176 results on '"SPIN polarization"'
Search Results
2. Anomalous spin Josephson effect in spin superconductors.
- Author
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Zeng, Wen and Shen, Rui
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SUPERCONDUCTORS , *JOSEPHSON junctions , *JOSEPHSON effect , *SPIN polarization , *TIME reversal , *BREWSTER'S angle , *BOSE-Einstein condensation - Abstract
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 possible π -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. [ABSTRACT FROM AUTHOR]
- Published
- 2024
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3. Robust photogalvanic effect, full spin polarization and pure spin current in the BiC photodetector by vacancy and substitution-doping.
- Author
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Fu, Xi, Lin, Jian, He, Chaozheng, Liao, Wenhu, Guo, Jiyuan, Li, Xiaowu, and Gao, Haixia
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PHOTOCONDUCTIVITY , *PHOTODETECTORS , *SPIN polarization , *GREEN'S functions , *SPIN-orbit interactions , *ELECTROLYTIC corrosion , *DENSITY functional theory - Abstract
The photogalvanic effects (PGEs) in low-dimensional devices have attracted great interests recently. Herein, based on non-equilibrium Green's function combined with density functional theory, we investigated spin-dependent PGE phenomena in the BiC photodetector with the linearly polarized light and zero bias. Due to the presence of strong spin–orbit interaction (SOI) and C 3 v symmetry for the BiC monolayer, the armchair and zigzag BiC photodetectors can produce robust spin-dependent PGEs which possess the cos(2 θ) and sin(2 θ) relations on the photon energies, respectively. Especially, the pristine armchair and armchair Bi-vacancy BiC photodetectors can produce fully spin polarization, and pure spin current was found in the pristine armchair and zigzag BiC photodetector, respectively. Furthermore, after introducing the Bi-vacancy, C-vacancy, Bi-doping and C-doping respectively, the BiC photodetector can produce higher spin-dependent PGEs for their C s symmetry. Additionally, the behaviors of spin-dependent photoresponse are highly anisotropic which can be tuned by the photon energy. This work suggested great potential applications of the BiC monolayer on PGE-driven photodetectors in low energy-consumption optoelectronics and spintronic devices. [ABSTRACT FROM AUTHOR]
- Published
- 2024
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4. Valleytronic topological filters in silicene-like inner-edge systems.
- Author
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Xie, Hang, Lü, Xiao-Long, and Yang, Jia-En
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DEGREES of freedom , *ELECTROSTATIC discharges , *SPIN polarization , *TOPOLOGICAL insulators - Abstract
Inner edge state with spin and valley degrees of freedom is a promising candidate for designing a dissipationless device due to the topological protection. The central challenge for the application of the inner edge state is to generate and modulate the polarized currents. In this work, we discover a new mechanism to generate fully valley- and spin–valley-polarized current caused by the Bloch wavevector mismatch (BWM). Based on this mechanism, we design some serial-typed inner-edge filters. By using once of the BWM, the coincident states could be divided into transmitted and reflected modes, which can serve as a valley or spin–valley filter. In particular, while with twice of the BWM, the incident current is absolutely reflected to support an off state with a specified valley and spin, which is different from the gap effect. These findings give rise to a new platform for designing valleytronics and spin-valleytronics. [ABSTRACT FROM AUTHOR]
- Published
- 2024
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5. Continuous phase transition induced by non-Hermiticity in the quantum contact process model.
- Author
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He, Wen-Bin, Jin, Jiasen, Iemini, Fernando, and Lin, Hai-Qing
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PHASE transitions , *CRITICAL exponents , *SPIN polarization - Abstract
Non-Hermitian (NH) quantum system recently have attracted a lots of attentions theoretically and experimentally. However, the results based on the single-particle picture may not apply to understand the property of NH many-body system. How the property of quantum many-body system especially the phase transition will be affected by the non-Hermiticity remains unclear. Here we study NH quantum contact process (QCP) model, whose effective Hamiltonian is derived from Lindbladian master equation. We show that there is a continuous phase transition induced by the non-Hermiticity in QCP. We also determine the critical exponents β of order parameter, γ of susceptibility and study the correlation and entanglement near phase transition point. We observe that the order parameter and susceptibility display infinitely singularity even for finite size system, since non-Hermiticity endow many-body system with different singular behavior from classical phase transition. Moreover our results show that the phase transition have no counterpart in Hermitian case and belongs to completely different universality class. [ABSTRACT FROM AUTHOR]
- Published
- 2023
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6. Spin filtration in generalized Sierpinski triangles in presence of Rashba spin–orbit interaction.
- Author
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Majhi, Joydeep and Maiti, Santanu K
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SPIN-orbit interactions , *TRIANGLES , *SPIN polarization , *GEOMETRICAL constructions , *ELECTRONIC equipment , *GREEN'S functions - Abstract
In this work, we theoretically investigate the phenomenon of spin polarization in generalized Sierpinski gasket (SPG) triangles ( Δ N N N , Δ F N N , Δ F F N , Δ F F F) in the presence of Rashba spin–orbit interaction (RSOI) within a tight-binding framework. The geometrical construction is addressed for all four types of generalized SPG triangles using an iterative function system that begins with a fixed triangle of any arbitrary side length. The geometry of various types of fractal networks has a major impact on the degeneracy of the energy spectrum. It is shown that only the two-terminal setup in the presence of RSOI is incapable of breaking the spin degeneracy, which necessitates the use of a three-terminal setup to break the time-reversal symmetry. The effect of flip map induced anisotropic hopping integrals on three-terminal spin-resolved transmission probabilities is studied. In several cases, we find almost 100 % spin polarization in our considered lattices. We also analyze how spin polarization varies with RSOI strength and fractal generations. Our results indicate that fractal lattices might be suitable functional elements for designing future spin-based electronic devices. [ABSTRACT FROM AUTHOR]
- Published
- 2023
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7. Equal-spin Andreev reflection in antiferromagnet/normal/superconductor junctions with Rashba spin–orbit coupling.
- Author
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Niu, Zhi Ping and Zhang, Yong Mei
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ANDREEV reflection , *SPIN-orbit interactions , *ANTIFERROMAGNETIC materials , *SUPERCONDUCTORS , *SPIN polarization , *ELECTRIC potential - Abstract
We have theoretically investigated the Andreev reflection (AR)-induced conductance spectra through antiferromagnet/normal layer/superconductor junctions with hexagonal lattices. When the PT symmetry is broken by the staggered sublattice potential, antiferromagnet may exhibit spin polarization. A gap-edge conductance peak is usually shown, reflecting the characteristic of conventional AR. Equal-spin AR can be generated by the spin-flip scattering caused by Rashba spin–orbit coupling in the normal layer. Surprisingly, when the equal-spin AR process dominates, the conductance peak divides into two peaks near the singlet-gap energy, indicating the existence of spin-triplet pairings in the antiferromagnet. Furthermore, as the amplitudes of the conventional and equal-spin ARs can be modulated by the staggered sublattice potential and electrostatic potential, a conversion from the conductance peak to the conductance peak splitting can be realized, which can help us to distinguish between the spin-singlet and spin-triplet pairings. These findings make the antiferromagnet/superconductor junctions as promising platforms for future superconducting spintronics applications. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
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8. Spin-induced valley polarization in heterobilayer Janus transition-metal dichalcogenides.
