Electronic analog of the electro‐optic modulator
TL;DR: In this article, an electron wave analog of the electro-optic light modulator is proposed, where magnetized contacts are used to preferentially inject and detect specific spin orientations.
Abstract: We propose an electron wave analog of the electro‐optic light modulator. The current modulation in the proposed structure arises from spin precession due to the spin‐orbit coupling in narrow‐gap semiconductors, while magnetized contacts are used to preferentially inject and detect specific spin orientations. This structure may exhibit significant current modulation despite multiple modes, elevated temperatures, or a large applied bias.
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TL;DR: This review describes a new paradigm of electronics based on the spin degree of freedom of the electron, which has the potential advantages of nonvolatility, increased data processing speed, decreased electric power consumption, and increased integration densities compared with conventional semiconductor devices.
Abstract: This review describes a new paradigm of electronics based on the spin degree of freedom of the electron. Either adding the spin degree of freedom to conventional charge-based electronic devices or using the spin alone has the potential advantages of nonvolatility, increased data processing speed, decreased electric power consumption, and increased integration densities compared with conventional semiconductor devices. To successfully incorporate spins into existing semiconductor technology, one has to resolve technical issues such as efficient injection, transport, control and manipulation, and detection of spin polarization as well as spin-polarized currents. Recent advances in new materials engineering hold the promise of realizing spintronic devices in the near future. We review the current state of the spin-based devices, efforts in new materials fabrication, issues in spin transport, and optical spin manipulation.
9,917 citations
TL;DR: Spintronics, or spin electronics, involves the study of active control and manipulation of spin degrees of freedom in solid-state systems as discussed by the authors, where the primary focus is on the basic physical principles underlying the generation of carrier spin polarization, spin dynamics, and spin-polarized transport.
Abstract: Spintronics, or spin electronics, involves the study of active control and manipulation of spin degrees of freedom in solid-state systems. This article reviews the current status of this subject, including both recent advances and well-established results. The primary focus is on the basic physical principles underlying the generation of carrier spin polarization, spin dynamics, and spin-polarized transport in semiconductors and metals. Spin transport differs from charge transport in that spin is a nonconserved quantity in solids due to spin-orbit and hyperfine coupling. The authors discuss in detail spin decoherence mechanisms in metals and semiconductors. Various theories of spin injection and spin-polarized transport are applied to hybrid structures relevant to spin-based devices and fundamental studies of materials properties. Experimental work is reviewed with the emphasis on projected applications, in which external electric and magnetic fields and illumination by light will be used to control spin and charge dynamics to create new functionalities not feasible or ineffective with conventional electronics.
9,158 citations
Cites methods from "Electronic analog of the electro‐op..."
...Let us illustrate the generic spintronic scheme on a prototypical device, the Datta-Das spin field-effect transistor (SFET; Datta and Das, 1990), depicted in Fig....
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...Direct spin injection from a ferromagnet into a 2D electron gas,68 motivated by the proposal of Datta and Das (1990), initially showed only small effects (Gardelis et al., 1999; Hammar et al., 1999; Lee et al., 1999), with DR/R;1%, or effects within the noise (Filip et al., 2000)....
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University of Cambridge1, Istituto Italiano di Tecnologia2, Lancaster University3, University of Manchester4, Catalan Institution for Research and Advanced Studies5, Technical University of Denmark6, Nokia7, University of Trento8, Queen Mary University of London9, fondazione bruno kessler10, Technische Universität München11, Polytechnic University of Milan12, Centre national de la recherche scientifique13, University of Trieste14, University of Ioannina15, University of Geneva16, Trinity College, Dublin17, Texas Instruments18, University of Paris19, Spanish National Research Council20, Leiden University21, Delft University of Technology22, University of Patras23, École Normale Supérieure24, Radboud University Nijmegen25, Nest Labs26, Airbus UK27, Seoul National University28, Yonsei University29, University of Oxford30, Chalmers University of Technology31, University of Groningen32, STMicroelectronics33, Chemnitz University of Technology34, Max Planck Society35, Aalto University36
TL;DR: An overview of the key aspects of graphene and related materials, ranging from fundamental research challenges to a variety of applications in a large number of sectors, highlighting the steps necessary to take GRMs from a state of raw potential to a point where they might revolutionize multiple industries are provided.
