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Electron transport through a variety of helical structures has been shown to exhibit high-efficiency spin filtering, which is called chirality-induced spin selectivity (CISS). In this paper, we consider a helical chain of atomic p orbitals, which has been employed as a model in exploring the mechanism of CISS in previous theories, and show that the interatomic hopping along the helical chain induces an effective magnetic field (EMF) acting on the atomic orbital angular momentum (OAM). In chains where the curvature and torsion of the helix are small, we find that the EMF on the binormal component of the atomic OAM is created by the curvature, while that on the tangential component is produced by the torsion. We show that such coupling of the atomic OAM and the interatomic hopping leads to current-induced orbital and spin polarizations. We expect that the present coupling, which is expressed locally, can be used to estimate orbital and spin polarizations locally induced in molecules and solids. [ABSTRACT FROM AUTHOR]

The control of electron spin, crucial to the stability of matter, offers new possibilities for manipulating the properties of molecules and materials with potential applications in spintronics and chemical reactions. Recent experiments have demonstrated that electron transmission through chiral molecules depends on the electron spin orientation, a phenomenon known as chiral-induced spin selectivity (CISS). In this study, we show that CISS can be observed in achiral systems driven by an external circularly polarized laser field in the framework of Floquet engineering. By using the Floquet theory for a time-periodically driven system to investigate spin-dependent electron transport in a two-terminal setup, we demonstrate that the spin polarization can approach unity if the light intensity is sufficiently strong, the rate of dephasing is sufficiently low, and the average chemical potential of the two leads is within an appropriate range of values, which is narrow because of the high frequency of the laser field. To obtain a broader range of energies for large spin polarization, a combination of chiral molecules and light–matter interactions is considered, and the spin polarization of electrons transported through a helical molecule driven by a laser field is evaluated. [ABSTRACT FROM AUTHOR]

Different from conventional ferromagnetic methods, producing a spin-polarized current through electrical ways in spintronic devices can greatly increase operating speed, reduce power consumption, and improve device integration. Inspired by recent experimental progress on the synthesis of a heptauthrene molecule, we investigate its spin-dependent transport contacted with Au electrodes through first-principles calculations. By applying a gate voltage, the transmission can be switched between completely spin-up and spin-down polarized states, achieving an electrically controlled dual-spin filter. Furthermore, a fine tuning on the spin polarization, between 100% and − 100%, can also be realized, where the transport with any ratio of spin-up to spin-down electron quantities can be realized beyond the traditional devices. The peculiar transmission spectra and their shift are found to play crucial roles, where transmission peaks distribute on both sides of the Fermi level with opposite spin components. Such a spin-polarization modulating effect is found to be robust to the molecule-electrode contacting site, indicating it is an intrinsic feature of such systems. Moreover, the dimension of the device is at the single-molecule level, suggesting great application potential. [ABSTRACT FROM AUTHOR]

In this paper, we have explored the electronic and magnetic properties of MS2(M = Co , Ni) using first-principles calculations. Our data show rather high tunability of the electronic and magnetic properties of the alloy Co 1 − x NixS2 (0. 0 ≤ x ≤ 1. 0) with the emergence of half-metallicity that persisted up to the intermediate doping concentration. The half-metallic ground state is characterized by large spin polarization at the Fermi level ( E F ). Beyond the critical doping concentration x ∼ 0. 6 , we obtained a metallic solution followed by an antiferromagnetic ground state at a larger doping concentration. This study provides the underlying physics to understand the low-energy Hilbert space and reports the role of the Fermi surface in controlling the electron transport and thus elucidating the anomalous electronic and magnetic behavior of Co 1 − x NixS2. [ABSTRACT FROM AUTHOR]

Periodic nanostructure is a novel method to manipulate the electronic properties in electronics. An efficient method in this paper is proposed to judge whether m identical periods' magnetic nanostructure is a periodic structure by judging whether its physical structure and its magnetic vector potential structure both keep periodic. By investigating the influence of the δ -doping potential on the electron transport properties with m identical periods' magnetic barrier nanostructure of InAs system, it shows that, firstly, the resonant peak of transmission probability, conductance, and spin polarization has been induced by splitting into (2 m − 1) folds with m units nanostructure, respectively, especially when the resonant peak of transmission probability is almost close to 1 as the incident energy is lower; secondly, the height of δ -doping potential has an extensive influence on the resonant peak of transmission probability, which the resonant peak will be more dependent of the height of δ -doping potential increasing. Meanwhile, the conductance will be decreased with the height of δ -doping potential increasing. [ABSTRACT FROM AUTHOR]

