Topic
Spin-½
About: Spin-½ is a research topic. Over the lifetime, 40423 publications have been published within this topic receiving 796639 citations.
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TL;DR: In this paper, the authors discuss the general problem of spin transport in a nonmagnetic channel between source and drain, and show why the transformation of spin information into a large electrical signal has been more easily achieved with carbon nanotubes than with semiconductors, and how the situation could be improved in the later case.
Abstract: Injecting spins into a semiconductor channel and transforming the spin information into a significant electrical output signal is a long-standing problem in spintronics. This is the prerequisite of several concepts of spin transistor. In this paper, we discuss the general problem of spin transport in a nonmagnetic channel between source and drain. Two problems must be mastered: 1) In diffusive regime, the injection/extraction of a spin-polarized current into/from a semiconductor beyond the ballistic zone at the interface with a magnetic metal requires the insertion of a spin-dependent and large enough interface resistance. 2) In both the diffusive and ballistic regimes and whatever the metallic or semiconducting character of the source/drain, a small enough interface resistance is the condition to keep the dwell time shorter than the spin lifetime and, thus, to conserve the spin-accumulation-induced output signal at an optimum level (DeltaR/Rap1 or larger). Practically, the main difficulties come from the second condition. In our presentation of experimental results, we show why the transformation of spin information into a large electrical signal has been more easily achieved with carbon nanotubes than with semiconductors, and we discuss how the situation could be improved in the later case
141 citations
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TL;DR: The first transport experiment on Landau level splitting in TDS Cd3As2 single crystals under high magnetic fields is reported, suggesting the removal of spin degeneracy by breaking time reversal symmetry.
Abstract: Three-dimensional topological Dirac semimetals (TDSs) are a new kind of Dirac materials that exhibit linear energy dispersion in the bulk and can be viewed as three-dimensional graphene. It has been proposed that TDSs can be driven to other exotic phases like Weyl semimetals, topological insulators and topological superconductors by breaking certain symmetries. Here we report the first transport experiment on Landau level splitting in TDS Cd3As2 single crystals under high magnetic fields, suggesting the removal of spin degeneracy by breaking time reversal symmetry. The detected Berry phase develops an evident angular dependence and possesses a crossover from non-trivial to trivial state under high magnetic fields, a strong hint for a fierce competition between the orbit-coupled field strength and the field-generated mass term. Our results unveil the important role of symmetry breaking in TDSs and further demonstrate a feasible path to generate a Weyl semimetal phase by breaking time reversal symmetry.
141 citations
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TL;DR: In this paper, it was shown that the back-force of an electrically neutral magnet is a consequence of the relativistic corrections to the motion of the particles composing the magnet.
Abstract: Shockley and James have noted that an electrically neutral magnet whose moment is changing with time exerts a force on an electric charge of negligible velocity at a large distance from it, but that there is no obvious corresponding back-action of the charge on the magnet, although required by general considerations of the conservation of momentum. In the present paper, it is shown that the back-force is a consequence of the relativity corrections to the motion of the particles composing the magnet. The proof is given generally in terms of the relativistic theorem on the motion of the "center of energy" and explicitly in terms of a Lagrangian for a system of particles obtained many years ago by Darwin. The effect of spin is examined and found not to affect the action-reaction balance. In the Appendix, the properties of the center of energy are utilized to show how the Darwin Lagrangian should be modified when there are nonelectric classical forces acting between the particles of the magnet.
141 citations
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TL;DR: It is predicted that Dirac quasiparticles can be controlled by the spin-orbit torque reorientation of the Néel vector in an antiferromagnet and this concept verified by minimal model and density functional calculations in the CuMnAs semimetal antiferromaagnet can lead to a topological metal-insulator transition driven by the NÉel vector and to the topological anisotropic magnetoresistance.
Abstract: Spin orbitronics and Dirac quasiparticles are two fields of condensed matter physics initiated independently about a decade ago Here we predict that Dirac quasiparticles can be controlled by the spin-orbit torque reorientation of the Neel vector in an antiferromagnet Using CuMnAs as an example, we formulate symmetry criteria allowing for the coexistence of topological Dirac quasiparticles and Neel spin-orbit torques We identify the nonsymmorphic crystal symmetry protection of Dirac band crossings whose on and off switching is mediated by the Neel vector reorientation We predict that this concept verified by minimal model and density functional calculations in the CuMnAs semimetal antiferromagnet can lead to a topological metal-insulator transition driven by the Neel vector and to the topological anisotropic magnetoresistance
141 citations
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TL;DR: A theoretical model considering the different graphene regions of the authors' devices that explains the experimental data and develops a lower bound on the spin relaxation time and spin relaxation length for intrinsic graphene.
Abstract: We measure spin transport in high mobility suspended graphene (μ ≈ 10(5)cm(2)/(V s)), obtaining a (spin) diffusion coefficient of 0.1 m(2)/s and giving a lower bound on the spin relaxation time (τ(s) ≈ 150 ps) and spin relaxation length (λ(s) = 4.7 μm) for intrinsic graphene. We develop a theoretical model considering the different graphene regions of our devices that explains our experimental data.
141 citations