Abstract: We present the science and technology roadmap for graphene, related two-dimensional crystals, and hybrid systems, targeting an evolution in technology, that might lead to impacts and benefits reaching into most areas of society. This roadmap was developed within the framework of the European Graphene Flagship and outlines the main targets and research areas as best understood at the start of this ambitious project. We provide an overview of the key aspects of graphene and related materials (GRMs), ranging from fundamental research challenges to a variety of applications in a large number of sectors, highlighting the steps necessary to take GRMs from a state of raw potential to a point where they might revolutionize multiple industries. We also define an extensive list of acronyms in an effort to standardize the nomenclature in this emerging field.
2,560 citations
TL;DR: The authors are starting to see a new paradigm where magnetization dynamics and charge currents act on each other in nanostructured artificial materials, allowing faster, low-energy operations: spin electronics is on its way.
Abstract: Electrons have a charge and a spin, but until recently these were considered separately. In classical electronics, charges are moved by electric fields to transmit information and are stored in a capacitor to save it. In magnetic recording, magnetic fields have been used to read or write the information stored on the magnetization, which 'measures' the local orientation of spins in ferromagnets. The picture started to change in 1988, when the discovery of giant magnetoresistance opened the way to efficient control of charge transport through magnetization. The recent expansion of hard-disk recording owes much to this development. We are starting to see a new paradigm where magnetization dynamics and charge currents act on each other in nanostructured artificial materials. Ultimately, 'spin currents' could even replace charge currents for the transfer and treatment of information, allowing faster, low-energy operations: spin electronics is on its way.
2,191 citations
Cites background from "Electronic analog of the electro‐op..."
...The first proposition of this kind [18], despites recent progress in injecting spin polarization into semiconductors [124], has not yet achieved any practical realization....
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...The spin injection effect was also demonstrated for planar geometries [17], and proposed to realize 3-terminal devices such as the spin transistor [18]....
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TL;DR: Recent technical advances in the atomic-scale synthesis of oxide heterostructures have provided a fertile new ground for creating novel states at their interfaces, with characteristic feature is the reconstruction of the charge, spin and orbital states at interfaces on the nanometre scale.
Abstract: Recent technical advances in the atomic-scale synthesis of oxide heterostructures have provided a fertile new ground for creating novel states at their interfaces. Different symmetry constraints can be used to design structures exhibiting phenomena not found in the bulk constituents. A characteristic feature is the reconstruction of the charge, spin and orbital states at interfaces on the nanometre scale. Examples such as interface superconductivity, magneto-electric coupling, and the quantum Hall effect in oxide heterostructures are representative of the scientific and technological opportunities in this rapidly emerging field.
2,037 citations
Cites background from "Electronic analog of the electro‐op..."
...A representative heterostructure effect is the magneto-electric coupling in the spin transistor proposed by Datta and Da...
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References
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TL;DR: In this paper, the spin-orbit interaction Hamiltonian HSO = alpha ( sigma *k) was used to change the usual patterns of B-1-periodic oscillations; some oscillations are strongly suppressed due to the diminishing of the gaps between adjacent levels and new oscillations appear due to intersections of levels.
Abstract: Oscillatory effects in a strong magnetic field B and magnetic susceptibility are investigated, as applied to 2D systems, in which the twofold spin degeneracy is lifted by the spin-orbit-interaction Hamiltonian HSO= alpha ( sigma *k). nu . The term HSO is shown to change greatly the usual patterns of B-1-periodic oscillations; some oscillations are strongly suppressed due to the diminishing of the gaps between adjacent levels, and new oscillations appear due to intersections of levels.
