Symmetries and hybridization in the indirect interaction between magnetic moments inMoS2nanoflakes (original) (raw)
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N ov 2 01 6 Non-colinear exchange interaction in transition metal dichalcogenide edges
2018
We study the Ruderman-Kittel-Kasuya-Yosida effective exchange interaction between magnetic impurities embedded on the edges of transition-metal dichalcogenide flakes, using a three-orbital tight-binding model. Electronic states lying midgap of the bulk structure have strong onedimensional (1D) character, localized on the edges of the crystallite. This results in exchange interactions with 1/r (or slower) decay with distance r, similar to other 1D systems. Most interestingly, however, the strong spin-orbit interaction in these materials results in sizable non-collinear Dzyaloshinskii-Moriya interactions between impurities, comparable in size to the usual Ising and in-plane components. Varying the relevant Fermi energy by doping or gating may allow one to modulate the effective interactions, controlling the possible helical ground state configurations of multiple impurities.
Noncollinear exchange interaction in transition metal dichalcogenide edges
Physical Review B, 2016
We study the Ruderman-Kittel-Kasuya-Yosida effective exchange interaction between magnetic impurities embedded on the edges of transition-metal dichalcogenide flakes, using a three-orbital tight-binding model. Electronic states lying midgap of the bulk structure have strong onedimensional (1D) character, localized on the edges of the crystallite. This results in exchange interactions with 1/r (or slower) decay with distance r, similar to other 1D systems. Most interestingly, however, the strong spin-orbit interaction in these materials results in sizable non-collinear Dzyaloshinskii-Moriya interactions between impurities, comparable in size to the usual Ising and in-plane components. Varying the relevant Fermi energy by doping or gating may allow one to modulate the effective interactions, controlling the possible helical ground state configurations of multiple impurities.
Spin response and collective modes in simple metal dichalcogenides
Physical Review B
Transition metal dichalcogenide (TMD) monolayers are interesting materials in part because of their strong spin-orbit coupling. This leads to intrinsic spin-splitting of opposite signs in opposite valleys, so the valleys are intrinsically spin-polarized when hole-doped. We study spin response in a simple model of these materials, with an eye to identifying sharp collective modes (i.e, spin-waves) that are more commonly characteristic of ferromagnets. We demonstrate that such modes exist for arbitrarily weak repulsive interactions, even when they are too weak to induce spontaneous ferromagnetism. The behavior of the spin response is explored for a range of hole dopings and interaction strengths.
Valley-polarized magnetic state in hole-doped monolayers of transition-metal dichalcogenides
Physical Review B
We compute the valley/magnetic phase diagram of monolayers of transition-metal dichalcogenides in the hole-doped region where spin-orbit effects are particularly relevant. Taking into account the moderate to high local electron-electron interactions due to the presence of transition-metal atoms, we show that the system is unstable to an itinerant ferromagnetic phase where all charge carriers are spin and valley polarized. This phase shows an anomalous charge Hall and anomalous spin Hall response, and may thus be detected experimentally.
npj 2D Materials and Applications
Using first-principles calculations, we investigate the magnetic order in two-dimensional (2D) transition-metal-dichalcogenide (TMD) monolayers: MoS2, MoSe2, MoTe2, WSe2, and WS2 substitutionally doped with period four transition-metals (Ti, V, Cr, Mn, Fe, Co, Ni). We uncover five distinct magnetically ordered states among the 35 distinct TMD-dopant pairs: the non-magnetic (NM), the ferromagnetic with out-of-plane spin polarization (Z FM), the out-of-plane polarized clustered FMs (clustered Z FM), the in-plane polarized FMs (X–Y FM), and the anti-ferromagnetic (AFM) state. Ni and Ti dopants result in an NM state for all considered TMDs, while Cr dopants result in an anti-ferromagnetically ordered state for all the TMDs. Most remarkably, we find that Fe, Mn, Co, and V result in an FM ordered state for all the TMDs, except for MoTe2. Finally, we show that V-doped MoSe2 and WSe2, and Mn-doped MoS2, are the most suitable candidates for realizing a room-temperature FM at a 16–18% atomic ...
