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

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

doi:10.1103/physrevb.90.125440

Cited by 122 publications

(123 citation statements)

References 38 publications

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“…14, 15 The Rashba parameter, α R values for the d z 2 bands estimated from the DFT calculations are plotted in Fig. 4(b).…”

Section: A Density Functional Resultsmentioning

confidence: 99%

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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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“…14, 15 The Rashba parameter, α R values for the d z 2 bands estimated from the DFT calculations are plotted in Fig. 4(b).…”

Section: A Density Functional Resultsmentioning

confidence: 99%

“…[13][14][15] In both monolayers and bilayers, bands around Γ are spin-degenerate and are susceptible to Rashba splitting under perpendicular field. Supercell calculations of MX 2 on Bi(111) heterostructures show giant Rashba splitting of the bands near Γ.…”

Section: 8mentioning

confidence: 99%

Effective tight-binding model forMX2under electric and magnetic fields

Shanavas

Satpathy

2015

Phys. Rev. B

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“…9,10 For multilayers, two single-layers are stacked as a unit bilayer by weak van-der-Waals forces, recovering inversion symmetry (centred at small black circles in The band structure of multilayer 2H-TMDs is highly susceptible to various physical parameters, such as thickness, 13 stacking, 14 strain, 15,16 and electric field. 17,18 Although the structural variation of thickness and stacking modulates the magnitude of the bandgap, there is little change in the local gap at the K point, 8 which is critical for optical properties of 2H-TMDs. 19,20 On the other hand, the application of external electric field vertically to TMD layers, which is more viable in gated devices, is widely predicted to modulate the local bandgap at the K point.…”

Section: Abstract: Bandgap Engineering Two-dimensional Semiconductormentioning

confidence: 99%

Universal Mechanism of Band-Gap Engineering in Transition-Metal Dichalcogenides

et al. 2017

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van der Waals two-dimensional (2D) semiconductors have emerged as a class of materials with promising device characteristics owing to the intrinsic band gap. For realistic applications, the ideal is to modify the band gap in a controlled manner by a mechanism that can be generally applied to this class of materials. Here, we report the observation of a universally tunable band gap in the family of bulk 2H transition metal dichalcogenides (TMDs) by in situ surface doping of Rb atoms. A series of angle-resolved photoemission spectra unexceptionally shows that the band gap of TMDs at the zone corners is modulated in the range of 0.8–2.0 eV, which covers a wide spectral range from visible to near-infrared, with a tendency from indirect to direct band gap. A key clue to understanding the mechanism of this band-gap engineering is provided by the spectroscopic signature of symmetry breaking and resultant spin-splitting, which can be explained by the formation of 2D electric dipole layers within the surface bilayer of TMDs. Our results establish the surface Stark effect as a universal mechanism of band-gap engineering on the basis of the strong 2D nature of van der Waals semiconductors.

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“…As a semiconducting alternative to graphene, TMDs have promising applications in photonics [1,2], optoelectronics [3,4], valleytronics [5], field effect transistors [6], gas sensors [7], mechanical resonators [8,9] and energy storage devices [10].…”

Section: Introductionmentioning

confidence: 99%

Influence of the substrate material on the optical properties of tungsten diselenide monolayers

et al. 2017

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Monolayers of transition-metal dichalcogenides such as WSe 2 have become increasingly attractive due to their potential in electrical and optical applications. Because the properties of these 2D systems are known to be affected by their surroundings, we report how the choice of the substrate material affects the optical properties of monolayer WSe 2 . To accomplish this study, pump-density-dependent micro-photoluminescence measurements are performed with time-integrating and time-resolving acquisition techniques. Spectral information and power-dependent mode intensities are compared at 290K and 10K for exfoliated WSe 2 on SiO 2 /Si, sapphire (Al 2 O 3 ), hBN/Si 3 N 4 /Si, and MgF 2 , indicating substrate-dependent appearance and strength of exciton, trion, and biexciton modes. Additionally, one CVD-grown WSe 2 monolayer on sapphire is included in this study for direct comparison with its exfoliated counterpart. Time-resolved micro-photoluminescence shows how radiative decay times strongly differ for different substrate materials. Our data indicates exciton-exciton annihilation as a shortening mechanism at room temperature, and subtle trends in the decay rates in correlation to the dielectric environment at cryogenic temperatures. On the measureable time scales, trends are also related to the extent of the respective 2D-excitonic modes' appearance. This result highlights the importance of further detailed characterization of exciton features in 2D materials, particularly with respect to the choice of substrate.

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

Cited by 122 publications

References 38 publications

Effective tight-binding model forMX2under electric and magnetic fields

Effective tight-binding model forMX2under electric and magnetic fields

Universal Mechanism of Band-Gap Engineering in Transition-Metal Dichalcogenides

Influence of the substrate material on the optical properties of tungsten diselenide monolayers

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