- Author
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Liu, Huating, Huang, Zongyu, Luo, Chaobo, Guo, Gencai, Peng, Xiangyang, Qi, Xiang, and Zhong, Jianxin
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SPINTRONICS , *MAGNETIC anisotropy , *MAGNETIC transitions , *SPIN-orbit interactions , *HEUSLER alloys , *INTERNAL friction - Abstract
Inspired by potential application prospects of spintronics and valleytronics, a novel heterobilayer Janus structure is designed by replacing the chalcogenide atomic layers in the original bilayer MoS2. Based on first-principles calculations, it is found that the SMoS/SeMoS structure exhibits a direct band-gap semiconductor and a typical type-II band alignment with longer carrier lifetime. The transition metal (TM) atom represented by V/Cr/Mn can be stably adsorbed on the heterobilayer Janus SMoS/SeMoS sheet and effectively introduce magnetic moments (m). The calculation results demonstrate that the most stable adsorption site of the TM atom is CX(A), and the TM (V/Cr/Mn) adatom modified SMoS/SeMoS system is converted into metal (V-) or half-metal (Cr/Mn-), respectively. Under the coupling of different indirect exchange interactions, the structure exhibits stable intrinsic anti-ferromagnetic interactions for V-SMoS/SeMoS and ferromagnetic ground state for Cr/Mn-SMoS/SeMoS, respectively, and the magnetic transition temperature (T c) reaches a high temperature or even room temperature. Moreover, the robust out-of-plane magnetocrystalline anisotropy energy ensures stable long-range magnetic order. Specifically, the combination of spin injection and strong spin–orbit coupling interaction effectively breaks the time-reversal symmetry, which leads to valley polarization of the system. Based on this, the biaxial strain can effectively regulate the electronic structure, magnetic properties and valley polarization of TM-SMoS/SeMoS nanosheets with double breaking of spatial-inversion and time-reversal symmetry. [ABSTRACT FROM AUTHOR]
- Published
- 2023
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9. First-principles studies of charged defect states in intrinsic ferromagnetic semiconductors: the case of monolayer CrI3.
- Author
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Zhu, Guo-Jun, Xu, Yong-Gang, Fang, Yi-Bin, Yang, Ji-Hui, and Gong, Xin-Gao
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SEMICONDUCTORS , *MONOMOLECULAR films , *SPIN polarization , *MAGNETIC semiconductors , *SEMICONDUCTOR defects , *MAGNETIC properties - Abstract
Defects play significant roles in spin-current-related physical processes in intrinsic ferromagnetic semiconductors (FMSs), which are great promise for spintronics applications. However, current defect calculation methods cannot be used to investigate charged defects in FMSs due to the spin polarization of both the charged defect states and ionized carriers, which is not well treated in current defect calculation methods. In order to solve this problem, we propose a spin-distinguishable charge correction (SDCC) method that uses spin-polarized band edge charge density instead of spin-unpolarized uniform background charge density as the compensating charge for charged defects. We apply our method to study the defect properties of CrI3 monolayer and find it can be doped n-type under the Cr-rich growth condition but difficult to be doped p-type. The SDCC method proposed here is generally suitable for all FMSs, which will be useful for the studies of defect properties of magnetic semiconductors. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
10. Probe beam influence on spin polarization in spin-exchange relaxation-free co-magnetometers.
- Author
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Wei, Yao, Xing, Li, Zhai, Yueyang, Fan, Wenfeng, Fang, Chi, Liu, Feng, and Quan, Wei
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SPIN polarization , *STEADY-state responses , *BLOCH equations , *ELECTRON spin , *CIRCULAR polarization , *OPTICAL pumping - Abstract
Spin-exchange relaxation-free (SERF) co-magnetometers have promising applications in both inertial navigation and fundamental physics experiments. However, the fluctuation in the spin polarization caused by the probe beam has a non-negligible influence on the co-magnetometer signal. In this paper, a theoretical model containing three parameters of the probe beam is established by extending the coupled Bloch equation. Based on this model, the influence of probe power density on the transient and steady-state response of the SERF co-magnetometer is analyzed. According to the transient response model, a new measurement method for transverse optical pumping of the probe beam is proposed. Then, for the steady-state response model, a steady-state error suppression method is suggested by adjusting the degree of circular polarization of the probe beam. Eventually, the suppression method is used to refine the SERF co-magnetometer, achieving a suppression rate of 70.31% in transverse electron spin polarization fluctuations, thus improving the co-magnetometer to a stability of 0.0079∘ h−1. To our knowledge, this is better than what has been reported so far. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
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11. Anisotropy of Electronic Spin Texture in the High-Temperature Cuprate Superconductor Bi2Sr2CaCu2O8+ δ .
- Author
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Liu, Wenjing, Zha, Heming, Gu, Gen-Da, Shen, Xiaoping, Ye, Mao, and Qiao, Shan
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CUPRATES , *HIGH temperature superconductors , *CONDENSED matter physics , *PHOTOELECTRON spectroscopy , *PHASE transitions , *ANISOTROPY , *SPIN polarization - Abstract
Seeking new order parameters and the related broken symmetry and studying their relationship with phase transition have been important topics in condensed matter physics. Here, by using spin- and angle-resolved photoemission spectroscopy, we confirm the helical spin texture caused by spin-layer locking in the nodal region in the cuprate superconductor Bi2Sr2CaCu2O8+ δ and discover the anisotropy of spin polarizations at nodes along Γ – X and Γ – Y directions. The breaking of C 4 rotational symmetry in electronic spin texture may give deeper insights into understanding the ground state of cuprate superconductors. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
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12. Spin and polarization: a new direction in relativistic heavy ion physics.
- Author
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Becattini, Francesco
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SPIN polarization , *HEAVY ions , *QUANTUM field theory , *COLLISIONS (Nuclear physics) , *PHYSICS - Abstract
Since the first evidence of a global polarization of Λ hyperons in relativistic nuclear collisions in 2017, spin has opened a new window in the field, both at experimental and theoretical level, and an exciting perspective. The current state of the field is reviewed with regard to the theoretical understanding of the data, reporting on the most recent achievements and envisioning possible developments. The intriguing connections of spin physics in relativistic matter with fundamental questions in quantum field theory and applications in the non-relativistic domain are discussed. [ABSTRACT FROM AUTHOR]
- Published
- 2022
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13. Enhancement of spin-orbit torque efficiency by tailoring interfacial spin-orbit coupling in Pt-based magnetic multilayers.
- Author
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Wang, Wenqiang, Zhu, Gengkuan, Zhou, Kaiyuan, Zhan, Xiang, Tao, Zui, Fu, Qingwei, Liang, Like, Li, Zishuang, Chen, Lina, Yan, Chunjie, Li, Haotian, Zhou, Tiejun, and Liu, Ronghua
- Subjects
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SPIN-orbit interactions , *ANOMALOUS Hall effect , *SPIN Hall effect , *PERPENDICULAR magnetic anisotropy , *SPIN polarization , *TORQUE - Abstract
We study inserting Co layer thickness-dependent spin transport and spinâ€"orbit torques (SOTs) in the Pt/Co/Py trilayers by spin-torque ferromagnetic resonance. The interfacial perpendicular magnetic anisotropy (IPMA) energy density (K s = 2.7 erg/cm2, 1 erg = 10â'7 J), which is dominated by interfacial spinâ€"orbit coupling (ISOC) in the Pt/Co interface, total effective spin-mixing conductance (G eff , tot â†' â†" = 0. 42 Ă— 10 15 Ω â' 1 â‹... m â' 2 ) and two-magnon scattering (β TMS = 0.46 nm2) are first characterized, and the damping-like torque (Îľ DL = 0.103) and field-like torque (Îľ FL = â€"0.017) efficiencies are also calculated quantitatively by varying the thickness of the inserting Co layer. The significant enhancement of Îľ DL and Îľ FL in Pt/Co/Py than Pt/Py bilayer system originates from the interfacial Rashbaâ€"Edelstein effect due to the strong ISOC between Co-3d and Pt-5d orbitals at the Pt/Co interface. Additionally, we find a considerable out-of-plane spin polarization SOT, which is ascribed to the spin anomalous Hall effect and possible spin precession effect due to IPMA-induced perpendicular magnetization at the Pt/Co interface. Our results demonstrate that the ISOC of the Pt/Co interface plays a vital role in spin transport and SOTs-generation. Our finds offer an alternative approach to improve the conventional SOTs efficiencies and generate unconventional SOTs with out-of-plane spin polarization to develop low power Pt-based spintronic via tailoring the Pt/FM interface. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
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14. High Chern number phase in topological insulator multilayer structures: A Dirac cone model study.
