures with strong perpendicular magnetic anisotropy(PMA),strong spin-orbit torques(SOTs),low impedance,and good integration compatibility at the same time is central for high-performance spintronic memory and computing applications.Here,we report the development of the PMA superlattice[Pt/Co/W]_(n)that can be sputtered-deposited on commercial oxidized silicon substrates and has giant SOTs,strong uniaxial PMA of≈9.2 Merg/cm^(3),and rigid macrospin performance.The damping-like and field-like SOTs of the[Pt/Co/W]_(n)superlattices exhibit a linear increase with the repeat number n and reach the giant values of 225%and-33%(two orders of magnitude greater than that in clean-limit Pt)at n=12,respectively.The damping-like SOT is also of the opposite sign and much greater in magnitude than the field-like SOT,regardless of the number n.These results clarify that the spin current that generates SOTs in the[Pt/Co/W]_(n)superlattices arises predominantly from the spin Hall effect rather than bulk Rashba spin splitting,providing a unified understanding of the SOTs in these superlattices.We also demonstrate deterministic switching in thickerthan-50-nm PMA[Pt/Co/W]_(12)superlattices at a low current density.This work establishes the[Pt/Co/W]_(n)superlattice as a compelling material candidate for ultra-fast,low-power,long-retention nonvolatile spintronic memory and computing technologies.
基金supported by the National Natural Science Foundation of China(Grant Nos.62074036,61674038,and 11574302)the Foreign Cooperation Project of Fujian Province,China(Grant No.2023I0005)+2 种基金the Open Research Fund Program of the State Key Laboratory of Low Dimensional Quantum Physics(Grant No.KF202108)the National Key Research and Development Program of China(Grant No.2016YFB0402303)the Foundation of the Fujian Provincial Department of Industry and Information Technology of China(Grant No.82318075).
文摘The thickness dependence of linearly polarized light-induced momentum anisotropy and the inverse spin Hall effect(PISHE)in topological insulator(TI)Bi_(2)Te_(3)films has been investigated.A significant enhancement of the PISHE signal is observed in the 12-quintuple-layer(QL)Bi_(2)Te_(3)film compared with that of the 3-and 5-QL samples,whereas a minimal value of photoinduced momentum anisotropy is found in the 12-QL sample.The photoinduced momentum anisotropy and the PISHE in Bi_(2)Te_(3)films are more than three and two orders of magnitude larger than those in Bi2Se3 films grown on SrTiO_(3)substrates,respectively.The 3-QL sample exhibits a sinusoidal dependence of the PISHE current on the light spot position,while the 5-QL and 12-QL samples show aW-shaped dependence,which arises from the different angles between the coordinate axis x and the in-plane crystallographic axis of the Bi_(2)Te_(3)films.Our findings demonstrate the critical role of film thickness in modulating both the photoinduced momentum anisotropy and the PISHE current,thereby suggesting a thickness-engineering strategy for designing novel optoelectronic devices based on TIs.
文摘We consider matter-wave solitons in spin-orbit coupled Bose-Einstein condensates embedded in an optical lattice and study the dynamics of the soliton within the framework of Gross-Pitaevskii equations.We express spin components of the soliton pair in terms of nonlinear Bloch equations and investigate the effective spin dynamics.It is seen that the effective magnetic field that appears in the Bloch equation is affected by optical lattices,and thus the optical lattice influences the precessional frequency of the spin components.We make use of numerical approaches to investigate the dynamical behavior of density profiles and center-of-mass of the soliton pair in the presence of the optical lattice.It is shown that the spin density is periodically varying due to flipping of spinors between the two states.The amplitude of spin-flipping oscillation increases with lattice strength.We find that the system can also exhibit interesting nonlinear behavior for chosen values of parameters.We present a fixed point analysis to study the effects of optical lattices on the nonlinear dynamics of the spin components.It is seen that the optical lattice can act as a control parameter to change the dynamical behavior of the spin components from periodic to chaotic.