Recently, the long-range spin-selective transport in chiral molecules has been investigated for bio-spintronics. The experimental results for a natural metalloprotein molecule suggested a high spin selectivity. I performed first-principle calculations of electron spin transport in a natural metalloprotein molecule based on the Landauer formula. A gold–metalloprotein–gold device model was used to confirm the high spin polarization. There was a relatively large spin density at some amide groups in the helical peptide structures. Furthermore, a large spin density of iron atoms enhanced the spin density of the neighboring coordinated atoms, resulting in spin polarization in the whole molecule. [ABSTRACT FROM AUTHOR]

The chiral‐induced spin selectivity (CISS) effect relates to the spin‐selective electron transport through chiral molecules; therefore, the chiral molecules act as spin filters. In past studies, correlation was found between the magnitude of the spin filtering and the intensity of the circular dichroism (CD) spectrum (the first Compton peak) of the molecules. Since the intensity of the CD peak relates to both the magnitude of the electric and magnetic dipole transitions, it was not clear which of these properties correlate with the CISS effect. This work aims at addressing this question. By studying the spin‐dependent conduction and the CD spectra of the thiol‐functionalized enantiopure binaphthalene (BINAP) and ternaphthalene (TERNAP), we found that both BINAP and TERNAP exhibit a similar spin polarization of 50%, despite the first Compton peak in TERNAP being almost twice as intense as the peak in BINAP. These results can be explained by the similar values of their anisotropy (or dissymmetry) factor, gabs, which is proportional to the magnetic transition dipole moment. Hence, we concluded that the CISS effect is proportional to the transition dipole moment in chiral molecules, namely, to the dissymmetry factor. [ABSTRACT FROM AUTHOR]

The photon-assisted electron transport properties through a parallel-coupled tri-quantum-dot system are studied using the time-dependent non-equilibrium Green's function theory. When a time-dependent external field irradiates a parallel-coupled three-quantum-dot system, the interaction between photons and electrons provides more novel transport characteristics. The average current can be switched between zero and non-zero by controlling the level of the time-dependent external field, indicating that an optically-controlled quantum switch can be realized. The time-dependent external field makes it more advantageous for the system to be designed as a magnetic-controlled quantum switch. If the magnetic flux and Rashba spin orbit coupling interaction are simultaneously considered, the average current exhibits a spin polarization phenomenon. For the spin down current, the bound states are formed as the magnetic flux takes an appropriate value, which greatly enhances the spin polarization. These research results are expected to contribute to the design of future quantum function devices. [ABSTRACT FROM AUTHOR]

The spin polarization of current plays an important role in the performance of spintronic devices. Therefore, a highly spin-polarized current source has always been explored through various methods. We study the effects of magnetic order on the electronic structures of antiferromagnetic (AFM) MnBi 2 Te 4 films. A significant spin splitting is found in the surface states of a AFM MnBi 2 Te 4 film with three septuple layers (SLs). The AFM film can show typical metallic behavior for spin-down electrons, and exhibit a semiconductor or insulator behavior with a band gap at the Fermi level for spin-up electrons, just like semimetal ferromagnets with theoretical spin polarization up to 100%. We also study that the electron transport in the 3-SLs AFM film with a square potential barrier, we find a highly spin-polarized current can be switched on and off by modulating the barrier height in the film. • 3-SLs AFM film exhibits a semimetal ferromagnets behavior. • A highly spin-polarized current can be switched on and off by modulating the barrier height. • Gapless surface states induced by magnetic order. • Large spin splitting in spin splitting. [ABSTRACT FROM AUTHOR]

Half‐metallic materials are theoretically predicted to be metallic and insulating, which have not been confirmed experimentally, and the predictions are still in doubt. We report the resistance‐chiral anisotropy (R‐ChA), i.e. chirality‐dependent electrical conductivity, in chiral mesostructured Fe3O4 films (CMFFs) grown on the substrates via a hydrothermal method using amino acids as symmetry‐breaking agents. Two levels of chirality exist in the CMFFs: primary distortion of the crystal lattice forms twisted nanoflakes, and secondary helical stacking of nanoflakes forms fan‐shaped nanoplates. At temperatures below 30 K, the CMFFs exhibited metallic conductivity and insulation for one handedness and the other, respectively. The chirality‐dependent effective magnetic fields were speculated to stabilize the opposite spin in the antipodal chiral frame, which led to the free transport of electrons in one handedness of the chiral structure and immobility for the other handedness. [ABSTRACT FROM AUTHOR]