- Author
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Wang, Yi-Xiang and Li, Fu-Xiang
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TOPOLOGICAL insulators , *SPIN polarization , *CONES , *PHASE diagrams , *DIRAC function - Abstract
We employ the Dirac cone model to explore the high Chern number (C) phases that are realized in the magnetic-doped topological insulator (TI) multilayer structures by Zhao et al. [ Nature 588 419 (2020)]. The Chern number is calculated by capturing the evolution of the phase boundaries with the parameters, then the Chern number phase diagrams of the TI multilayer structures are obtained. The high- C behavior is attributed to the band inversion of the renormalized Dirac cones, along with which the spin polarization at the Î" point will get increased. Moreover, another two TI multilayer structures as well as the TI superlattice structures are studied. [ABSTRACT FROM AUTHOR]
- Published
- 2022
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15. Effect of off-stoichiometric composition on half-metallic character of Co2Fe(Ga,Ge) investigated using saturation magnetization and giant magnetoresistance effect.
- Author
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Chikaso, Yuki, Inoue, Masaki, Tanimoto, Tessei, Kikuchi, Keita, Yamanouchi, Michihiko, Uemura, Tetsuya, Inubushi, Kazuumi, Nakada, Katsuyuki, Shinya, Hikari, and Shirai, Masafumi
- Subjects
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GIANT magnetoresistance , *MAGNETIZATION , *MAGNETORESISTANCE , *SPIN polarization , *MAGNETIC moments , *THIN films , *GALLIUM alloys - Abstract
We investigated the Ge-composition (Îł) dependence of the saturation magnetization of Co2Fe(Ga, Ge) (CFGG) thin films and the magnetoresistance (MR) ratio of CFGG-based current-perpendicular-to-plane giant magnetoresistance (CPP-GMR) devices together with first-principles calculations of the electronic states of CFGG. Theoretical calculations showed that spin polarization is highest at the stoichiometric composition Îł = 0.56 in Co2Fe1.03Ga0.41Ge Îł and that it decreases in off-stoichiometric CFGG, mainly due to the formation of CoFe antisites for Ge-deficient compositions and FeCo antisites for Ge-rich compositions, where CoFe (FeCo) indicates that Co (Fe) atoms replace the Fe (Co) sites. The saturation magnetic moment (ÎĽ s) per formula unit decreased monotonically as Îł increased from 0.24 to 1.54 in Co2Fe1.03Ga0.41Ge Îł. The ÎĽ s was closest to the Slaterâ€"Pauling value predicted for half-metallic CFGG at the stoichiometric composition Îł = 0.56, indicating that stoichiometric CFGG has a half-metallic nature. This is consistent with the result for the theoretical spin polarization. In contrast, the MR ratio of CFGG-based CPP-GMR devices increased monotonically as Îł increased from 0.24 to 1.10 and reached an MR ratio of 87.9% at the Ge-rich composition Îł = 1.10. Then, the MR ratio decreased rapidly as Îł increased from 1.10 to 1.48. Possible origins for the slight difference between the Ge composition at which the highest MR ratio was obtained (Îł = 1.10) and that at which the highest spin polarization was obtained (Îł = 0.56) are improved atomic arrangements in a Ge-rich CFGG film and the reduction of effective Ge composition due to Ge diffusion in the GMR stacks. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
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16. 2D spin transport through graphene-MnBi2Te4 heterojunction.
- Author
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Chen, Xi and Lin, Zheng-Zhe
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HETEROJUNCTIONS , *SPIN polarization , *MAGNETIC semiconductors , *TOPOLOGICAL insulators , *BORON nitride , *SEMICONDUCTORS , *ANTIFERROMAGNETIC materials , *OHMIC contacts - Abstract
The development of two-dimensional (2D) magnetic semiconductors promotes the study of nonvolatile control of magnetoelectric nanodevices. MnBi2Te4 is the first realization of antiferromagnetic topological insulator. In semiconductor circuits, metal-semiconductor contacts are usually essential. In future all-carbon circuits, graphene is a promising material for 2D conductive connections. This work studies electronic transport through graphene-MnBi2Te4-graphene junctions. We find that graphene-MnBi2Te4 interfaces are perfect Ohmic contacts, which benefits the use of MnBi2Te4 in carbon circuits. The currents through MnBi2Te4 junctions possess high spin polarization. Compared with usual van der Waals junctions, lateral graphene-MnBi2Te4-graphene junctions present a lower barrier and much higher conductance to electrons. These findings may provide guidance for further study of 2D spin filtering. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
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17. Resonance signatures in DCS and spin polarization for positron scattering with C60 and rare gas endohedrals.
- Author
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Dubey, Km Akanksha and Ciappina, Marcelo F
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SPIN polarization , *SCATTERING (Physics) , *NOBLE gases , *DIFFERENTIAL cross sections , *POSITRONIUM , *ELECTRON spin - Abstract
We present a comparative study of differential cross sections (DCSs) and spin polarizations for positron scattering from C60 and A@C60, elucidating the role of encapsulation of rare gas atoms inside the giant C60 cage. A comparison is provided with the earlier work for elastic positron-C60 scattering. We find a very good agreement even when a model potential is used for the positron-C60 interaction. Also, we evaluate similarities and differences between the positron and electron DCSs and spin polarizations, both from bare and endohedral targets. To mark resonance features on the scattering dynamics, DCSs and spin polarizations are calculated at resonant energies, which showcase different characteristics compared to the cases where the positron energy is non-resonant. In order to account for a complete picture of the scattering process, an absorption potential is included in the total scattering field. For the sake of illustrating the impact of individual interactions and their interplay as a whole, DCSs and spin polarizations are reported including several scattering interactions alternatively. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
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18. Study on a new manner of the magnetization switching actuated by a unidirectional pulse current.
- Author
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Li, K, Feng, J, Yuan, X, Gan, L, Lu, Z, and Xiong, R
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SPIN transfer torque , *MAGNETIC tunnelling , *MAGNETIZATION , *SPIN polarization - Abstract
A new writing scheme with a unidirectional pulse current is proposed for spin transfer torque (STT) based magnetic random-access memory (MRAM). To investigate the feasibility of the writing scheme, bilayered nano-pillars composed of a soft layer with small in-plane shape anisotropy and a hard layer with either large perpendicular anisotropy (PMA) or in-plane anisotropy (IMA) are designed and their switching behaviors are studied. It is found that in either type of bilayered nano-pillars, with the aid of the attached hard layer, the magnetization of the soft layer can be switched back and forth under a unidirectional pulse current. In an IMA/IMA nano-pillar, the magnetization of the free layer (FL) can achieve excellent alignment, which is in contrast to the IMA/PMA nano-pillar. By optimizing the dimensions and magnetic parameters of the IMA/IMA nano-pillar, a decently low switching current density (4.3Â Ă—Â 1011 A mâ'2) and ultrashort switching time (<1 ns) can be reached. Based on these results, the unidirectional writing scheme is practical if an IMA/IMA bilayer is used to replace the FL in a magnetic tunnel junction. Considering that a unidirectional writing scheme can enable the application of materials with high spin polarization such as half metals, and avoid the injection of writing current into junction using a special design, it may be very promising for STT-MRAM. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
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19. Contribution of inter-valley scattering in governing the steady state optical spin orientation in AlxGa1−xAs.
