Giant tunable Rashba spin splitting in two-dimensional polar perovskites TlSnX3 (X = Cl, Br, I).

The electronic structures and Rashba effect of two-dimensional polar tetragonal perovskites TlSnX3 (X = Cl, Br, I) are investigated by first-principles density functional theory, and intrinsic Rashba effects are found around the Γ point. In particular, TlSnI3 has the largest Rashba constant of 1.072 eV Å-1. Additionally, TlSnBr3 and TlSnI3 respond strongly to the applied electric field, and the electric field responsivity of TlSnI3 can reach 0.790 e Å2. Therefore, due to the large Rashba constants and strong electric field responses, these 2D polar perovskites are promising semiconductor materials with short channel lengths. The nano-scale short spin coherence length can keep the spin coherence of spin FETs, which is superior to the traditional 3D micron spin FETs, and will show a broad application prospect in the Rashba semiconductor field.

Coexisting unconventional Rashba- and Zeeman-type spin splitting in Pb-adsorbed monolayer WSe2.

Based on first-principles calculations, the unconventional Rashba- and Zeeman-type spin splitting can simultaneously coexist in the Pb-adsorbed monolayer WSe2system. The first two adsorption configurationst1andt2show remarkable features under the spin-orbit coupling, in which two split energy branches show same spin states at the left or right side of Γ, and the spin polarization is reversed for both Rashba band branches. For the second adsorption configuration, an energy gap was observed near the unconventional spin polarization caused by the repelled Rashba bands for avoid crossing, and this gap can produce non-dissipative spin current by applying the voltage. The results fort2configuration with spin reversal show that the repel band gap and Rashba parameter can be effectively regulated within the biaxial strain range of -8% to 6%. By changing the adsorption distancedbetween Pb and the neighboring Se atom layer, the reduceddcaused the transfer from Rashba-type to Zeeman-type spin splitting. This predicted adsorption system would be promising for spintronic applications.

Large Rashba splitting, carrier mobility, and valley polarization in a 1T-SnS2/MoTe2 heterostructure.

The structural and electronic properties of the 1T-SnS2/MoTe2 heterostructure were investigated based on density functional theory and Berry curvature calculations. Considering the strong spin-orbit coupling and space inversion asymmetry, large Rashba spin splitting of electronic bands appeared in this hybrid system. The Rashba coupling parameter αR in 1T-SnS2/MoTe2 reached 0.383 eV Å. Importantly, αR can be effectively tuned by biaxial strain. Moreover, our first-principles calculations show that the 1T-SnS2/MoTe2 heterostructure possesses a high carrier mobility of 5038.46 cm2 V-1 s-1. The Berry curvature and spin splitting were opposite at the K and K' valleys. Hence, the valleys and spins were simultaneously locked and polarized, and the valley and spin Hall effects simultaneously occurred.

Biaxial strain effect on the electronic structure and valleytronic properties of a MoS2/CoO(111) heterostructure.

The biaxial strain effect on the electronic structure and valleytronic properties, such as valley splitting and Berry curvature, of monolayer MoS2 induced by the magnetic proximity effect of an antiferromagnetic CoO(111) substrate is investigated by density functional theory. The biaxial tensile strain could continually tune the magnitude of spin and valley splitting of the MoS2/CoO(111) heterostructure, because the spin splitting at the K and K' valleys decreases, whereas the valley splitting increases slightly in the tensile strain range of 0-6%. The ferromagnetic order of MoS2 in the heterostructure induced by the magnetic CoO substrate is retained under a biaxial tensile strain of 2% to 6% compared with the unstrained case. In particular, the intensity of the exchange field due to the magnetic proximity effect of CoO weakens monotonously with biaxial tensile strain increasing from 0% to 6%, thereby also leading to a monotonous reduction of the Berry curvature. The regulation of valley splitting and Berry curvature by biaxial tensile strain will provide the MoS2/CoO(111) heterostructure with high potential in future valleytronic applications.

Realization of a half-metallic state on bilayer WSe2 using doping transition metals (Cr, Mn, Fe, Co, Ni) in its interlayer.

The structural, electronic and magnetic properties of Cr, Mn, Fe, Co and Ni-doped bilayer WSe2 are predicted by using first principles calculations. The doped transition-metal (TM) atoms show a covalent-binding with the nearest Se atoms. The calculated electronic structures reveal that the TM Cr, Mn, Fe and Co-doped bilayer WSe2 exhibits a half-metallic character with a 100% spin polarization at the Fermi level, and the reason is ascribed to the strong hybridization peak between the transition metals and the parent W and Se atoms. The Ni-doped bilayer WSe2 is still a semiconductor with nonmagnetism. The Fe-doped system has a robust stability of half-metallicity because there are three connected states peak spanning the Fermi level. The doping of Cr, Mn, Fe and Co atoms leads to a prominent total magnetism (0.93-3.65 [Formula: see text] moment per unit cell), and an induced ∼0.3 [Formula: see text] moment in parent W atoms is found in addition to the main contribution of TM atomic magnetism (0.71-3.33 [Formula: see text] moment per atom). The predicted Cr, Mn, Fe and Co-doped bilayer WSe2 should be the candidate materials for spintronic devices due to their magnetic and half-metallic nature.