RESUMO
Two-dimensional van der Waals magnetic atomic crystals have provided unprecedented access to magnetic ground states due to a quantum confinement effect. Here, using first-principles calculations, we demonstrate a spin-gapless molecular ferromagnet, namely, Fe2(TCNQ)2, with superior mechanical stability and a remarkable linear Dirac cone, which can be exfoliated from its already-synthesized van der Waals crystal. Especially, Young's modulus has values of 175.28 GPa·nm along the x- and y-directions with a Poisson's ratio of 0.29, while the Curie temperature within the Ising model is considerably higher than room temperature. Furthermore, spin-orbit coupling can open a band gap at the Dirac point, leading to topologically nontrivial electronic states characterized by an integer value of the Chern number and the edge states of its nanoribbon. Our results offer versatile platforms for achieving plastic spin filtering or a quantum anomalous Hall effect with promising applications in spintronics devices.
RESUMO
The weak interlayer coupling in van der Waals (vdW) magnets has confined their application to two dimensional (2D) spintronic devices. Here, we demonstrate that the interlayer coupling in a vdW magnet Fe_{3}GeTe_{2} (FGT) can be largely modulated by a protonic gate. With the increase of the protons intercalated among vdW layers, interlayer magnetic coupling increases. Because of the existence of antiferromagnetic layers in FGT nanoflakes, the increasing interlayer magnetic coupling induces exchange bias in protonated FGT nanoflakes. Most strikingly, a rarely seen zero-field cooled (ZFC) exchange bias with very large values (maximally up to 1.2 kOe) has been observed when higher positive voltages (V_{g}≥4.36 V) are applied to the protonic gate, which clearly demonstrates that a strong interlayer coupling is realized by proton intercalation. Such strong interlayer coupling will enable a wider range of applications for vdW magnets.
RESUMO
We demonstrate the direct detection of photon spin angular momentum in the mid-infrared region by a single surface-plasmon-enhanced graphene photodetector. We utilize chiral surface plasmon nanostructures as photodetector electrodes to generate photocurrents of equal and opposite sign according to incident photon spin. Our detector possesses a current circular dichroism of 60% and a responsivity of 0.80 µA/W at a resonant wavelength of 3.8 µm. The photocurrent dichroism is attributed to the presence of opposite handedness circularly polarized surface plasmon resonances on adjacent electrodes, of which each enhances graphene absorption by a factor of 17. The direct detection of spin angular momentum will be useful in the next wave of multiplexed sensing and communications systems utilizing the optical angular momentum states of light to enhance bandwidth and information collection.