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Mudi, Priyabrata, Khamari, Shailesh K, and Sharma, T K
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ELECTRON spin states , *QUANTUM wells , *POLARIZED electrons , *SPIN polarization , *ELECTRON spin , *CIRCULAR polarization - Abstract
The impact of inter-valley scattering in modifying the density of optically injected spin polarized electrons in AlxGa1−xAs/GaAs heterostructure is investigated. Polarization resolved photoluminescence excitation measurements are performed for studying the spectral dependence of degree of circular polarization (DCP) of photoluminescence signal emanating from an adjacent quantum well layer. The experimental DCP spectra is found to deviate from the theoretically calculated curve at high excitation energy and the deviation is seen to widen with the Al-content of AlxGa1−xAs barrier layer. In the past, researchers had attributed similar deviations to the Dyakonov–Perel (DP) spin relaxation mechanism which dominates the electrons spin dynamics at high excitation energy. However, we find that the inter-valley scattering along with the DP mechanism decide the shape of optical spin orientation spectra at higher energy. In fact, at higher Al-content, the inter-valley scattering in AlxGa1–xAs layer becomes the most dominant mechanism to govern the steady state electron spin polarization at the band edge. A numerical model is also proposed for estimating the steady state electron spin polarization at zone centre by including the inter-valley scattering, energy relaxation and DP spin relaxation mechanisms. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
20. Carrier localization and magnetoresistance in DNA-functionalized carbon nanotubes.
- Author
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Rahman, Md Wazedur, Firouzeh, Seyedamin, and Pramanik, Sandipan
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MAGNETORESISTANCE , *SPIN polarization , *MAGNITUDE (Mathematics) , *SPIN valves - Abstract
Helical functionalization of carbon nanotubes using DNA strands can polarize carrier spins through chirality induced spin selectivity (or CISS) effect. Detection of this effect using transport experiments unravels an underlying magnetoresistance effect, origin of which is not well understood. In the present study, we investigate this effect, a fundamental understanding of which is crucial for the potential use of this system in spintronic devices. The conduction mechanism has been found to be in the strongly localized regime due to DNA functionalization, with the observed magnetoresistance originating from the interference effects between the forward and backward hopping paths. CISS-induced spin polarization has been estimated to increase the carrier localization length by an order of magnitude in the low temperature range and it affects the magnetoresistance effect in a non-trivial way that is not observed in conventional systems. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
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21. Simultaneous perfect polarization of spin and valley using monolayer MoS2 modulated by light and spin Zeeman field.
- Author
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Liu, Boyao, Liu, Danna, Yuan, Ruiyang, and Guo, Yong
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SPIN polarization , *SPINTRONICS - Abstract
Perfect polarization of spin and valley is found to coexist in the proposed junction of monolayer MoS2. The junction consists of two barriers modulated by off-resonant circularly polarized light and spin Zeeman field, respectively. By appropriately altering the modulation, we can achieve all four combinations of simultaneous perfect spin and valley polarization, which are , , , and. Moreover, we have found that by continuously tuning the light illuminating the junction, the valley polarization will abruptly dive from 100% to −100%. The spin polarization exhibits similar features when we tune the spin Zeeman field. Thus, the valley switching effect and the spin switching effect are realized in monolayer MoS2 by varying the circularly polarized light and spin Zeeman field. These results demonstrate the modulated monolayer MoS2's potential as a vital tool in spintronics and valleytronics. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
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22. Negative tunnel magnetoresistance in a quantum dot induced by interplay of a Majorana fermion and thermal-driven ferromagnetic leads.
- Author
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Niu, Peng-Bin, Cui, Bo-Xiang, and Luo, Hong-Gang
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TUNNEL magnetoresistance , *MAJORANA fermions , *QUANTUM dots , *SPIN polarization , *SUPERCONDUCTORS - Abstract
We investigate the spin-related currents and tunnel magnetoresistance through a quantum dot, which is side-coupled with a Majorana fermion zero mode and two thermal-driven ferromagnetic electrodes. It is found that the interplay of Majorana fermion and electrodes' spin polarization can induce a nonlinear thermal-bias spin current. This interplay also decreases the total magnitude of spin or charge current, in either parallel or antiparallel configuration. In addition, a thermal-driven negative tunnel magnetoresistance is found, which is an unique feature to characterize Majorana fermion. With large temperature difference, a step phenomenon is observed in gate tuned spin-up current. When the coupling between quantum dot and topological superconductor is strong enough, this step will evolve into a linear relation, revealing Majorana fermion's robustness. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
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23. Band structures of RE2O3:Eu (RE = Lu, Y, Sc) from perspective of spin-polarized quasi-particle approximation.
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Chen, ShiJie, Xie, Yaoping, Feng, He, and Guo, Haibo
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RARE earth oxides , *ELECTRON traps , *CONDUCTION bands , *SPIN polarization , *DENSITY functional theory - Abstract
Eu-doped rare earth sesquioxides RE2O3:Eu (RE = Lu, Y, Sc) exhibit subtle difference in scintillation processes, for which impurity levels play an important role but are difficult to assess computationally due to localized f-electrons and itinerant spd-electrons in the materials. Unpaired electrons of dopant Eu3+ ions also render complexity to these systems. In this study we calculated band structures of pure and Eu-doped RE2O3 using quasi-particle GW approximation with collinear spin polarization based on density functional theory. The band structures were similar across the three host material systems, varying with spin component and dopant's lattice site. Only the majority-spin states are responsible for the scintillation process, whereas the minority-spin states are entangled with the hosts' low-energy conduction bands. The materials' afterglow behavior was explained in terms of the positions of 4f orbitals and electron traps, as well as thermodynamics of the doping systems. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
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24. Enhanced exciton binding energy, Zeeman splitting and spin polarization in hybrid layered nanosheets comprised of (Cd, Mn)Se and nitrogen-doped graphene oxide: implication for semiconductor devices.
- Author
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Halder, Oindrila, Mallik, Gyanadeep, Suffczyński, Jan, Pacuski, Wojciech, Varadwaj, Kumar Shidhartha K, Satpati, Biswarup, and Rath, Satchidananda
- Subjects
- *
NANOSTRUCTURED materials , *SPIN polarization , *SEMICONDUCTOR devices , *BINDING energy , *GRAPHENE oxide , *MAGNETIC fields - Abstract
The exciton properties of (Cd,Mn)Se-NrGO (nitrogen doped reduced graphene oxide) hybrid layered nanosheets have been studied in a magnetic field up to 10 T and compared to those of (Cd,Mn)Se nanosheets. The temperature dependent photoluminescence reveals the hybridization of inter-band exciton and intra-center Mn transition with enhancement of the binding energy of exciton-Mn hybridized state (80 meV with respect to 60 meV in (Cd,Mn)Se nanosheets) and increase of exciton—phonon coupling strength to 90 meV (with respect to 55 meV in (Cd,Mn)Se nanosheets). The circularly polarized magneto—photoluminescence at 2 K provides evidence for magnetic field induced exciton spin polarization and the realization of excitonic giant Zeeman splitting with geff as high as 165.4 ± 10.3, much larger than in the case of (Cd,Mn)Se nanosheets (63.9 ± 6.6), promising for implementation in spin active semiconductor devices. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