2,390 citations
TL;DR: A new technique to measure conduction electron relaxation times is described, using nonequilibrium magnetization present in a paramagnetic metal can be detected as an open circuit voltage across an interface between the paramagnet and a ferromagnet.
Abstract: Microscopic models are presented to elucidate the concept of interfacial charge-spin coupling. At the interface between a ferromagnet and a paramagnet, the spin subbands are loosely coupled, an interfacial conductance may be defined for each, and a result of their inequivalence is that an electric current flowing from a ferromagnetic metal into a paramagnetic metal will be partially spin polarized, i.e., will have an associated current of magnetization. The inverse is also true; nonequilibrium magnetization present in a paramagnetic metal can be detected as an open circuit voltage across an interface between the paramagnet and a ferromagnet. Using this effect, a new technique to measure conduction electron relaxation times is described.
282 citations
TL;DR: This work shows for AlGaAs/GaAs heterostructures how this finite spin splitting at B=0 evolves from the Zeeman splitting for B\ensuremath{
e}0 and predicts a vanishingspin splitting at a finite -magnetic- field \char22{}, which depends on the electron concentration in the inversion layer.
Abstract: Spin splitting of subband states in semiconductor heterostructures at B=0 is ascribed to the inversion asymmetry--induced bulk ${\mathrm{k}}^{3}$ term, which dominates in large-gap materials, and to the interface spin-orbit or Rashba term, which becomes important in narrow-gap systems. We show for AlGaAs/GaAs heterostructures how this finite spin splitting at B=0 evolves from the Zeeman splitting for B\ensuremath{
e}0 and predict a vanishing spin splitting at a finite -magnetic- field ---, which depends on the electron concentration in the inversion layer.
278 citations
TL;DR: In this article, a theoretical study of quantum interference phenomena in a T-shaped semiconductor structure is presented, and the results resemble the well-known solutions for the electromagnetic field in waveguides with the main difference that penetration of the wave function of the electrons can be controlled by external voltages.
Abstract: A theoretical study of quantum interference phenomena in a T‐shaped semiconductor structure is presented. Transmission and reflection coefficients are computed by use of a tight‐binding Green function technique. As expected, the results resemble the well‐known solutions for the electromagnetic field in waveguides with the main difference that the penetration of the wave function of the electrons can be controlled by external voltages. We conclude that transistor action based on quantum interference should be observable in such structures, and we present general results for the functional dependences of the transmission coefficient which corresponds to a transconductance.
256 citations
TL;DR: In this paper, the splitting in zero magnetic field between the up-and down-spin electrons in a two-dimensional electron gas is obtained for a series of three different modulation-doped heterostructures with high electron densities.
Abstract: The splitting in zero magnetic field between the up- and down-spin electrons in a two-dimensional electron gas is obtained for a series of three different ${\mathrm{In}}_{x}{\mathrm{Ga}}_{1\ensuremath{-}x}\mathrm{As}/{\mathrm{In}}_{0.52}{\mathrm{Al}}_{0.48}\mathrm{As}$ modulation-doped heterostructures with high electron densities [${n}_{s}\ensuremath{\sim}(1.5\ensuremath{-}1.8)\ifmmode\times\else\texttimes\fi{}{10}^{12}$ ${\mathrm{cm}}^{\ensuremath{-}2}$]. We have observed a characteristic beating modulation in the amplitude of the Shubnikov-de Haas oscillations in this system and up to six nodes have been measured in the Shubnikov-de Haas data for magnetic fields in the range $0.15 \mathrm{T}lBl1.0 \mathrm{T}$. Analysis of these data indicates that one subband is primarily occupied and the two beating frequencies arise from a spin splitting of the lowest subband. A spin splitting of 1.5-2.5 meV as $B\ensuremath{\rightarrow}0$ is deduced from the data. For magnetic fields applied at an angle $\ensuremath{\theta}$ to the interface, the beat positions scale as $cos\ensuremath{\theta}$ for small angles but increase steeply after a critical angle.
217 citations