Unconventional antiferromagnetism dubbed as altermagnetism was first discovered in rutile structured magnets,which is featured by spin splitting even without the spin–orbital coupling effect.This interesting phenomen...Unconventional antiferromagnetism dubbed as altermagnetism was first discovered in rutile structured magnets,which is featured by spin splitting even without the spin–orbital coupling effect.This interesting phenomenon has been discovered in more altermagnetic materials.In this work,we explore two-dimensional altermagnetic materials by studying two series of two-dimensional magnets,including MF4 with M covering all 3d and 4d transition metal elements,as well as TS2 with T=V,Cr,Mn,Fe.Through the magnetic symmetry operation of RuF4 and MnS2,it is verified that breaking the time inversion is a necessary condition for spin splitting.Based on symmetry analysis and first-principles calculations,we find that the electronic bands and magnon dispersion experience alternating spin splitting along the same path.This work paves the way for exploring altermagnetism in two-dimensional materials.展开更多
We investigated the spin splitting of vortex beam on the surface of biaxial natural hyperbolic materials(NHMs)rotated by an angle with respect to the incident plane. An obvious asymmetry of spatial shifts produced by ...We investigated the spin splitting of vortex beam on the surface of biaxial natural hyperbolic materials(NHMs)rotated by an angle with respect to the incident plane. An obvious asymmetry of spatial shifts produced by the left-handed circularly(LCP) component and right-handed circularly polarized(RCP) component is exhibited. We derived the analytical expression for in-and out-of-plane spatial shifts for each spin component of the vortex beam. The orientation angle of the optical axis plays a key role in the spin splitting between the two spin components, which can be reflected in the simple expressions for spatial shifts without the rotation angle. Based on an α-MoO_(3) biaxial NHM, the spatial shifts of the two spin components with the topological charge were investigated. As the topological charge increases, the spatial shifts also increase;in addition, a tiny spatial shift close to zero can be obtained if we control the incident frequency or the polarization of the reflected beams. It can also be concluded that the maximum of the spin splitting results from the LCP component at p-incidence and the RCP component at s-incidence in the RB-Ⅱ hyperbolic frequency band. The effect of the incident angle and the thickness of the α-MoO_(3) film on spin splitting is also considered. These results can be used for manipulating infrared radiation and optical detection.展开更多
Rashba spin splitting(RSS)and quantum spin Hall effect(QSHE)have attracted enormous interest due to their great significance in the application of spintronics.In this work,we theoretically proposed a new two-dimension...Rashba spin splitting(RSS)and quantum spin Hall effect(QSHE)have attracted enormous interest due to their great significance in the application of spintronics.In this work,we theoretically proposed a new two-dimensional(2D)material H–Pb–F with coexistence of giant RSS and quantum spin Hall effec by using the ab initio calculations.Our results show that H–Pb–F possesses giant RSS(1.21 eV·A)and the RSS can be tuned up to 4.16 e V·A by in-plane biaxial strain,which is a huge value among 2D materials.Furthermore,we also noticed that H–Pb–F is a 2D topological insulator(TI)duo to the strong spin–orbit coupling(SOC)interaction,and the large topological gap is up to 1.35 e V,which is large enough for for the observation of topological edge states at room temperature.The coexistence of giant RSS and quantum spin Hall effect greatly broadens the potential application of H–Pb–F in the field of spintronic devices.展开更多
Recently, two-dimensional van der Waals(vd W) magnetic heterostructures have attracted intensive attention since they can show remarkable properties due to the magnetic proximity effect. In this work, the spin-polariz...Recently, two-dimensional van der Waals(vd W) magnetic heterostructures have attracted intensive attention since they can show remarkable properties due to the magnetic proximity effect. In this work, the spin-polarized electronic structures of antimonene/Fe_(3)GeTe_(2)vdW heterostructures were investigated through the first-principles calculations. Owing to the magnetic proximity effect, the spin splitting appears at the conduction-band minimum(CBM) and the valence-band maximum(VBM) of the antimonene. A low-energy effective Hamiltonian was proposed to depict the spin splitting. It was found that the spin splitting can be modulated by means of applying an external electric field, changing interlayer distance or changing stacking configuration. The spin splitting energy at the CBM monotonously increases as the external electric field changes from-5 V/nm to 5 V/nm, while the spin splitting energy at the VBM almost remains the same. Meanwhile,as the interlayer distance increases, the spin splitting energies at the CBM and VBM both decrease. The different stacking configurations can also induce different spin splitting energies at the CBM and VBM. Our work demonstrates that the spin splitting of antimonene in this heterostructure is not singly dependent on the nearest Sb–Fe distance, which indicates that magnetic proximity effect in heterostructures may be modulated by multiple factors, such as hybridization of electronic states and the local electronic environment. The results enrich the fundamental understanding of the magnetic proximity effect in two-dimensional vdW heterostructures.展开更多
