日本物理学会誌及びJournal of the Physical Society of Japanの月刊について

The isolation of graphene has triggered an avalanche of studies into the spin-dependent physical properties of this material, as well as graphene-based spintronic devices Here we review the experimental and theoretical state-of-art concerning spin injection and transport, defect-induced magnetic moments, spin-orbit coupling and spin relaxation in graphene Future research in graphene spintronics will need to address the development of applications such as spin transistors and spin logic devices, as well as exotic physical properties including topological states and proximity-induced phenomena in graphene and other 2D materials

Graphene Spintronics

We review the electronic properties of bilayer graphene, beginning with a description of the tight-binding model of bilayer graphene and the derivation of the effective Hamiltonian describing massive chiral quasiparticles in two parabolic bands at low energies. We take into account five tight-binding parameters of the Slonczewski–Weiss–McClure model of bulk graphite plus intra- and interlayer asymmetry between atomic sites which induce band gaps in the low-energy spectrum. The Hartree model of screening and band-gap opening due to interlayer asymmetry in the presence of external gates is presented. The tight-binding model is used to describe optical and transport properties including the integer quantum Hall effect, and we also discuss orbital magnetism, phonons and the influence of strain on electronic properties. We conclude with an overview of electronic interaction effects.

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The electronic properties of bilayer graphene.

This article reviews static and dynamic interfacial effects in magnetism, focusing on interfacially-driven magnetic effects and phenomena associated with spin-orbit coupling and intrinsic symmetry breaking at interfaces. It provides a historical background and literature survey, but focuses on recent progress, identifying the most exciting new scientific results and pointing to promising future research directions. It starts with an introduction and overview of how basic magnetic properties are affected by interfaces, then turns to a discussion of charge and spin transport through and near interfaces and how these can be used to control the properties of the magnetic layer. Important concepts include spin accumulation, spin currents, spin transfer torque, and spin pumping. An overview is provided to the current state of knowledge and existing review literature on interfacial effects such as exchange bias, exchange spring magnets, spin Hall effect, oxide heterostructures, and topological insulators. The article highlights recent discoveries of interface-induced magnetism and non-collinear spin textures, non-linear dynamics including spin torque transfer and magnetization reversal induced by interfaces, and interfacial effects in ultrafast magnetization processes.

https://link.aps.org/accepted/10.1103/RevModPhys.89.025006

Interface-induced phenomena in magnetism

A review of new developments in theoretical and experimental electronic-structure investigations of half-metallic ferromagnets (HMFs) is presented. Being semiconductors for one spin projection and metals for another, these substances are promising magnetic materials for applications in spintronics (i.e., spin-dependent electronics). Classification of HMFs by the peculiarities of their electronic structure and chemical bonding is discussed. The effects of electron-magnon interaction in HMFs and their manifestations in magnetic, spectral, thermodynamic, and transport properties are considered. Special attention is paid to the appearance of nonquasiparticle states in the energy gap, which provide an instructive example of essentially many-body features in the electronic structure. State-of-the-art electronic calculations for correlated d-systems are discussed, and results for specific HMFs (Heusler alloys, zinc-blende structure compounds, CrO2, and Fe3O4) are reviewed.

/pdf/half-metallic-ferromagnets-from-band-structure-to-many-body-1hrl8mp5lm.pdf

Half-metallic ferromagnets: From band structure to many-body effects

Adsorption of $\mathrm{C}{\mathrm{O}}_{2}$ on a semiconductor surface is a prerequisite for its photocatalytic reduction. Owing to superior photocorrosion resistance, nontoxicity, and suitable band-edge positions, $\mathrm{Ti}{\mathrm{O}}_{2}$ is considered to be the most efficient photocatalyst for facilitating redox reactions. However, due to the absence of adequate understanding of the mechanism of adsorption, the $\mathrm{C}{\mathrm{O}}_{2}$ conversion efficiency on $\mathrm{Ti}{\mathrm{O}}_{2}$ surfaces has not been maximized. While anatase $\mathrm{Ti}{\mathrm{O}}_{2}$ (101) is the most stable facet, the (001) surface is more reactive, and it has been experimentally shown that the stability can be reversed and a larger percentage (up to $\ensuremath{\sim}89%)$ of the (001) facet can be synthesized in the presence fluorine ions. Therefore, through density functional calculations we have investigated the $\mathrm{C}{\mathrm{O}}_{2}$ adsorption on $\mathrm{Ti}{\mathrm{O}}_{2}$ (001) surfaces. We have developed a three-state quantum-mechanical model that explains the mechanism of chemisorption, leading to the formation of a tridentate carbonate complex. The electronic structure analysis reveals that the $\mathrm{C}{\mathrm{O}}_{2}\text{\ensuremath{-}}\mathrm{Ti}{\mathrm{O}}_{2}$ interaction at the surface is uniaxial and long ranged, which gives rise to anisotropy in binding energy (BE). It negates the widely perceived one-to-one correspondence between coverage and BE and infers that the spatial distribution of $\mathrm{C}{\mathrm{O}}_{2}$ primarily determines the BE. A conceptual experiment is devised where the $\mathrm{C}{\mathrm{O}}_{2}$ concentration and flow direction can be controlled to tune the BE within a large window of $\ensuremath{\sim}1.5\phantom{\rule{0.16em}{0ex}}\mathrm{eV}$. The experiment also reveals that a maximum of $50%$ coverage can be achieved for chemisorption. In the presence of water, the activated carbonate complex forms a bicarbonate complex by overcoming a potential barrier of $\ensuremath{\sim}0.9\phantom{\rule{0.16em}{0ex}}\mathrm{eV}$.

