The compensated magnetic order and characteristic terahertz frequencies of antiferromagnetic materials make them promising candidates to develop a new class of robust, ultrafast spintronic devices. ...The manipulation of antiferromagnetic spin-waves in thin films is anticipated to lead to new exotic phenomena such as spin-superfluidity, requiring an efficient propagation of spin-waves in thin films. However, the reported decay length in thin films has so far been limited to a few nanometers. In this work, we achieve efficient spin-wave propagation over micrometer distances in thin films of the insulating antiferromagnet hematite with large magnetic domains while evidencing much shorter attenuation lengths in multidomain thin films. Through transport and magnetic imaging, we determine the role of the magnetic domain structure and spin-wave scattering at domain walls to govern the transport. We manipulate the spin transport by tailoring the domain configuration through field cycle training. For the appropriate crystalline orientation, zero-field spin transport is achieved across micrometers, as required for device integration.
Graphene is an ideal medium for long-distance spin communication in future spintronic technologies. So far, the prospect is limited by the smaller sizes of exfoliated graphene flakes and lower spin ...transport properties of large-area chemical vapour-deposited (CVD) graphene. Here we demonstrate a high spintronic performance in CVD graphene on SiO2/Si substrate at room temperature. We show pure spin transport and precession over long channel lengths extending up to 16 μm with a spin lifetime of 1.2 ns and a spin diffusion length ∼6 μm at room temperature. These spin parameters are up to six times higher than previous reports and highest at room temperature for any form of pristine graphene on industrial standard SiO2/Si substrates. Our detailed investigation reinforces the observed performance in CVD graphene over wafer scale and opens up new prospects for the development of lateral spin-based memory and logic applications.
•The one-dimensional devices with phosphorene electrodes present excellent spin-filtering effects.•The spin-up and spin-down currents can both be controlled to on or off states.•Interesting low-bias ...NDR effect with large PVR ratio can be found.•The spin transport properties are better than the performance of the devices constructed by Au or graphene electrodes.
Multiple-effect molecular devices have been constructed by single molecule magnet Mn(dmit)2 and phosphorene electrodes. First-principle quantum transport calculations show that the devices present excellent spin-filtering, spin-switching and negative differential resistance effects, which can be explained by the frontier molecular orbitals, the projected density of states and evolution of the transmission spectra. These excellent spin transport properties are better than the performance of the devices constructed by Au or graphene electrodes, which suggest that the one-dimensional devices with phosphorene electrodes are promising candidates for future applications of phosphorene-based multi-functional spintronics devices.
Two-dimensional hybrid organic–inorganic perovskites (2D-HOIPs) that form natural multiple quantum wells have attracted increased research interest due to their interesting physics and potential ...applications in optoelectronic devices. Recent studies have shown that spintronics applications can also be introduced to 2D-HOIPs upon integrating chiral organic ligands into the organic layers. Here we report spin-dependent photovoltaic and photogalvanic responses of optoelectronic devices based on chiral 2D-HOIPs, namely, (R-MBA)2PbI4 and (S-MBA)2PbI4. The out-of-plane photocurrent response in vertical photovoltaic devices exhibits ∼10% difference upon right and left circularly polarized light (CPL) excitation, which originates from selective spin transport through the chiral multilayers. In contrast, the in-plane photocurrent response generated by CPL excitation of planar photoconductive devices shows a typical response of chirality-induced circular photogalvanic effect that originates from the Rashba splitting in the electronic bands of these compounds. Our studies may lead to potential applications of chiral 2D-HOIPs in optoelectronic devices that are sensitive to the light helicity.
We show spin lifetimes of 12.6 ns and spin diffusion lengths as long as 30.5 μm in single layer graphene nonlocal spin transport devices at room temperature. This is accomplished by the fabrication ...of Co/MgO-electrodes on a Si/SiO2 substrate and the subsequent dry transfer of a graphene-hBN-stack on top of this electrode structure where a large hBN flake is needed in order to diminish the ingress of solvents along the hBN-to-substrate interface. Interestingly, long spin lifetimes are observed despite the fact that both conductive scanning force microscopy and contact resistance measurements reveal the existence of conducting pinholes throughout the MgO spin injection/detection barriers. Compared to previous devices, we observe an enhancement of the spin lifetime in single layer graphene by a factor of 6. We demonstrate that the spin lifetime does not depend on the contact resistance area products when comparing all bottom-up devices indicating that spin absorption at the contacts is not the predominant source for spin dephasing.
We address spin transport in the easy-axis Heisenberg spin chain subject to different integrability-breaking perturbations. We find subdiffusive spin transport characterized by dynamical exponent
= 4 ...up to a timescale parametrically long in the anisotropy. In the limit of infinite anisotropy, transport is subdiffusive at all times; for finite anisotropy, one eventually recovers diffusion at late times but with a diffusion constant independent of the strength of the perturbation and solely fixed by the value of the anisotropy. We provide numerical evidence for these findings, and we show how they can be understood in terms of the dynamical screening of the relevant quasiparticle excitations and effective dynamical constraints. Our results show that the diffusion constant of near-integrable diffusive spin chains is generically not perturbative in the integrability-breaking strength.
We study particle and spin transport in a single-mode quantum point contact, using a charge neutral, quantum degenerate Fermi gas with tunable, attractive interactions. This yields the spin and ...particle conductance of the point contact as a function of chemical potential or confinement. The measurements cover a regime from weak attraction, where quantized conductance is observed, to the resonantly interacting superfluid. Spin conductance exhibits a broad maximum when varying the chemical potential at moderate interactions, which signals the emergence of Cooper pairing. In contrast, the particle conductance is unexpectedly enhanced even before the gas is expected to turn into a superfluid, continuously rising from the plateau at 1/h for weak interactions to plateau-like features at nonuniversal values as high as 4/h for intermediate interactions. For strong interactions, the particle conductance plateaus disappear and the spin conductance gets suppressed, confirming the spin-insulating character of a superfluid. Our observations document the breakdown of universal conductance quantization as many-body correlations appear. The observed anomalous quantization challenges a Fermi liquid description of the normal phase, shedding new light on the nature of the strongly attractive Fermi gas.
A wide range of materials, like d-wave superconductors, graphene, and topological insulators, share a fundamental similarity: their low-energy fermionic excitations behave as massless Dirac particles ...rather than fermions obeying the usual Schrödinger Hamiltonian. This emergent behavior of Dirac fermions in condensed matter systems defines the unifying framework for a class of materials we call "Dirac materials." In order to establish this class of materials, we illustrate how Dirac fermions emerge in multiple entirely different condensed matter systems and we discuss how Dirac fermions have been identified experimentally using electron spectroscopy techniques (angle-resolved photoemission spectroscopy and scanning tunneling spectroscopy). As a consequence of their common low-energy excitations, this diverse set of materials shares a significant number of universal properties in the low-energy (infrared) limit. We review these common properties including nodal points in the excitation spectrum, density of states, specific heat, transport, thermodynamic properties, impurity resonances, and magnetic field responses, as well as discuss many-body interaction effects. We further review how the emergence of Dirac excitations is controlled by specific symmetries of the material, such as time-reversal, gauge, and spin-orbit symmetries, and how by breaking these symmetries a finite Dirac mass is generated. We give examples of how the interaction of Dirac fermions with their distinct real material background leads to rich novel physics with common fingerprints such as the suppression of back scattering and impurity-induced resonant states.
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