We theoretically investigate the spin-orbit interaction in GaAs/AlxGal_xAs coupled quantum wells. We consider the contribution of the interface-related Rashba term as well as the linear and cubic Dresselhaus terms to ...We theoretically investigate the spin-orbit interaction in GaAs/AlxGal_xAs coupled quantum wells. We consider the contribution of the interface-related Rashba term as well as the linear and cubic Dresselhaus terms to the spin splitting. For the coupled quantum wells which bear an inherent structure inversion asymmetry, the same probability density distribution of electrons in the two step quantum wells results in a large spin splitting from the interface term. If the widths of the two step quantum wells are different, the electron probability density in the wider step quantum well is considerably higher than that in the narrower one, resulting in the decrease of the spin splitting from the interface term. The results also show that the spin splitting of the coupled quantum well is not significantly larger than that of a step quantum well.展开更多
Optical spin splitting has attracted significant attention owing to its potential applications in quantum information and precision metrology. However, it is typically small and cannot be controlled efficiently. Here,...Optical spin splitting has attracted significant attention owing to its potential applications in quantum information and precision metrology. However, it is typically small and cannot be controlled efficiently. Here, we enhance the spin splitting by transmitting higher-order Laguerre–Gaussian(LG) beams through graphene metamaterial slabs. The interaction between LG beams and metamaterial results in an orbital-angularmomentum-(OAM) dependent spin splitting. The upper bound of the OAM-dependent spin splitting is found,which varies with the incident OAM and beam waist. Moreover, the spin splitting can be flexibly tuned by modulating the Fermi energy of the graphene sheets. This tunable spin splitting has potential applications in the development of spin-based applications and the manipulation of mid-infrared waves.展开更多
Rashba spin splitting （RSS） in quantum-spin Hall （QSH） insulators is of special importance for fabricating spintronic devices. By changing the stacking order, a unique bilayered fluorinated arsenene （AsF） system...Rashba spin splitting （RSS） in quantum-spin Hall （QSH） insulators is of special importance for fabricating spintronic devices. By changing the stacking order, a unique bilayered fluorinated arsenene （AsF） system is demonstrated to simultaneously possess RSS and non-trivial topological electronic states. We show by first-principle calculations that tunable RSS can be realized in bilayered AsF. Intrinsic RSS of 25 meV is obtained in the AA-stacked AsF bilayer by considering the spin-orbit coupling effect. The RSS can be tuned in the range of 0 to 50 meV by applying biaxial strains and can be significantly enhanced up to 186 meV in the presence of an external electric field. The AB-stacked AsF bilayer is shown to be a two-dimensional topological insulator with a sizable bulk bandgap of 140 meV （up to 240 meV）, which originates from the spin-orbit coupling within the p~,y-pz band inversion. Surprisingly, RSS up to 295 meV can be induced in the AB-stacked AsF bilayer by applying an external electric field, while the robust topology property without RSS can be retained under the applied strains. The AsF bilayers with tunable RSS and a nontrivial bandgap with AA- and AB-stacking orders can pave the way for designing spin field-effect transistors and new QSH devices.展开更多
The Rashba coefficient and Rashba spin splitting for the first subband of the Alo.5Gao.5N/GaN/ Alo.5Gao.5N quantum well （QW） with various sheet carrier densities （Ns） are calculated by solving Schr6dinger and Pois...The Rashba coefficient and Rashba spin splitting for the first subband of the Alo.5Gao.5N/GaN/ Alo.5Gao.5N quantum well （QW） with various sheet carrier densities （Ns） are calculated by solving Schr6dinger and Poisson equations self-consistently. The Rashba spin splitting for the first subband at the Fermi level is considerable and increases evidently with Ns, since the Rashba coefficient, especially the Fermi wave vector increase rapidly. With increasing Ns, the peak of the wave function for the first subband moves towards the left heterointerface, and the average electric field in the well increases, so the two dominant contributions coming from the well and the heterointerface increase. Therefore, the strong polarization electric field and high density of 2DEG in III-nitrides heterostructures are of great importance to a and make the Rashba spin splitting in A1GaN/GaN QWs comparable to that of narrow-gap III-V materials. The results indicate that the sheet carrier density is an important parameter affecting the Rashba coefficient and Rashba spin splitting in A1GaN/GaN QWs, showing the possible application of this material system in spintronic devices.展开更多
