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6,6,12-graphyne, one of the two-dimensional carbon allotropes with the rectangular lattice structure, has two kinds of non-equivalent anisotropic Dirac cones in the first Brillouin zone. We show that Dirac cones can be tuned independently by the uniaxial compressive strain applied to graphyne, which induces n-type and p-type self-doping effect, by shifting the energy of the Dirac cones in the opposite directions. On the other hand, application of the tensile strain results into a transition from gapless to finite gap system for the monolayer. For the AB-stacked bilayer, the results predict tunability of Dirac-cones by in-plane strains as well as the strain applied perpendicular to the plane. The group velocities of the Dirac cones show enhancement in the resistance anisotropy for bilayer relative to the case of monolayer. Such tunable and direction-dependent electronic properties predicted for 6,6,12-graphyne make it to be competitive for the next-generation electronic devices at nanoscale. [ABSTRACT FROM AUTHOR]

Freestanding MoS2 nanosheets with different sizes were prepared through a simple exfoliated method by tuning the ultrasonic time in the organic solvent. Magnetic measurement results reveal the clear room-temperature ferromagnetism for all the MoS2 nanosheets, in contrast to the pristine MoS2 in its bulk form which shows diamagnetism only. Furthermore, results indicate that the saturation magnetizations of the nanosheets increase as the size decreases. Combining the X-ray photoelectron spectroscopy, transmission electron microscopy, and electron spin resonance results, it is suggested that the observed magnetization is related to the presence of edge spins on the edges of the nanosheets. These MoS2 nanosheets may find applications in nanodevices and spintronics by controlling the edge structures. [ABSTRACT FROM AUTHOR]

In this letter, we demonstrate a large enhancement of the magnetic moment in zigzag Janus MoSSe nanoribbons arising from the out-of-plane mirror symmetry breaking. Owing to the broken mirror symmetry, the orbital of the edge Mo atom is tilted and largely overlaps the orbital. As a result, a new band which is nearly completely occupied near the Fermi level emerges, leading to a large spin splitting and so a large magnetic moment in zigzag Janus MoSSe nanoribbons. The results shed new light on the understanding of magnetism correlated to the space symmetry breaking in low-dimensional materials. [ABSTRACT FROM AUTHOR]

In contrast to commonly used means such as the magnetic field, here an electric field is used to achieve a large valley splitting in the van der Waals (vdW) heterostructure WSe2/CrI3. CrI3 contributes to the spin moment. The electric field pushes the valence bands of Cr atoms close to those of the W atoms associated with pseudospin so that they can interact through the exchange interaction. The opposite helicities of pseudospin at the K and K′ points realize a valley splitting as large as 10.5 meV under an electric field of 0.1 V Å−1. The underlying physics stems from the interlayer charge transfer, where the spin conservation plays a role. [ABSTRACT FROM AUTHOR]

Creating spin current under temperature gradient in magnetic devices has resulted in a new emerging field of spin caloritronics, but extraction of material parameters i.e. Seebeck coefficient and interpretation of thermal transport characteristics are still great challenges due to the thermal contact effect, especially in a wide temperature range. Because the heat-driven voltages do not depend on the change of magnetic states in spin valve, this could be used to obtain the accurate temperature difference applied on sample and exclude the thermal contact effect. Based on this calibration, the electrical and thermal spin transport behaviors in the in-plane FeCo/Cu/FeNi spin valve were systematically studied with various temperature. We observed that the Seebeck coefficients of spin valve was negative and spin-dependent Seebeck coefficient was proportional to the asymmetry parameter in a wide temperature range from 100 to 300 K, indicating that the spin-dependent thermal transports are closely related with electrical transports in the in-plane spin valve. [ABSTRACT FROM AUTHOR]

We studied the current-induced spin–orbit torques in a perpendicularly magnetized Pt (1 nm)/Co (0.8 nm)/Pt (5 nm) heterojunction by harmonic Hall voltage measurements. Owing to similar Pt/Co/Pt interfaces, the spin–orbit torques originated from the Rashba effect are reduced, but the contribution from the spin Hall effect is still retained because of asymmetrical Pt thicknesses. When the temperature increases from 50 to 300 K, two orthogonal components of the effective field, induced by spin–orbit torques, reveal opposite temperature dependencies: the field-like term (transverse effective field) decreases from 2.3 to 2.1 (10−6 Oe (A cm−2)−1), whereas the damping-like term (longitudinal effective field) increases from 3.7 to 4.8 (10−6 Oe (A cm−2)−1). It is noticed that the damping-like term, usually smaller than the field-like term in the similar Pt/Co interfaces, is twice as large as the field-like term. As a result, the damping-like spin–orbit torque reaches an efficiency of 0.15 at 300 K. Such a temperature-dependent damping-like term in a Pt/Co/Pt heterojunction can efficiently reduce the switching current density which is 2.30  ×  106 A cm−2 at 300 K, providing an opportunity to further improve and understand spin–orbit torques induced by spin Hall effect. [ABSTRACT FROM AUTHOR]

In this letter, we demonstrate that few-layer orthorhombic arsenene is an ideal semiconductor. Owing to the layer stacking, multilayer arsenenes always behave as intrinsic direct bandgap semiconductors with gap values of approximately 1 eV. In addition, these bandgaps can be further tuned in its nanoribbons. Based on the so-called acoustic phonon limited approach, the carrier mobilities are predicted to approach as high as several thousand square centimeters per volt–second and to simultaneously exhibit high directional anisotropy. All these characteristics make few-layer arsenene promising for device applications in the semiconducting industry. [ABSTRACT FROM AUTHOR]

Using first-principles calculations we demonstrate for the first time that few-layer orthorhombic arsenic possesses a negative Poisson’s ratio. For a single layer of arsenic, the negative Poisson’s ratio is predicted to be ∼−0.09. As the number of layers increases, the magnitude of the negative Poisson’s ratio increases and finally approaches a limit at four layers, becoming very close to the bulk value of −0.13. To understand these layer-dependent negative Poisson’s ratios, we propose a rigid mechanical model in which the intra-layer bond lengths and the normal Poisson’s ratio of the in-layer plane play key roles. [ABSTRACT FROM AUTHOR]