基金supported by the National Natural Science Foundation of China under Grant No.12065011the PhD Starting Fund program of TongRen University under Grant No.trxyDH2223
文摘Based on the relativistic hydrodynamic model of EM wave-spin plasmas interaction,the spin effects on the relativistic strong EM modes in magnetized plasma are investigated.The dispersion relations of the EM wave propagating parallel and perpendicular to the external magnetic field are obtained.Results show that the strong EM wave modes are affected by the time component of four-spin as well as the increase of electron effective mass.Especially in the case of EM wave propagating parallel to the external magnetic field,the time component of fourspin amplifies the influence of spin effects on the low-frequency modes obviously.
基金Majeed Ur Rehman acknowledges the support from the Chinese Academy of Sciences(CAS)and TWAS for his Ph.D.studies at the University of Science and Technology,China in the category of 2016 CAS-TWAS President’s Fellowship Awardee(Grant No.2016-156)
文摘The present study pertains to the trilayer graphene in the presence of spin orbit coupling to probe the quantum spin/valley Hall effect. The spin Chern-number Cs for energy-bands of trilayer graphene having the essence of intrinsic spin-orbit coupling is analytically calculated. We find that for each valley and spin, Cs is three times larger in trilayer graphene as compared to single layer graphene. Since the spin Chern-number corresponds to the number of edge states, consequently the trilayer graphene has edge states, three times more in comparison to single layer graphene. We also study the trilayer graphene in the presence of both electric-field and intrinsic spin-orbit coupling and investigate that the trilayer graphene goes through a phase transition from a quantum spin Hall state to a quantum valley Hall state when the strength of the electric field exceeds the intrinsic spin coupling strength. The robustness of the associated topological bulk-state of the trilayer graphene is evaluated by adding various perturbations such as Rashba spin-orbit （RSO） interaction αR, and exchange-magnetization M. In addition, we consider a theoretical model, where only one of the outer layers in trilayer graphene has the essence of intrinsic spin-orbit coupling, while the other two layers have zero intrinsic spin-orbit coupling. Although the first Chern number is non-zero for individual valleys of trilayer graphene in this model, however, we find that the system cannot be regarded as a topological insulator because the system as a whole is not gaped.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11175108,U1432119,1146114100,11205075,11375076 and 11475104the Shandong Natural Science Foundation under Grant No ZR2014AQ012the Foundation of Shandong University under Grant No 2015WHWLJH01
文摘Based on the equations of state from the relativistic mean field theory without and with the inclusion of strangeness-bearing hyperons, we study the dimensionless spin parameter j = cJ/（GM2） of uniformly rotat- ing neutron stars. It is shown that the maximum value of the spin parameter jmax of a neutron star rotating at the Keplerian frequency fK is .jmax - 0.7 when the star mass M 〉 0.SM⊙, which is sustained for various versions of equations of state without and with hyperons. The relationship between j and the scaled rotation frequency f /fK is found to be insensitive to the star mass or the adopted equation of state in the models without hyperons. However, the emergence of byperons in neutron stars will lead to an uncertainty of the spin parameter j, which in turn could generate a complexity in the theoretical study of the quasi-periodic oscillations observed in disk-accreting compact-star systems.
基金Project supported by the National Natural Science Foundation of China(Grant No.NSFC 12175107)the Natural Science Foundation of Nanjing Vocational University of Industry Technology,China(Grant No.YK22-02-08)+3 种基金the Qing Lan Project of Jiangsu Province,Chinathe Postgraduate Research&Practice Innovation Program of Jiangsu Province,China(Grant No.KYCX23_0964)the Natural Science Foundation of Jiangsu Province,China(Grant No.BK20230347)the Fund from the Research Center of Industrial Perception and Intelligent Manufacturing Equipment Engineering of Jiangsu Province,China(Grant No.ZK21-05-09)。
文摘Photonic spin Hall effect(PSHE), as a novel physical effect in light–matter interaction, provides an effective metrological method for characterizing the tiny variation in refractive index(RI). In this work, we propose a multi-functional PSHE sensor based on VO_(2), a material that can reveal the phase transition behavior. By applying thermal control, the mutual transformation into different phase states of VO_(2) can be realized, which contributes to the flexible switching between multiple RI sensing tasks. When VO_(2) is insulating, the ultrasensitive detection of glucose concentrations in human blood is achieved. When VO_(2) is in a mixed phase, the structure can be designed to distinguish between the normal cells and cancer cells through no-label and real-time monitoring. When VO_(2) is metallic, the proposed PSHE sensor can act as an RI indicator for gas analytes. Compared with other multi-functional sensing devices with the complex structures, our design consists of only one analyte and two VO_(2) layers, which is very simple and elegant. Therefore, the proposed VO_(2)-based PSHE sensor has outstanding advantages such as small size, high sensitivity, no-label, and real-time detection, providing a new approach for investigating tunable multi-functional sensors.