In this paper, we obtain considerable spin-orbit （SO） parameters in AlxGa1-xN/GaN quantum wells （QWs） with sheet carrier concentration N8 = 120 × 10^11/cm^2. With increasing AI content （x） of the barrier, t...In this paper, we obtain considerable spin-orbit （SO） parameters in AlxGa1-xN/GaN quantum wells （QWs） with sheet carrier concentration N8 = 120 × 10^11/cm^2. With increasing AI content （x） of the barrier, the SO parameters increase as a whole, and the two major contributions are found to be the decrease of the expansion region of the envelope functions and the increase of the polarized electric field in the well. Compared with the Rashba parameters for the first two subbands, the intersubband SO parameter is a bit smaller and varies more slowly with x. The results indicate the SO parameters, especially the Rashba parameters can be engineered by the AI composition of the barrier, which may be helpful to the spin manipulation of III-nitride low-dimensional heterostructures.展开更多
A quantum-spin-Hall （QSH） state was achieved experimentally, albeit at a low critical temperature because of the narrow band gap of the bulk material. Two- dimensional topological insulators are critically important...A quantum-spin-Hall （QSH） state was achieved experimentally, albeit at a low critical temperature because of the narrow band gap of the bulk material. Two- dimensional topological insulators are critically important for realizing novel topological applications. Using density functional theory （DFT）, we demonstrated that hydrogenated GaBi bilayers （HGaBi） form a stable topological insulator with a large nontrivial band gap of 0.320 eV, based on the state-of-the-art hybrid functional method, which is implementable for achieving QSH states at room temperature. The nontrivial topological property of the HGaBi lattice can also be confirmed from the appearance of gapless edge states in the nanoribbon structure. Our results provide a versatile platform for hosting nontrivial topological states usable for important nanoelectronic device applications.展开更多
基金the National Natural Science Foundation of China(Grant No.12004439)Hunan Province Postgraduate Research and Innovation Project(Grant No.CX20230229)the computational resources from the High Performance Computing Center of Central South University.
文摘Unconventional antiferromagnetism dubbed as altermagnetism was first discovered in rutile structured magnets,which is featured by spin splitting even without the spin–orbital coupling effect.This interesting phenomenon has been discovered in more altermagnetic materials.In this work,we explore two-dimensional altermagnetic materials by studying two series of two-dimensional magnets,including MF4 with M covering all 3d and 4d transition metal elements,as well as TS2 with T=V,Cr,Mn,Fe.Through the magnetic symmetry operation of RuF4 and MnS2,it is verified that breaking the time inversion is a necessary condition for spin splitting.Based on symmetry analysis and first-principles calculations,we find that the electronic bands and magnon dispersion experience alternating spin splitting along the same path.This work paves the way for exploring altermagnetism in two-dimensional materials.
基金Project supported by the Natural Science Foundation of Heilongjiang Province of China (Grant No. LH2022F041)。
文摘We investigated the spin splitting of vortex beam on the surface of biaxial natural hyperbolic materials(NHMs)rotated by an angle with respect to the incident plane. An obvious asymmetry of spatial shifts produced by the left-handed circularly(LCP) component and right-handed circularly polarized(RCP) component is exhibited. We derived the analytical expression for in-and out-of-plane spatial shifts for each spin component of the vortex beam. The orientation angle of the optical axis plays a key role in the spin splitting between the two spin components, which can be reflected in the simple expressions for spatial shifts without the rotation angle. Based on an α-MoO_(3) biaxial NHM, the spatial shifts of the two spin components with the topological charge were investigated. As the topological charge increases, the spatial shifts also increase;in addition, a tiny spatial shift close to zero can be obtained if we control the incident frequency or the polarization of the reflected beams. It can also be concluded that the maximum of the spin splitting results from the LCP component at p-incidence and the RCP component at s-incidence in the RB-Ⅱ hyperbolic frequency band. The effect of the incident angle and the thickness of the α-MoO_(3) film on spin splitting is also considered. These results can be used for manipulating infrared radiation and optical detection.