Half‐metallic materials are theoretically predicted to be metallic and insulating, which have not been confirmed experimentally, and the predictions are still in doubt. We report the resistance‐chiral anisotropy (R‐ChA), i.e. chirality‐dependent electrical conductivity, in chiral mesostructured Fe3O4 films (CMFFs) grown on the substrates via a hydrothermal method using amino acids as symmetry‐breaking agents. Two levels of chirality exist in the CMFFs: primary distortion of the crystal lattice forms twisted nanoflakes, and secondary helical stacking of nanoflakes forms fan‐shaped nanoplates. At temperatures below 30 K, the CMFFs exhibited metallic conductivity and insulation for one handedness and the other, respectively. The chirality‐dependent effective magnetic fields were speculated to stabilize the opposite spin in the antipodal chiral frame, which led to the free transport of electrons in one handedness of the chiral structure and immobility for the other handedness. [ABSTRACT FROM AUTHOR]

The introduction of external magnetic field is one of the most widely studied strategies for photogenerated carrier separation in recent years. However, magnetic materials have great disadvantages in terms of photocatalytic performance. Semiconductor materials with magnetic properties are also extremely rare. It is extremely peculiar to research the magnetism of semiconductor photocatalyst triggered by vacancy. Here, the first example of ferromagnetic Bi 2 S 3 is achieved by controlled Bi vacancy (Bi 2 S 3 -V Bi). The magnetism properties depends largely on the spin polarization of p electrons in S atoms, and its magnetic moment is mainly distributed on S atoms around cation vacancies. Under the induction of external magnetic field, the tunneling of spin-polarized electrons in S-2p orbital makes Bi 2 S 3 -V Bi have negative magnetoresistance effect. The ferromagnetic arrangement of Bi 2 S 3 -V Bi particles can reduce the resistivity and increase the tunneling of electrons. Meanwhile, Lorentz force generated by external magnetic field acts reversely on photogenerated electrons and holes, thus effectively inhibiting the recombination of carriers in photocatalyst. Moreover, the influence of Bi vacancy on Bi 2 S 3 magnetism is investigated by DFT calculation. This study provides a new strategy for effective carrier separation in photocatalysis. Schematic diagram of photocatalytic reaction mechanism induced by negative magnetoresistance effect and Lorentz force. [Display omitted] • For the first time, the introduction of Bi vacancy makes Bi 2 S 3 ferromagnetic. • Bi 2 S 3 -V Bi nanoparticles tunneling can induce negative magnetoresistance effect. • Under the action of external magnetic field, Lorentz force inhibits the separation of photogenerated carriers. • The hydrogen production rate of CdS/Bi 2 S 3 -V Bi reaches 9.93 mmol g−1 h−1 and has excellent cycle stability. [ABSTRACT FROM AUTHOR]

We present a theoretically investigation about the electron transport through a single-barrier structures in HgTe/CdTe quantum wells (QWs) with inverted band structure. For HgTe/CdTe QWs structure, the transmission probabilities show great dependence on the Rashba spin–orbit interaction (RSOI), the incident angle, the incident Fermi energy and the electric modulation potential. By tuning the modulation amplitude with gate voltage or the strength of RSOI modulation, the efficient spin-polarized P Z = 1 is achieved, which is formed due to the spin-split in band spectrum induced by the RSOI modulation. This electric mechanism provides us a way to manipulate the spin polarization electrically and convenient for experimental verification. [ABSTRACT FROM AUTHOR]

We present a theoretically investigation about the electron transport through a single-barrier structures in HgTe/CdTe quantum wells (QWs) with inverted band structure. For HgTe/CdTe QWs structure, the transmission probabilities show great dependence on the Rashba spin–orbit interaction (RSOI), the incident angle, the incident Fermi energy and the electric modulation potential. By tuning the modulation amplitude with gate voltage or the strength of RSOI modulation, the efficient spin-polarized P Z = 1 is achieved, which is formed due to the spin-split in band spectrum induced by the RSOI modulation. This electric mechanism provides us a way to manipulate the spin polarization electrically and convenient for experimental verification. [ABSTRACT FROM AUTHOR]

CoSi single crystal is a known realization of a chiral topological semimetal with simultaneously broken mirror and inversion symmetries. In addition to the symmetry-induced spin–orbit coupling, surface ferromagnetism is known in nominally diamagnetic CoSi structures, which appears due to the distorted bonds and ordered vacancies near the surface. We experimentally investigate electron transport through a thin CoSi flake at high current density. Surprisingly, we demonstrate d V / d I (I) curves which are qualitatively similar to ones for ferromagnetic multilayers with characteristic d V / d I magnon peaks and unconventional magnetic field evolution of the peaks' positions. We understand these observations as a result of current-induced spin polarization due to the significant spin–orbit coupling in CoSi. Scattering of non-equilibrium spin-polarized carriers within the surface ferromagnetic layer is responsible for the precessing spin-wave excitations, so the observed magnon modes are the joint effect of surface ferromagnetism and spin–orbit coupling in a CoSi chiral topological semimetal. Thus, thin CoSi flakes behave as magnetic conductors with broken inversion symmetry, which is important for different spintronic phenomena. [ABSTRACT FROM AUTHOR]