基金This work is supported by the National Natural Sci-ence Foundation China(No.22173052 of and No.11974217).
文摘Moleculardeviceswith highswitchingperformance and/or the perfect spin filtering effect have always been the pursuit with the development of molecular electronics.Hereb,yusingthe 2001.0V nonequilibrium.Green's function method in combination with the density functionaltheory,the switching performance and spin filtering properties of dimethyldihydropyrene(DHP)/cyclophanediene(CPD)photoswitchable molecule connected by carbon atomic chains(CACs)to two zigzag graphene nanoribbon electrodes have been theoretically investigated.The results show that DHP is more conductive than CPD and therefore an evident switching effect is demonstrated,and the switching ratio(RON/OFF)can reach 4.5×103.It is further revealed that the RoON/OF of DHP/CPD closely depends on the length of CACs.More specifically,the RoN/OFF values of DHP/CPD with odd-numbered CACs are larger than those with even-numbered CACs.More interestingly,a high or even perfect spin filtering effect can be obtained in these investigated DHP/CPD single-molecule devices.Our study is helpful for future design of single-molecule switches and spin filters and provides a way to optimize their performance by means of varying the length of bridging CACs.
基金Project supported by the National Natural Science Foundation of China (Grant No.12175107)the Natural Science Foundation of Nanjing Vocational University of Industry Technology (Grant No.YK22-02-08)+2 种基金the Qing Lan Project of Jiangsu Provincethe Natural Science Foundation of Jiangsu Province of China (Grant No.BK20230347)the Fund from the Research Center of Industrial Perception and Intelligent Manufacturing Equipment Engineering of Jiangsu Province,China (Grant No.ZK21-05-09)。
文摘Metal-based surface plasmon resonance(SPR)plays an important role in enhancing the photonic spin Hall effect(SHE)and developing sensitive optical sensors.However,the very large negative permittivities of metals limit their applications beyond the near-infrared regime.In this work,we theoretically present a new mechanism to enhance the photonic SHE by taking advantage of SiC-supported surface phonon resonance(SPhR)in the mid-infrared regime.The transverse displacement of photonic SHE is very sensitive to the wavelength of incident light and the thickness of SiC layer.Under the optimal parameter setup,the calculated largest transverse displacement of SiC-based SPhR structure reaches up to 163.8 ym,which is much larger than the condition of SPR.Moreover,an NO_(2) gas sensor based on the SPhR-enhanced photonic SHE is theoretically proposed with the superior sensing performance.Both the intensity and angle sensitivity of this sensor can be effectively manipulated by varying the damping rate of SiC.The results may provide a promising paradigm to enhance the photonic SHE in the mid-infrared region and open up new opportunity of highly sensitive refractive index sensors.
基金Project supported by the National Key R&D Program of China(Grant No.2022YFA1403601).
文摘The spin superconductor state is the spin-polarized triplet exciton condensate,which can be viewed as a counterpart of the charge superconductor state.As an analogy of the charge Josephson effect,the spin Josephson effect can be generated in the spin superconductor/normal metal/spin superconductor junctions.Here we study the spin supercurrent in the Josephson junctions consisting of two spin superconductors with noncollinear spin polarizations.For the Josephson junctions with out-of-plane spin polarizations,the possibleπ-state spin supercurrent appears due to the Fermi momentum-splitting Andreev-like reflections at the normal metal/spin superconductor interfaces.For the Josephson junctions with in-plane spin polarizations,the anomalous spin supercurrent appears and is driven by the misorientation angle of the in-plane polarizations.The symmetry analysis shows that the appearance of the anomalous spin Josephson current is possible when the combined symmetry of the spin rotation and the time reversal is broken.