基金the National Natural Science Foundation of China(Grant Nos.11874316,11404275,and 11474244)the National Basic Research Program of China(Grant No.2015CB921103)+2 种基金the Natural Science Foundation of Hunan Province,China(Grant Nos.2016JJ3118 and 2020JJ4244)the Scientific Research Foundation of the Education Bureau of Hunan Province,China(Grant Nos.16K084,17K086,and 21A049)the Fund for the Innovative Research Team in University(Grant No.IRT13093).
文摘Rashba spin splitting(RSS)and quantum spin Hall effect(QSHE)have attracted enormous interest due to their great significance in the application of spintronics.In this work,we theoretically proposed a new two-dimensional(2D)material H–Pb–F with coexistence of giant RSS and quantum spin Hall effec by using the ab initio calculations.Our results show that H–Pb–F possesses giant RSS(1.21 eV·A)and the RSS can be tuned up to 4.16 e V·A by in-plane biaxial strain,which is a huge value among 2D materials.Furthermore,we also noticed that H–Pb–F is a 2D topological insulator(TI)duo to the strong spin–orbit coupling(SOC)interaction,and the large topological gap is up to 1.35 e V,which is large enough for for the observation of topological edge states at room temperature.The coexistence of giant RSS and quantum spin Hall effect greatly broadens the potential application of H–Pb–F in the field of spintronic devices.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 11774434, 11974431, and 11832019)supported by National Supercomputer Center in Guangzhou。
文摘Recently, two-dimensional van der Waals(vd W) magnetic heterostructures have attracted intensive attention since they can show remarkable properties due to the magnetic proximity effect. In this work, the spin-polarized electronic structures of antimonene/Fe_(3)GeTe_(2)vdW heterostructures were investigated through the first-principles calculations. Owing to the magnetic proximity effect, the spin splitting appears at the conduction-band minimum(CBM) and the valence-band maximum(VBM) of the antimonene. A low-energy effective Hamiltonian was proposed to depict the spin splitting. It was found that the spin splitting can be modulated by means of applying an external electric field, changing interlayer distance or changing stacking configuration. The spin splitting energy at the CBM monotonously increases as the external electric field changes from-5 V/nm to 5 V/nm, while the spin splitting energy at the VBM almost remains the same. Meanwhile,as the interlayer distance increases, the spin splitting energies at the CBM and VBM both decrease. The different stacking configurations can also induce different spin splitting energies at the CBM and VBM. Our work demonstrates that the spin splitting of antimonene in this heterostructure is not singly dependent on the nearest Sb–Fe distance, which indicates that magnetic proximity effect in heterostructures may be modulated by multiple factors, such as hybridization of electronic states and the local electronic environment. The results enrich the fundamental understanding of the magnetic proximity effect in two-dimensional vdW heterostructures.
基金Project supported by the National Natural Science Foundation of China (Grant No. 61204107)the Scientific Research Fund of Zhejiang Provincial Education Department, China (Grant No. Y201120799)
文摘We theoretically investigate the spin-orbit interaction in GaAs/AlxGal_xAs coupled quantum wells. We consider the contribution of the interface-related Rashba term as well as the linear and cubic Dresselhaus terms to the spin splitting. For the coupled quantum wells which bear an inherent structure inversion asymmetry, the same probability density distribution of electrons in the two step quantum wells results in a large spin splitting from the interface term. If the widths of the two step quantum wells are different, the electron probability density in the wider step quantum well is considerably higher than that in the narrower one, resulting in the decrease of the spin splitting from the interface term. The results also show that the spin splitting of the coupled quantum well is not significantly larger than that of a step quantum well.