Proximity-induced spin-polarized magnetocaloric effect in transition metal dichalcogenides
Physical Review B, 2022
We explore proximity-induced magnetocaloric effect (MCE) on transition metal dichalcogenides, focusing on a two-dimensional (2D) MoTe2 monolayer deposited on a ferromagnetic semiconductor EuO substrate connected to a heat source. We model this heterostructure using a tight-binding model, incorporating exchange and Rashba fields induced by proximity to EuO, and including temperature through Fermi statistics. The MCE is induced on the 2D MoTe2 layer due to the EuO substrate, revealing large spin-polarized entropy changes for energies out of the band gap of the MoTe2-EuO system. By gating the chemical potential, the MCE can be tuned to produce heating for spin up and cooling for spin down across the K and K valley splitting in the valence band, whereas either heats or cools for both spins in the conduction band. The Rashba field enhances the MCE in the valence zone while decreasing it in the conduction bands. The exchange field-induced MCE could be useful to produce tunable spin-polarized thermal responses in magnetic proximitized 2D materials.
Giant valley-Zeeman coupling in the surface layer of an intercalated transition metal dichalcogenide
Nature Materials
Spin-valley locking is ubiquitous to transition-metal dichalcogenides (TMDs) with local or global inversion asymmetry, in turn stabilising properties such as Ising superconductivity, and opening routes towards 'valleytronics'. The underlying valley spin splitting is set by spin-orbit coupling, but can be tuned via application of external magnetic fields or through proximity coupling. However, only modest changes have been realised to date. Here, we investigate the electronic structure of the V-intercalated TMD V 1/3 NbS2 using microscopic area spatially-and angle-resolved photoemission spectroscopy. Our measurements and corresponding density-functional theory calculations reveal that the bulk magnetic order induces a giant valley-selective Ising coupling exceeding 50 meV in the surface NbS2 layer, equivalent to application of a ∼ 250 T magnetic field. This is of comparable magnitude to the intrinsic spin-orbit splittings, and indicates how coupling of local magnetic moments to itinerant states of a TMD monolayer provides a powerful route to controlling their valley spin splittings.
RKKY interaction and intervalley processes in p-doped transition metal dichalcogenides
We study the Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction in p-doped transition metal dichalcogenides such as MoS2 and WS2. We consider magnetic impurities hybridized to the Mo d-orbitals characteristic of the valence bands. Using the Matsubara Green’s function formalism, we obtain the two-impurity interaction vs their separation and chemical potential of the system, accounting for the important angular dependence which reflects the underlying triangular lattice symmetry. The inclusion of the valence band valley at the \Gamma point results in a strong enhancement of the interaction. Electron scattering processes transferring momentum between valleys at different symmetry points give rise to complex spatial oscillation patterns. Variable doping would allow the exploration of rather interesting behavior in the interaction of magnetic impurities on the surfaces of these materials, including the control of the interaction symmetry, which can be directly probed in STM experiments.
Journal of Applied Physics, 2017
The established spin splitting in monolayer (ML) of transition metal dichalcogenides (TMDs) that is caused by inversion symmetry breaking is dictated by mirror symmetry operations to exhibit fully out-of-plane direction of spin polarization. Through first-principles density functional theory calculations, we show that polarity-induced mirror symmetry breaking leads to sizable spin splitting having in-plane spin polarization. These splittings are effectively controlled by tuning the polarity using biaxial strain. Furthermore, the admixtures of the out-of-plane and in-plane spin-polarized states in the strained polar systems are identified, which is expected to influence the spin relaxation through the Dyakonov-Perel mechanism. Our study clarified that the polarity-induced mirror symmetry breaking plays an important role in controlling the spin splitting and spin relaxation in the TMDs ML, which is useful for designing future spintronic devices.
Nature Communications, 2021
Dzyaloshinskii–Moriya interaction (DMI) is vital to form various chiral spin textures, novel behaviors of magnons and permits their potential applications in energy-efficient spintronic devices. Here, we realize a sizable bulk DMI in a transition metal dichalcogenide (TMD) 2H-TaS2 by intercalating Fe atoms, which form the chiral supercells with broken spatial inversion symmetry and also act as the source of magnetic orderings. Using a newly developed protonic gate technology, gate-controlled protons intercalation could further change the carrier density and intensely tune DMI via the Ruderman–Kittel–Kasuya–Yosida mechanism. The resultant giant topological Hall resistivity {\rho }_{{xy}}^{T}ρxyTofρ x y T ofρxyTof1.41{\mathrm{\mu}} \Omega \cdot {{\mathrm{cm}}}1.41μΩ⋅cmat1.41 μ Ω ⋅ cm at1.41μΩ⋅cmat{V}_{g}=-5.2{\mathrm{V}}Vg=−5.2V(aboutV g = − 5.2 V (aboutVg=−5.2V(about424 \%$$ 424 % larger than the zero-bias value) is larger than most known chiral magnets. Theoretical analysis indicates that such a large topological Hall effec...