基金Project supported by the National Key Research and Development Program of China(Grant No.2021YFA0718701)the China Postdoctoral Science Foundation(Grant No.2022M722888)the National Natural Science Foundation of China(Grant Nos.12174347 and 12004340).
文摘For the past few years,germanium-based semiconductor spintronics has attracted considerable interest due to its potential for integration into mainstream semiconductor technology.The main challenges in the development of modern semiconductor spintronics are the generation,detection,and manipulation of spin currents.Here,the transport characteristics of a spin current generated by spin pumping through a GeBi semiconductor barrier in Y_(3)Fe_(5)O_(12)/GeBi/Pt heterostructures were investigated systematically.The effective spin-mixing conductance and inverse spin Hall voltage to quantitatively describe the spin transport characteristics were extracted.The spin-injection efficiency in the Y_(3)Fe_(5)O_(12)/GeBi/Pt heterostructures is comparable to that of the Y_(3)Fe_(5)O_(12)/Pt bilayer,and the inverse spin Hall voltage exponential decays with the increase in the barrier thickness.Furthermore,the band gap of the GeBi layer was tuned by changing the Bi content.The spin-injection efficiency at the YIG/semiconductor interface and the spin transportation within the semiconductor barrier are related to the band gap of the GeBi layer.Our results may be used as guidelines for the fabrication of efficient spin transmission structures and may lead to further studies on the impacts of different kinds of barrier materials.
基金Project(2022JJ30049)supported by the Natural Science Foundation of Hunan Province,China。
文摘The spin caloritronic properties of the Janus VSTe monolayer were investigated using density functional theory(DFT)and the non-equilibrium Green’s function(NEGF)method,implemented in the Atomistix Toolkit(ATK)package.Our study revealed significant spin-splitting within the Janus VSTe monolayer,which induced spin currents under a temperature gradient across the device.By applying a 1%tensile strain,the Janus VSTe monolayer exhibited a perfect thermal spin filtering effect(SFE),with the spin-up current nearly suppressed to zero.Both the unstrained and strained Janus VSTe monolayers demonstrated excellent spin caloritronic properties,with spin figures of merit of 10.915 and 8.432 at an average temperature of 100 K,respectively.Notably,these properties were found to be sensitive to temperature,performing optimally at lower temperatures.These results suggest a promising avenue for designing spin caloritronic devices aimed at efficient waste heat recovery.
基金the State Key Project of Fundamental Research of Ministry of Science and Technology （No. 2006CB932200） the National Natural Science Foundation of China （NSFC, No. 10574156）+2 种基金 the Knowledge Innovation Program of Chinese Aca.demy of Sciencesthe protial support of 0utstanding Young Researcher Foundation （Nos. 50325104 and 50528101） K.C.Wong Education Foundation, Hong Kong.
文摘Nano-ring-type magnetic tunnel junctions （NR-MTJs） with the layer structure of Ta（5）/Ir22Mn78（10）/ Co75Fe25（2）/Ru（0.75）/CoooFe20B20（3）/Al（0.6）-oxide/Co60Fe20B20（2.5）/Ta（3）/Ru（5） （thickness unit： nm） were nano-fabricated on the Si（100）/SiO2 substrate using magnetron sputtering deposition combined with the optical lithography, electron beam lithography （EBL） and Ar ion-beam etching techniques. The smaller NR-MTJs with the inner- and outer-diameter of around 50 and 100 nm and also their corresponding NR-MTJ arrays were nano-patterned. The tunnelling magnetoresistance （TMR ＆ R） versus driving current （I） loops for a spin-polarized current switching were measured, and the TMR ratio of around 35% at room temperature were observed. The critical values of switching current for the free Co60Fe20B20 layer relative to the reference Co6oFe2oB2o layer between parallel and anti-parallel magnetization states were between 0.50 and 0.75 mA in such NR-MTJs. It is suggested that the applicable MRAM fabrication with the density and capacity higher than 256 Mbit/inch2 even 6 Gbite/inch2 are possible using both I NR-MTJ＋1 transistor structure and current switching mechanism based on based on our fabricated 4×4 MRAM demo devices.