25. Characterising a tunable, pulsed atomic beam using matter-wave interferometry.
- Author
-
Morley, J, Flack, R, Hiley, B J, and Barker, P F
- Subjects
- *
ATOMIC beams , *INTERFEROMETRY , *DE-Broglie waves , *SPIN polarization , *SILICON nitride , *VELOCITY - Abstract
We describe the creation and characterisation of a velocity tunable, spin-polarized beam of slow metastable argon atoms. We show that the beam velocity can be determined with a precision below 1% using matter-wave interferometry. The profile of the interference pattern was also used to determine the velocity spread of the beam, as well as the Van der Waals (VdW) co-efficient for the interaction between the metastable atoms and the multi-slit silicon nitride grating. The VdW co-efficient was determined to be C3 = 1.84 ± 0.17 a.u., in good agreement with values derived from spectroscopic data. Finally, the spin polarization of the beam produced during acceleration of the beam was also measured, demonstrating a spatially uniform spin polarization of 96% in the m = +2 state. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
26. Ferroelectric Controlled Spin Texture in Two-Dimensional NbOI2 Monolayer.
- Author
-
Ye, Qian, Shen, Yu-Hao, and Duan, Chun-Gang
- Subjects
- *
FERROELECTRIC polymers , *SPIN-orbit interactions , *SPIN polarization , *SPIN waves , *VECTOR spaces , *TEXTURES , *MONOMOLECULAR films - Abstract
The persistent spin helix (PSH) system is considered to have promising applications in energy-conservation spintronics because it supports an extraordinarily long spin lifetime of carriers. Here, we predict that the existence of PSH state in two-dimensional (2D) ferroelectric NbOI2 monolayers. Our first-principles calculation results show that there exists Dresselhaus-type spin-orbit coupling (SOC) band splitting near the conduction-band minimum (CBM) of the NbOI2 monolayer. It is revealed that the spin splitting near CBM merely refers to out-of-plane spin configuration in the wave vector space, which gives rise to a long-lived PSH state that can be controlled by reversible ferroelectric polarization. We believe that the coupling characteristics of ferroelectric polarization and spin texture in NbOI2 provide a platform for the realization of fully electric controlled spintronic devices. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
27. On the robustness of spin polarization for magnetic vortex accelerated proton bunches in density down-ramps.
- Author
-
Reichwein, L, Hützen, A, Büscher, M, and Pukhov, A
- Subjects
- *
SPIN polarization , *OPTICAL vortices , *PROTONS , *PROTON beams , *SPHEROMAKS , *DENSITY , *VECTOR beams - Abstract
We investigate the effect of density down-ramps on the acceleration of ions via magnetic vortex acceleration in a near-critical density gas target by means of particle-in-cell simulations. The spin-polarization of the accelerated protons is robust for a variety of ramp lengths at around 80%. Significant increase of the ramp length is accompanied by collimation of low-polarization protons into the final beam and large transverse spread of the highly polarized protons with respect to the direction of laser propagation. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
28. Spin and polarization effects on the nonlinear Breit–Wheeler pair production in laser-plasma interaction.
- Author
-
Song, Huai-Hang, Wang, Wei-Min, Li, Yan-Fei, Li, Bing-Jun, Li, Yu-Tong, Sheng, Zheng-Ming, Chen, Li-Ming, and Zhang, Jie
- Subjects
- *
PAIR production , *LASER-plasma interactions , *SPIN polarization , *MONTE Carlo method , *LASER pulses , *POLARIZED photons - Abstract
The spin effect of electrons/positrons (e−/e+) and polarization effect of γ photons are investigated in the interaction of two counter-propagating linearly polarized laser pulses of peak intensity 8.9 × 1023 W cm−2 with a thin foil target. The processes of nonlinear Compton scattering and nonlinear Breit–Wheeler pair production based on the spin- and polarization-resolved probabilities are implemented into the particle-in-cell (PIC) algorithm by Monte Carlo methods. It is found from PIC simulations that the average degree of linear polarization of emitted γ photons can exceed 50%. This polarization effect leads to a reduced positron yield by about 10%. At some medium positron energies, the reduction can reach 20%. Furthermore, we also observe that the local spin polarization of e−/e+ leads to a slight decrease of the positron yield about 2% and some anomalous phenomena about the positron spectrum and photon polarization at the high-energy range, due to spin-dependent photon emissions. Our results indicate that spin and polarization effects should be considered in calculating the pair production and laser-plasma interaction with the laser power of 10 PW to 100 PW classes. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
29. Speedup of nuclear spin diffusion in hyperpolarized solids.
- Author
-
Wang, Yu and Takeda, Kazuyuki
- Subjects
- *
NUCLEAR spin , *KIRKENDALL effect , *CORRECTION factors , *SPIN polarization , *DIFFUSION coefficients , *POLARIZATION (Nuclear physics) - Abstract
We propose a correction to the coefficient of nuclear spin diffusion by a factor , where is the average nuclear spin polarization. The correction, derived by extending the Lowe–Gade theory to low-temperature cases, implies that transportation of nuclear magnetization through nuclear spin diffusion accelerates when the system is hyperpolarized, whereas for low polarization the correction factor approaches unity and the diffusion coefficient coincides with the conventional diffusion coefficient valid in the high-temperature limit. The proposed scaling of the nuclear spin diffusion coefficient can lead to observable effects in the buildup of nuclear polarization by dynamic nuclear polarization. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
30. Generalized Rashba Coupling Approximation to a Resonant Spin Hall Effect of the Spin–Orbit Coupling System in a Magnetic Field.
- Author
-
Zhang, Rui, Biao, Yuan-Chuan, You, Wen-Long, Wang, Xiao-Guang, Zhang, Yu-Yu, and Hu, Zi-Xiang
- Subjects
- *
SPIN Hall effect , *SPIN-orbit interactions , *MAGNETIC fields , *TWO-dimensional electron gas , *SPIN polarization - Abstract
We introduce a generalized Rashba coupling approximation to analytically solve confined two-dimensional electron systems with both the Rashba and Dresselhaus spin–orbit couplings in an external magnetic field. A solvable Hamiltonian is obtained by performing a simple change of basis, which has the same form as that with only Rashba coupling. Each Landau state becomes a new displaced-Fock state instead of the original Harmonic oscillator Fock state. Analytical energies are consistent with the numerical ones in a wide range of coupling strength even for a strong Zeeman splitting, exhibiting the validity of the analytical approximation. By using the eigenstates, spin polarization correctly displays a jump at the energy-level crossing point, where the corresponding spin conductance exhibits a pronounced resonant peak. As the component of the Dresselhaus coupling increases, the resonant point shifts to a smaller value of the magnetic field. In contrast to pure Rashba couplings, we find that the Dresselhaus coupling and Zeeman splittings tend to suppress the resonant spin Hall effect. Our method provides an easy-to-implement analytical treatment to two-dimensional electron gas systems with both types of spin–orbit couplings by applying a magnetic field. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
31. Computational study of first-row transition metals in monodoped 4H-SiC.
- Author
-
Wolfe, Timothy S, Van Ginhoven, Renee M, and Strachan, Alejandro
- Subjects
- *
CRYSTAL field theory , *SEMICONDUCTOR devices , *SEMICONDUCTOR materials , *DENSITY of states , *SPIN polarization , *TRANSITION metals - Abstract
Electronic structure calculations of 4H-SiC doped with various transition metals reveal dilute magnetic semiconductor behavior in a material suitable for high-power and high-frequency semiconductor devices. Our results are consistent with prior work on V, Cr, and Mn doping and explore additional metals: Fe, Co, and Ni. Charge-state calculations show that the latter maintain amphoteric semi-insulating properties while offering a non-zero stable spin polarization and also greater asymmetry in the spin density of states than previously studied dopants. This indicates possible enhanced half-metal properties. Our results are consistent with crystal field theory, which helps interpret the observed spin states and assess the degree of charge localization and, subsequently, the range and strength of interactions relevant to ionization/capture and charge transport. These findings provide new avenues to tune the behavior of 4H-SiC for electronic device applications. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