基金National Natural Science Foundation of China(NSFC)(61505069,61675092,61705086)Guangzhou Science and Technology Program key projects(2017A010102006,2017A030313375)
文摘Optical spin splitting has attracted significant attention owing to its potential applications in quantum information and precision metrology. However, it is typically small and cannot be controlled efficiently. Here, we enhance the spin splitting by transmitting higher-order Laguerre–Gaussian(LG) beams through graphene metamaterial slabs. The interaction between LG beams and metamaterial results in an orbital-angularmomentum-(OAM) dependent spin splitting. The upper bound of the OAM-dependent spin splitting is found,which varies with the incident OAM and beam waist. Moreover, the spin splitting can be flexibly tuned by modulating the Fermi energy of the graphene sheets. This tunable spin splitting has potential applications in the development of spin-based applications and the manipulation of mid-infrared waves.
文摘Rashba spin splitting （RSS） in quantum-spin Hall （QSH） insulators is of special importance for fabricating spintronic devices. By changing the stacking order, a unique bilayered fluorinated arsenene （AsF） system is demonstrated to simultaneously possess RSS and non-trivial topological electronic states. We show by first-principle calculations that tunable RSS can be realized in bilayered AsF. Intrinsic RSS of 25 meV is obtained in the AA-stacked AsF bilayer by considering the spin-orbit coupling effect. The RSS can be tuned in the range of 0 to 50 meV by applying biaxial strains and can be significantly enhanced up to 186 meV in the presence of an external electric field. The AB-stacked AsF bilayer is shown to be a two-dimensional topological insulator with a sizable bulk bandgap of 140 meV （up to 240 meV）, which originates from the spin-orbit coupling within the p~,y-pz band inversion. Surprisingly, RSS up to 295 meV can be induced in the AB-stacked AsF bilayer by applying an external electric field, while the robust topology property without RSS can be retained under the applied strains. The AsF bilayers with tunable RSS and a nontrivial bandgap with AA- and AB-stacking orders can pave the way for designing spin field-effect transistors and new QSH devices.
基金Project supported by the National Natural Science Foundation of China(Nos.61306012,11004168)the Program for Science & Technology Innovation Talents in Universities of Henan Province(No.2012HASTIT033)
文摘The Rashba coefficient and Rashba spin splitting for the first subband of the Alo.5Gao.5N/GaN/ Alo.5Gao.5N quantum well （QW） with various sheet carrier densities （Ns） are calculated by solving Schr6dinger and Poisson equations self-consistently. The Rashba spin splitting for the first subband at the Fermi level is considerable and increases evidently with Ns, since the Rashba coefficient, especially the Fermi wave vector increase rapidly. With increasing Ns, the peak of the wave function for the first subband moves towards the left heterointerface, and the average electric field in the well increases, so the two dominant contributions coming from the well and the heterointerface increase. Therefore, the strong polarization electric field and high density of 2DEG in III-nitrides heterostructures are of great importance to a and make the Rashba spin splitting in A1GaN/GaN QWs comparable to that of narrow-gap III-V materials. The results indicate that the sheet carrier density is an important parameter affecting the Rashba coefficient and Rashba spin splitting in A1GaN/GaN QWs, showing the possible application of this material system in spintronic devices.
文摘In this paper, we obtain considerable spin-orbit （SO） parameters in AlxGa1-xN/GaN quantum wells （QWs） with sheet carrier concentration N8 = 120 × 10^11/cm^2. With increasing AI content （x） of the barrier, the SO parameters increase as a whole, and the two major contributions are found to be the decrease of the expansion region of the envelope functions and the increase of the polarized electric field in the well. Compared with the Rashba parameters for the first two subbands, the intersubband SO parameter is a bit smaller and varies more slowly with x. The results indicate the SO parameters, especially the Rashba parameters can be engineered by the AI composition of the barrier, which may be helpful to the spin manipulation of III-nitride low-dimensional heterostructures.
文摘A quantum-spin-Hall （QSH） state was achieved experimentally, albeit at a low critical temperature because of the narrow band gap of the bulk material. Two- dimensional topological insulators are critically important for realizing novel topological applications. Using density functional theory （DFT）, we demonstrated that hydrogenated GaBi bilayers （HGaBi） form a stable topological insulator with a large nontrivial band gap of 0.320 eV, based on the state-of-the-art hybrid functional method, which is implementable for achieving QSH states at room temperature. The nontrivial topological property of the HGaBi lattice can also be confirmed from the appearance of gapless edge states in the nanoribbon structure. Our results provide a versatile platform for hosting nontrivial topological states usable for important nanoelectronic device applications.