基金Project supported by the National Natural Science Foundation of China (Grant No. 10874021)
文摘The magnetic and electronic properties of the geometrically frustrated triangular antiferromagnet CuCrO2 are investigated by first principles through density functional theory calculations within the generalized gradient approxi- mations （GGA）＋U scheme. The spin exchange interactions up to the third nearest neighbours in the ab plane as well as the coupling between adjacent layers are calculated to examine the magnetism and spin frustration. It is found that CuCrO2 has a natural two-dimensional characteristic of the magnetic interaction. Using Monte Carlo simulation, we obtain the Neel temperature to be 29.9 K, which accords well with the experimental value of 24 K. Based on non- collinear magnetic structure calculations, we verify that the incommensurate spiral-spin structure with （110） spiral plane is believable for the magnetic ground state, which is consistent with the experimental observations. Due to intra-layer geometric spin frustration, parallel helical-spin chains arise along the a, b, or a＋ b directions, each with a screw-rotation angle of about I20°. Our calculations of the density of states show that the spin frustration plays an important role in the change of d-p hybridization, while the spin-orbit coupling has a very limited influence on the electronic structure.
基金Project supported by the National Natural Science Foundation of China （Grant Nos. 11074032, 11074233, and 11274079） and the Natural Science Foundation of Jiangsu Province, China （Grant No. BK20131284）.
文摘We investigate the electron transport in silicene with both staggered electric potential and magnetization; the latter comes from the magnetic proximity effect by depositing silicene on a magnetic insulator. It is shown that the silicene could be a spin and valley half metal under appropriate parameters when the spin–orbit interaction is considered; further, the filtered spin and valley could be controlled by modulating the staggered potential or magnetization. It is also found that in the spin-valve structure of silicene, not only can the antiparallel magnetization configuration significantly reduce the valve-structure conductance, but the reversing staggered electric potential can cause a high-performance magnetoresistance due to the spin and valley blocking effects. Our findings show that the silicene might be an ideal basis for the spin and valley filter analyzer devices.
文摘The realization of a perfect spin or valley filtering effect in two-dimensional graphene-like materials is one of the fundamental objectives in spintronics and valleytronics. For this purpose, we study spin- and valley-dependent transport in a silicene system with spatially alternative strains. It is found that due to the valley-opposite gauge field induced by the strain, the strained silicene with a superlattice structure exhibits an angle-resolved valley and spin filtering effect when the spin–orbit interaction is considered. When the interaction that breaks the time reversal symmetry is introduced, such as the spin or valley dependent staggered magnetization, the system is shown to be a perfect spin and valley half metal in which only one spin and valley species is allowed to transport. Our findings are helpful to design both spintronic and valleytronic devices based on silicene.
基金Project supported by the National Key Basic Research Special Foundation of China (Grant No 2006CB921300)the National Natural Science Foundation of China (Grant No 10604063)
文摘According to the general principle of non-equilibrium thermodynamics, we propose a set of macroscopic transport equations for the spin transport and the charge transport, In particular, the spin torque is introduced as a generalized ＇current density＇ to describe the phenomena associated with the spin non-conservation in a unified framework. The Einstein relations and the Onsager relations between different transport phenomena are established. Specifically, the spin transport properties of the isotropic non-magnetic and the isotropic magnetic two-dimensional electron gases are fully described by using this theory, in which only the macroscopic-spin-related transport phenomena allowed by the symmetry of the system are taken into account.
基金supported by the National Young 1000 Talents Plan of Chinathe Pu Jiang Talent Plan in Shanghai City, China
文摘Topological insulators＇ properties and their potential device applications are reviewed. We also explain why topologi- cal insulator （TI） nanostructnres are an important avenue for research and discuss some methods by which TI nanostructures are produced and characterized. The rapid development of high-quality TI nanostructures provides an ideal platform to ex- ploit salient physical phenomena that have been theoretically predicted but not yet experimentally realized.