32. Bias-controlled spin memory and spin injector scheme in the tunneling junction with a single-molecule magnet.
- Author
-
Zhang, Zheng-Zhong and Liu, Hao
- Subjects
- *
SINGLE molecule magnets , *INJECTORS , *MOLECULAR communication (Telecommunication) , *SPIN polarization , *COMPUTER storage devices , *MAGNETORESISTANCE , *SPIN valves , *MAGNETS - Abstract
A bias-controlled spin-filter and spin memory is theoretically proposed, which consists of the junction with a single-molecule magnet sandwiched between the nonmagnetic and ferromagnetic (FM) leads. By applying different voltage pulses Vwrite across the junction, the spin direction of the single-molecule magnet can be controlled to be parallel or anti-parallel to the magnetization of the FM lead, and the spin direction of SMM can be "read out" either by the magneto-resistance or by the spin current with another series of small voltage pulses Vprobe. It is shown that the polarization of the spin current is extremely high (up to 100%) and can be manipulated by the full-electric manner. This device scheme can be compatible with current technologies and has potential applications in high-density memory devices. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
33. Loops and polarization in strong-field QED.
- Author
-
Torgrimsson, Greger
- Subjects
- *
MUELLER calculus , *POLARIZED electrons , *SPIN polarization , *POLARIZED photons , *LASER pulses - Abstract
In a previous paper we showed how higher-order strong-field-QED processes in long laser pulses can be approximated by multiplying sequences of 'strong-field Mueller matrices'. We obtained expressions that are valid for arbitrary field shape and polarization. In this paper we derive practical approximations of these Mueller matrices in the locally-constant- and the locally-monochromatic-field regimes. The spin and polarization can also change due to loop contributions (the mass operator for electrons and the polarization operator for photons). We derive Mueller matrices for these as well, for arbitrary laser polarization and arbitrarily polarized initial and final particles. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
34. Effect of polarimetric nonregularity on the spin of three-dimensional polarization states.
- Author
-
Gil, José J, Friberg, Ari T, Norrman, Andreas, and Setälä, Tero
- Subjects
- *
SPIN polarization , *ELECTRIC fields - Abstract
While the spin of two-dimensional polarization states admits a simple representation, its physical interpretation for three-dimensional (3D) mixed polarization states requires a more involved analysis. In this work, we address the spin structure of the electric field of a general 3D polarization state by taking advantage of the characteristic decomposition and the recently introduced notion of nonregularity associated with 3D states. We show that a nonregular polarization state necessarily has an additional spin component due to the state's genuinely 3D nature, and both the orientation and magnitude of the spin are regulated by the degree of nonregularity. The results provide new physical insight into partially polarized evanescent and tightly focused light fields in which strong nonregular character has recently been demonstrated. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
35. Comparison of a direct measure of barrier crossing times with indirect measures such as the Larmor time.
- Author
-
Rivlin, Tom, Pollak, Eli, and Dumont, Randall S
- Subjects
- *
SPIN polarization , *POTENTIAL barrier , *TIME measurements , *WAVE packets - Abstract
Different approaches for considering barrier crossing times are analyzed, with special emphasis on recent experiments which attempt to measure what is commonly referred to as the Larmor tunneling time. We show that that these experiments cannot reveal the Larmor time, due to the finite energy width of the incident particles. The Larmor time, which measures changes in spin polarization, is classified together with other measurements such as the Buttiker–Landauer oscillating barrier time as indirect measurements of interaction times of scattered particles. In contrast, we present a direct quantum mechanical measure of a barrier crossing time taken to be the difference between the mean flight time for a particle transmitted through a potential barrier incident on a screen and the time it would take to reach the same screen without the barrier. These metrics are asymptotic, in the sense that they infer a time from a measurement after the scattering event is over, whereas other measures like the dwell time are local. Some time measures are well-defined only for incident states which are monochromatic in energy, others are well-defined also for incident wavepackets whose incident energy width is finite. In this paper we compare the different approaches to conclude that only the flight time can be used to answer the provocative (but ultimately ill-posed) question: how much time does it take to tunnel through a barrier? [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
36. Spin polarization in an ac-driven magnetic material with vanishing net magnetization: a new proposal.
- Author
-
Dey, Moumita, Sarkar, Manik, and Maiti, Santanu K
- Subjects
- *
MAGNETIC materials , *SPIN polarization , *GREEN'S functions , *MAGNETIZATION , *ELECTRIC fields - Abstract
In this work, we address the fundamental question of whether a magnetic material having zero net magnetization can produce polarized spin current from a completely unpolarized one. Common wisdom suggests that this is not possible, but if we break the symmetry in hopping integrals in different segments of the magnetic sample, then a finite possibility of getting polarized spin current is established. To substantiate this fact, we consider a one-dimensional magnetic chain with vanishing net magnetization where one part of the chain is subjected to an ac electric field, keeping the other part free. The ac field, introduced through Peierls substitution, modulates the hopping integrals yielding a misalignment of up and down spin channels, which is the primary requirement to get finite spin polarization. Simulating the system within a tight-binding framework, we compute spin-dependent transmission probabilities using the well-known Green's function prescriptionand determine junction currents following the Landauer–Büttiker formalism. Our analysis may shed some light on designing spin-polarized devices using driven magnetic materials with vanishing net magnetization. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
37. Interference traps waves in an open system: bound states in the continuum.
- Author
-
Sadreev, Almas F
- Subjects
- *
BOUND states , *CAVITY resonators , *SPIN polarization , *COUPLED mode theory (Wave-motion) , *RESONATORS , *RESONANCE - Abstract
I review the four mechanisms of bound states in the continuum (BICs) in the application of microwave and acoustic cavities open to directional waveguides. The most simple are symmetry-protected BICs, which are localized inside the cavity because of the orthogonality of the eigenmodes to the propagating modes of waveguides. However, the most general and interesting is the Friedrich–Wintgen mechanism, when the BICs are the result of the fully destructive interference of outgoing resonant modes. The third type of BICs, Fabry–Perot BICs, occurs in a double resonator system when each resonator can serve as an ideal mirror. Finally, the accidental BICs can be realized in the open cavities with no symmetry like the open Sinai billiard in which the eigenmode of the resonator can become orthogonal to the continuum of the waveguide accidentally due to a smooth deformation of the eigenmode. We also review the one-dimensional systems in which the BICs occur owing to the fully destructive interference of two waves separated by spin or polarization or by paths in the Aharonov–Bohm rings. We make broad use of the method of effective non-Hermitian Hamiltonian equivalent to the coupled mode theory, which detects BICs by finding zero-width resonances. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
38. Configuration of transition-metal atoms on iridium-doped graphene.
- Author
-
Han, Yan, Wan, Jian-Guo, Wan, Xiaodan, Chang, Yuan, Liu, Hongsheng, Gao, Junfeng, and Wang, Guang-Hou
- Subjects
- *
CONDUCTION electrons , *ATOMS , *GRAPHENE , *SPIN polarization , *CHARGE transfer , *THULIUM , *TRANSITION metals - Abstract
Our theoretical calculation and analysis show that the configuration of transition-metal (TM) atoms on iridium-doped graphene depends on the number of the d-state valence electrons of the TM atoms. TM atoms with three or less d-state valence electrons prefer to form a horizontal configuration and destroy the original C3v symmetry of the substrate. If there are more than three (but not five) d-state valence electrons in a TM atom, the TM atom selects the site just on the top of the iridium atoms and thus forms a vertical configuration, and the C3v symmetry of the iridium-doped graphene remains. For TM atoms with five d-state valence electrons and a closed s shell, the TM atoms and the iridium-doped graphene prefer to form an inclined configuration. The configuration regularity of the iridium-doped graphene-adsorbing TM atoms is attributed to the unique spin and orbital angular momentum of the electron in the iridium-doped graphene and the unique selection rule of the charge transfer under spin polarization. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
39. Corrigendum: high spin polarization in all-3d-metallic Heusler compounds: the case of Fe2CrZ and Co2CrZ (Z = Sc, Ti, V) (2019 J. Phys: D. Appl. Phys. 52 205003).
