Electron transport in MoWSeS monolayers in the presence of an external electric field

Zibouche, Nourdine; Philipsen, Pier; Heine, Thomas; Kuc, Agnieszka

doi:10.1039/c4cp00966e

Cited by 46 publications

(46 citation statements)

References 28 publications

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“…Thus, for MoS 2 , a giant spin-orbit-induced band splitting of ∼100 meV was reported from Raman experiments [7]. In agreement, from first principles the SO splitting in T X 2 MLs was calculated to be in the range 148-480 meV, with the limiting values for MoS 2 and WTe 2 MLs, respectively [6,16]. At the same time, T X 2 monolayers are very stable with respect to external electric fields, with a semiconductor-metal transition being reported for fields stronger than 4 VÅ −1 [16].…”

Section: Introductionsupporting

confidence: 60%

Transition-metal dichalcogenide bilayers: Switching materials for spintronic and valleytronic applications

et al. 2014

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We report that an external electric field applied normal to bilayers of transition-metal dichalcogenides T X 2 (T = Mo, W, X = S, Se) creates significant spin-orbit splittings and reduces the electronic band gap linearly with the field strength. Contrary to the T X 2 monolayers, spin-orbit splittings and valley polarization are absent in bilayers due to the presence of inversion symmetry. This symmetry can be broken by an electric field, and the spin-orbit splittings in the valence band quickly reach values similar to those in the monolayers (145 meV for MoS 2 , . . . , 418 meV for WSe 2 ) at saturation fields less than 500 mVÅ −1 . The band gap closure results in a semiconductor-metal transition at field strength between 1.25 (WX 2 ) and 1.50 (MoX 2 ) VÅ −1 . Thus, by using a gate voltage, the spin polarization can be switched on and off in T X 2 bilayers, thus activating them for spintronic and valleytronic applications.

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Section: Introductionsupporting

confidence: 60%

Transition-metal dichalcogenide bilayers: Switching materials for spintronic and valleytronic applications

et al. 2014

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“…9,10 First-principles calculations on monolayers found that the band gaps are relatively stable against perpendicular electric fields, 11,12 whereas in bilayers, electric fields cause a linear reduction in the band gap. [13][14][15] In both monolayers and bilayers, bands around Γ are spin-degenerate and are susceptible to Rashba splitting under perpendicular field.…”

Section: 8mentioning

confidence: 99%

Effective tight-binding model forMX2under electric and magnetic fields

Shanavas

Satpathy

2015

Phys. Rev. B

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We present a systematic method for developing a five band Hamiltonian for the metal d orbitals that can be used to study the effect of electric and magnetic fields on multilayer MX 2 (M=Mo,W and X=S,Se) systems. On a hexagonal lattice of d orbitals, the broken inversion symmetry of the monolayers is incorporated via fictitious s orbitals at the chalcogenide sites. A tight-binding Hamiltonian is constructed and then downfolded to get effective d orbital overlap parameters using quasidegenerate perturbation theory. The steps to incorporate the effects of multiple layers, external electric and magnetic fields are also detailed. We find that an electric field produces a linear-k Rashba splitting around the Γ point, while a magnetic field removes the valley pseudospin degeneracy at the ±K points. Our model provides a simple tool to understand the recent experiments on electric and magnetic control of valley pseudospin in monolayer dichalcogendies.

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“…These giant SO splittings have been analyzed theoretically by Zhu et al 37 and range from 150 meV for MoS 2 up to 453 meV for layers that include heavier elements such as WSe 2 . 21 The appearance of SO splittings is rationalized in Figure 4. In the bulk and also in the 2H BL, inversion symmetry centers are found between the layers.…”

Section: Methodsmentioning

confidence: 92%

Transition Metal Chalcogenides: Ultrathin Inorganic Materials with Tunable Electronic Properties

2014

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CONSPECTUS: After the discovery of graphene and the development of powerful exfoliation techniques, experimental preparation of two-dimensional (2D) crystals can be expected for any layered material that is known to chemistry. Besides graphene and hexagonal boron nitride (h-BN), transition metal chalcogenides (TMC) are among the most studied ultrathin materials. In particular, single-layer MoS2, a direct band gap semiconductor with ∼1.9 eV energy gap, is popular in physics and nanoelectronics, because it nicely complements semimetallic graphene and insulating h-BN monolayer as a construction component for flexible 2D electronics and because it was already successfully applied in the laboratory as basis material for transistors and other electronic and optoelectronic devices. Two-dimensional crystals are subject to significant quantum confinement: compared with their parent layered 3D material, they show different structural, electronic, and optical properties, such as spontaneous rippling as free-standing monolayer, significant changes of the electronic band structure, giant spin-orbit splitting, and enhanced photoluminescence. Most of those properties are intrinsic for the monolayer and already absent for two-layer stacks of the same 2D crystal. For example, single-layer MoS2 is a direct band gap semiconductor with spin-orbit splitting of 150 meV in the valence band, while the bilayer of the same material is an indirect band gap semiconductor without observable spin-orbit splitting. All these properties have been observed experimentally and are in excellent agreement with calculations based on density-functional theory. This Account reports theoretical studies of a subgroup of transition metal dichalcogenides with the composition MX2, with M = Mo, or W and X = Se or S, also referred to as "MoWSeS materials". Results on the electronic structure, quantum confinement, spin-orbit coupling, spontaneous monolayer rippling, and change of electronic properties in the presence of an external electric field are reported. While all materials of the MoWSeS family share the same qualitative properties, their individual values can differ strongly, for example, the spin-orbit splitting in WSe2 reaches the value of 428 meV, nearly three times that of MoS2. Further, we discuss the effect of strain on the electronic properties (straintronics). While MoWSeS single layers are very robust against external electric fields, bilayers show a linear reduction of the band gap, even reaching a semiconductor-metal phase transition, and an increase of the spin-orbit splitting from zero to the monolayer value at rather small fields. Strain is yet another possibility to control the band gap in a linear way, and MoWSeS monolayers become metallic at strain values of ∼10%. The density-functional based tight-binding model is a useful tool to investigate the electronic and structural properties, including electron conductance, of large MoS2 structures, which show spontaneous rippling in finite-temperature molecular dynamics simulations. Structural ...

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Electron transport in MoWSeS monolayers in the presence of an external electric field

Cited by 46 publications

References 28 publications

Transition-metal dichalcogenide bilayers: Switching materials for spintronic and valleytronic applications

Transition-metal dichalcogenide bilayers: Switching materials for spintronic and valleytronic applications

Effective tight-binding model forMX2under electric and magnetic fields

Transition Metal Chalcogenides: Ultrathin Inorganic Materials with Tunable Electronic Properties

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