Quantum-mechanical process of carbonate complex formation and large-scale anisotropy in the adsorption energy of C O 2 on anatase Ti O 2 (001) surface

Graphdiyne—A Two-Dimensional Cathode for Aluminum Dual-Ion Batteries with High Specific Capacity and Diffusivity

At base, creating better lithium-ion batteries is all about understanding the diffusion of Li${}^{+}$, particularly its reversible intercalation in materials like olivine phosphates. This study shows that for a given diffusion path for Li${}^{+}$, the forward and backward activation barriers can be manipulated simply by choosing the level of doping $x$ in LiFe${}_{1-x}{M}_{x}$PO${}_{4}$. This simple knob can tune three of the most important electrochemical parameters: diffusivity, operating voltage, and band gap. The insight from this study should also apply to other transition-metal oxide cathode materials.

Engineering Diffusivity and Operating Voltage in Lithium Iron Phosphate through Transition-Metal Doping

Artificial confinement of electrons by tailoring the layer thickness has turned out to be a powerful tool to harness control over competing phases in nano-layers of complex oxides. We investigate the effect of dimensionality on transport properties of d -electron–based heavy-fermion metal CaCu3 Ru4 O12 . Transport behavior evolves from metallic to localized regime upon reducing thickness and a metal-insulator transition is observed below 3 nm film thickness for which sheet resistance crosses , the quantum resistance in 2D. Magnetotransport study reveals a strong interplay between inelastic and spin-orbit scattering lengths upon reducing thickness, which results in weak-antilocalization (WAL) to weak-localization (WL) crossover in magnetoconductance.

Evidence for weak-antilocalization–weak-localization crossover and metal-insulator transition in CaCu3Ru4O12 thin films

Using ab initio density functional calculations, we have investigated the stability and electronic structure of pure and oxygen doped semiconducting Cu3N. The oxygen can be accommodated in the system without structural instability as the formation energy either decreases when oxygen substitutes nitrogen, or remains nearly same when oxygen occupies the interstitial position. The interstitial oxygen (OI) prefers to stabilize in the unusual charge neutral state and acts as an acceptor to make the system a p-type degenerate semiconductor. In this case the hole pockets are formed by the partially occupied OI-p states. On the other hand, oxygen substituting nitrogen (OS) stabilizes in its usual −2 charge state and acts as a donor to make the system an n-type degenerate semiconductor. The electron pockets are formed by the conducting Cu-p states. In the case of mixed doping, holes are gradually compensated by the donor electrons and an intrinsic gap is obtained for stoichiometry. Our calculations predict the nature of doping as well as optical band gap variation in experimentally synthesized copper oxynitride. While interstitial doping contracts the lattice and increases the substitutional doping increases both lattice size and Mixed doping reduces Additionally we show that a rare intra-atomic d–p optical absorption can be realized in the pristine Cu3N as the Fermi level lies in the gap between the Cu-d dominated anti-bonding valence state and Cu-p conducting state.

http://iopscience.iop.org/article/10.1088/2053-1591/3/6/065902/pdf

Birabar Nanda

Papers

Quantum-mechanical process of carbonate complex formation and large-scale anisotropy in the adsorption energy of C O 2 on anatase Ti O 2 (001) surface

Graphdiyne—A Two-Dimensional Cathode for Aluminum Dual-Ion Batteries with High Specific Capacity and Diffusivity

Engineering Diffusivity and Operating Voltage in Lithium Iron Phosphate through Transition-Metal Doping

Evidence for weak-antilocalization–weak-localization crossover and metal-insulator transition in CaCu3Ru4O12 thin films

Tailoring p- and n- type semiconductor through site selective oxygen doping in Cu3N: density functional studies