- Author
-
Özdoğan, Kemal, Maznichenko, Igor, Ostanin, Sergey, Şaşıoğlu, Ersoy, Ernst, Arthur, Mertig, Ingrid, and Galanakis, Iosif
- Subjects
- *
SPIN polarization , *HEUSLER alloys , *MATERIALS science , *CARBON dioxide , *UNIT cell - Published
- 2024
- Full Text
- View/download PDF
40. Strain Tunable Berry Curvature Dipole, Orbital Magnetization and Nonlinear Hall Effect in WSe2 Monolayer.
- Author
-
Qin, Mao-Sen, Zhu, Peng-Fei, Ye, Xing-Guo, Xu, Wen-Zheng, Song, Zhen-Hao, Liang, Jing, Liu, Kaihui, and Liao, Zhi-Min
- Subjects
- *
HALL effect , *ANOMALOUS Hall effect , *MAGNETIZATION , *CURVATURE , *EXCITON theory , *SPIN polarization , *SPEED of light - Abstract
The electronic topology is generally related to the Berry curvature, which can induce the anomalous Hall effect in time-reversal symmetry breaking systems. Intrinsic monolayer transition metal dichalcogenides possesses two nonequivalent K and K′ valleys, having Berry curvatures with opposite signs, and thus vanishing anomalous Hall effect in this system. Here we report the experimental realization of asymmetrical distribution of Berry curvature in a single valley in monolayer WSe2 via applying uniaxial strain to break C3v symmetry. As a result, although the Berry curvature itself is still opposite in K and K′ valleys, the two valleys would contribute equally to nonzero Berry curvature dipole. Upon applying electric field E , the emergent Berry curvature dipole D would lead to an out-of-plane orbital magnetization M ∝ D ⋅ E , which further induces an anomalous Hall effect with a linear response to E2, known as nonlinear Hall effect. We show the strain modulated transport properties of nonlinear Hall effect in monolayer WSe2 with moderate hole-doping by gating. The second-harmonic Hall signals show quadratic dependence on electric field, and the corresponding orbital magnetization per current density M/J can reach as large as 60. In contrast to the conventional Rashba–Edelstein effect with in-plane spin polarization, such current-induced orbital magnetization is along the out-of-plane direction, thus promising for high-efficient electrical switching of perpendicular magnetization. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
41. Fano Effect and Spin-Polarized Transport in a Triple-Quantum-Dot Interferometer Attached to Two Ferromagnetic Leads.
- Author
-
Bai, Jiyuan, Chen, Kongfa, Ren, Pengyu, Li, Jianghua, He, Zelong, and Li, Li
- Subjects
- *
FANO resonance , *GREEN'S functions , *SPIN polarization , *ELECTRON transport , *INTERFEROMETERS - Abstract
We report the conductance and average current through a triple-quantum-dot interferometer coupled with two ferromagnetic leads using the nonequilibrium Green's function. The results show that the interference between the resonant process and the non-resonant process leads to the formation of Fano resonance. More Fano resonances can be observed by applying a time-dependent external field. As a Zeeman magnetic field is applied, the spin-up electron transport is depressed in a certain range of electron energy levels. A spin-polarized pulse device can be realized by adjusting the spin polarization parameters of ferromagnetic leads. Moreover, the I–V characteristic curves show that under the influence of Fano resonance, the spin polarization is significantly enhanced by applying a relatively large reverse bias voltage. These results strongly suggest that the spin-polarized pulse device can be potentially applied as a spin-dependent quantum device. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
42. Geometric spin–orbit coupling and chirality-induced spin selectivity.
- Author
-
Shitade, Atsuo and Minamitani, Emi
- Subjects
- *
SPIN polarization , *CHIRALITY of nuclear particles , *CHIRALITY , *SPIN-orbit interactions - Abstract
We report a new type of spin–orbit coupling (SOC) called geometric SOC. Starting from the relativistic theory in curved space, we derive an effective nonrelativistic Hamiltonian in a generic curve embedded into flat three dimensions. The geometric SOC is O(m−1), in which m is the electron mass, and hence much larger than the conventional SOC of O(m−2). The energy scale is estimated to be a hundred meV for a nanoscale helix. We calculate the current-induced spin polarization in a coupled-helix model as a representative of the chirality-induced spin selectivity. We find that it depends on the chirality of the helix and is of the order of 0.01ℏ per nm when a charge current of 1 μA is applied. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
43. Superlattice-barrier magnetic tunnel junctions with half-metallic magnets.
- Author
-
Tseng, Peng, Chen, Zheng-Yi, and Hsueh, Wen-Jeng
- Subjects
- *
MAGNETIC tunnelling , *MAGNETIC control , *MAGNETS , *SPIN polarization , *MAGNESIUM oxide - Abstract
Spin-transfer torque (STT) applications in magnetization switching such as magnetic tunnel junctions (MTJs) have been of popular interest in the development of novel memory technologies. However, the high switching power associated with these is a critical disadvantage in the operation of typical magnesium oxide (MgO)-based STT-MTJs. In this study, an ultra-low switching power, only 10% of the MgO-based MTJs, is achieved by high-purity spin polarization current using a superlattice-barrier MTJ with half-metallic magnets. The resistance-area product of the device is reduced to 0.2 Ω μm2, which is less than 10% of that in traditional MgO-based MTJs. The proposed MTJ has a higher performance, including STT and required switching current. A decrease in the switching power could avoid not only the disadvantages of power dissipation but also the device endurance due to lower Joule heating in the proposed MTJs. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
44. Direct measurements of proximity induced spin polarization in 2D systems.
- Author
-
Gilbert, Simeon J and Dowben, Peter A
- Subjects
- *
SPIN polarization , *MAGNETIC coupling , *MONOMOLECULAR films , *MAGNETIZATION , *SEMICONDUCTORS - Abstract
Controlling the spin polarization of a 2D semiconductor through the proximity effect is an appealing approach for creating next generation spintronic devices; however, experiments showing the feasibility of this method are still limited. Here, we present a review of efforts intended to directly measure the spin polarization of monolayer graphene and h-BN coupled to a magnetic substrate. When considered together these studies conclusively show that 2D monolayers can obtain a spin polarization that is dependent on the magnetization of the underlying substrate, and, in some cases, can be comparable to the spin polarization of conventional ferromagnets. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
45. Temperature dependence of transport mechanisms in organic multiferroic tunnel junctions.
- Author
-
Xiao, Can, Sun, Huawei, Cheng, Luming, Devaux, Xavier, Ferri, Anthony, Huang, Weichuan, Desfeux, Rachel, Li, Xiao-Guang, Migot, Sylvie, Chshiev, Mairbek, Rauf, Sajid, Qi, Yajun, Wang, Ruilong, Zhang, Tianjin, Yang, Changping, Liang, Shiheng, and Lu, Yuan
- Subjects
- *
TUNNELS , *ELECTRON spin , *SPIN polarization , *DEPENDENCY (Psychology) , *TUNNEL junctions (Materials science) , *TEMPERATURE , *ELECTRON tunneling , *MULTIFERROIC materials - Abstract
Organic multiferroic tunnel junctions (OMFTJs) with multi-resistance states have been proposed and have drawn intensive interests due to their potential applications, for example in memristor and spintronics based synapse devices. The ferroelectric control of spin polarization at a ferromagnet/ferroelectric organic (FE-Org) interface by electrically switching the ferroelectric polarization of the FE-Org has been recently realized. However, there is still a lack of understanding of the transport properties in OMFTJs, especially the interplay between the ferroelectric domain structure in the organic barrier and the spin polarized electron tunneling through the barrier. Here, we report on a systematic study of the temperature dependent transport behavior in La0.6Sr0.4MnO3/PVDF/Co OMFTJs. It is found that thermal fluctuation of the ferroelectric domains play an important role on the transport properties. When T > 120 K, the opposite temperature dependence of resistance for up and down ferroelectric polarization states results in a rapid diminishing of the tunneling electroresistance. These results contribute to the understanding of the transport properties for designing high performance OMFTJs for memristor and spintronics applications. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
46. The CPT-violating effects on neutrons' gravitational bound state.
- Author
-
Xiao, Zhi and Shao, Lijing
- Subjects
- *
BOUND states , *NEUTRONS , *SPIN polarization , *ANALYTICAL solutions , *EQUIVALENCE principle (Physics) - Abstract
In this work, the CPT-violating (CPTV) interactions on neutrons' gravitational bound state are studied. With simple analytical solutions, we provide a preliminary investigation into the Lorentz-violation (LV)-induced spin precession due to the and couplings, where and represent LV coefficients. The helicity-dependent couplings can induce unusual phase evolutions with position and momentum dependence. As varies with time due to the Earth's motion, the spin polarization also shows a sidereal time dependence, and it may be enhanced with time for an ultra-stable polarized state of neutrons. The inseparability of the spin-momentum coupling of the term can also lead to a motional-dependent polarization state. With precisely measured transition frequency between different gravitational bound states, we get a rough bound GeV for unpolarized neutrons. If the spin-flip transition frequency can reach comparable precision in the future, the bound could be improved to the level of 10−24 GeV. The test of weak equivalence principle with polarized atoms may also improve it significantly. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
47. Theory of the inverse Faraday effect due to the Rashba spin–oribt interactions: roles of band dispersions and Fermi surfaces.
- Author
-
Tanaka, Yasuhiro, Inoue, Takashi, and Mochizuki, Masahito
- Subjects
- *
FARADAY effect , *FERMI surfaces , *RASHBA effect , *TIME-dependent Schrodinger equations , *SPIN polarization , *ELECTRON spin , *MAGNETOOPTICS - Abstract
We theoretically study the inverse Faraday effect, i.e., the optical induction of spin polarization with circularly polarized light, by particularly focusing on effects of band dispersions and Fermi surfaces in crystal systems with the spin–orbit interaction (SOI). By numerically solving the time-dependent Schrödinger equation of a tight-binding model with the Rashba-type SOI, we reproduce the light-induced spin polarization proportional to where E0 and ω are the electric-field amplitude and the angular frequency of light, respectively. This optical spin induction is attributed to dynamical magnetoelectric coupling between the light electric field and the electron spins mediated by the SOI. We elucidate that the magnitude and sign of the induced spin polarization sensitively depend on the electron filling. To understand these results, we construct an analytical theory based on the Floquet theorem. The theory successfully explains the dependencies on E0 and ω and ascribes the electron-filling dependence to a momentum-dependent effective magnetic field governed by the Fermi-surface geometry. Several candidate materials and experimental conditions relevant to our theory and model parameters are also discussed. Our findings will enable us to engineer the magneto-optical responses of matters via tuning the material parameters. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
48. Symmetry-Assisted Protection and Compensation of Hidden Spin Polarization in Centrosymmetric Systems.
- Author
-
Zhang, Yingjie, Liu, Pengfei, Sun, Hongyi, Zhao, Shixuan, Xu, Hu, and Liu, Qihang
- Subjects
- *
SPIN polarization , *SPIN-orbit interactions , *BRILLOUIN zones , *RARE earth metals , *LUTETIUM compounds - Abstract
It was recently noted that in certain nonmagnetic centrosymmetric compounds, spin–orbit interactions couple each local sector that lacks inversion symmetry, leading to visible spin polarization effects in the real space, dubbed "hidden spin polarization (HSP)". However, observable spin polarization of a given local sector suffers interference from its inversion partner, impeding material realization and potential applications of HSP. Starting from a single-orbital tight-binding model, we propose a nontrivial way to obtain strong sector-projected spin texture through the vanishing hybridization between inversion partners protected by nonsymmorphic symmetry. The HSP effect is generally compensated by inversion partners near the Γ point but immune from the hopping effect around the boundary of the Brillouin zone. We further summarize 17 layer groups that support such symmetry-assisted HSP and identify hundreds of quasi-2D materials from the existing databases by first-principle calculations, among which a group of rare-earth compounds LnIO (Ln = Pr, Nd, Ho, Tm, and Lu) serves as great candidates showing strong Rashba- and Dresselhaus-type HSP. Our findings expand the material pool for potential spintronic applications and shed light on controlling HSP properties for emergent quantum phenomena. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
49. Two-dimensional hexagonal Zn3Si2 monolayer: Dirac cone material and Dirac half-metallic manipulation.
- Author
-
Guan, Yurou, Song, Lingling, Zhao, Hui, Du, Renjun, Liu, Liming, Yan, Cuixia, and Cai, Jinming
- Subjects
- *
BORON nitride , *DENSITY functionals , *MONOMOLECULAR films , *ELECTRON spin , *SPIN polarization , *POLARIZED electrons , *SPIN-orbit interactions , *EXCITON theory - Abstract
The fascinating Dirac cone in honeycomb graphene, which underlies many unique electronic properties, has inspired the vast endeavors on pursuing new two-dimensional (2D) Dirac materials. Based on the density functional theory method, a 2D material Zn3Si2 of honeycomb transition-metal silicide with intrinsic Dirac cones has been predicted. The Zn3Si2 monolayer is dynamically and thermodynamically stable under ambient conditions. Importantly, the Zn3Si2 monolayer is a room-temperature 2D Dirac material with a spin–orbit coupling energy gap of 1.2 meV, which has an intrinsic Dirac cone arising from the special hexagonal lattice structure. Hole doping leads to the spin polarization of the electron, which results in a Dirac half-metal feature with single-spin Dirac fermion. This novel stable 2D transition-metal-silicon-framework material holds promises for electronic device applications in spintronics. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
50. High-efficiency spin polarization in electron transport through the graphene nanoribbon coupled to chromium triiodide.
- Author
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Han, Xiao, Zheng, Tian-Fang, Jiang, Cui, Li, Lin, and Gong, Wei-Jiang
- Subjects
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POLARIZED electrons , *ELECTRON spin , *SPIN polarization , *ELECTRON transport , *GRAPHENE , *CHROMIUM - Abstract
Spin-polarized electron transport through the zigzag graphene nanoribbon (ZGNR) is investigated by assuming that it couples with different charomium triiodide (CrI3) geometries, respectively. That is to say that the ZGNR either absorbs the monolayer CrI3 or one CrI3 molecule, or couples laterally with one CrI3 molecule. It is found that the spin polarization in the electron transport process is tightly dependent on the CrI3 geometry and the ZGNR-CrI3 coupling manner. When the CrI3 molecule is absorbed on the surface of the ZGNR, the spin-polarization efficiency is much higher than the other two cases, accompanied by the wide spin-polarization region. This work provides a new kind of scheme for optimizing the spin polarization in graphene-based materials. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
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