Interlayer couplings, Moiré patterns, and 2D electronic superlattices in MoS
            <sub>2</sub>
            /WSe
            <sub>2</sub>
            hetero-bilayers

Zhang, Chengfei; Chuu, Chih‐Piao; Ren, Xibiao; Li, Mingyang; Li, Lain‐Jong; Jin, Chuanhong; Chou, M. Y.; Shih, Chih‐Kang

doi:10.1126/sciadv.1601459

Cited by 463 publications

(436 citation statements)

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“…For MoS2/WSe2 heterostructures, a lateral modulation of the interlayer bandgap of up to ~15 meV was reported [50]. In particular, the difference of MoS2-CB minima at the -and K -points is sizeable modulated.…”

Section: Introductionmentioning

confidence: 95%

“…In TMD-based heterostructures, the mismatch in the lattice constants of the two constituting monolayers gives rise to a Moiré pattern, which can impact the electronic band structure [50]. For MoS2/WSe2 heterostructures, a lateral modulation of the interlayer bandgap of up to ~15 meV was reported [50].…”

Section: Introductionmentioning

confidence: 99%

“…While intralayer excitons in TMD monolayers are perfect in-plane dipoles fostering Förster-type energy transfer between hetero-bilayers [49], interlayer excitons possess a permanent out of plain component altering the coupling to light and enabling to tune the exciton properties by static electric fields perpendicular to the layers. The exciton binding energies of IXs is reduced in HS from about 0.5 eV for the individual layers to about 0.2 eV in the HS [25], but it is still one order of magnitude larger compared to IX in III-V HS.In TMD-based heterostructures, the mismatch in the lattice constants of the two constituting monolayers gives rise to a Moiré pattern, which can impact the electronic band structure [50]. For MoS2/WSe2 heterostructures, a lateral modulation of the interlayer bandgap of up to ~15 meV was reported [50].…”

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confidence: 99%

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Long-Lived Direct and Indirect Interlayer Excitons in van der Waals Heterostructures

et al. 2017

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We investigate the photoluminescence of interlayer excitons in heterostructures consisting of monolayer MoSe2 and WSe2 at low temperatures. Surprisingly, we find a doublet structure for such interlayer excitons. Both peaks exhibit long photoluminescence lifetimes of several ten nanoseconds up to 100 ns at low temperatures, which verifies the interlayer nature of both.The peak energy and linewidth of both show unusual temperature and power dependences.In particular, we observe a blue-shift of their emission energy for increasing excitation powers.At a low excitation power and low temperatures, the energetically higher peak shows several spikes. We explain the findings by two sorts of interlayer excitons; one that is indirect in real space but direct in reciprocal space, and the other one being indirect in both spaces. Our results provide fundamental insights into long-lived interlayer states in van der Waals heterostructures with possible bosonic many-body interactions.Keywords: van der Waals heterostructure, indirect excitons, interlayer exciton, photoluminescence, exciton lifetime, transition metal dichalcogenides; 2 Semiconductor heterostructures (HS) are very often the foundation for the observation of novel phenomena in both fundamental science as well as device applications. The electrical and optical properties of such HS can be engineered in a wide range resulting in precisely tailored functionalities. Of particular interest are optically active HS facilitating many device applications such as photo-detectors, solar cells, light-emitting diodes or lasers and fostering the observation of many-body driven quantum phenomena found in systems with reduced dimensionality such as quantum wells or quantum dots. Excitons are electron-hole pairs coupled by attractive Coulomb interaction which results in a ground state with a reduced energy compared to the corresponding single-particle energies. Exciton ensembles exhibit an intriguing interaction driven phase diagram with different classical and quantum phases including quantum liquids and solids [1][2][3]. The bosonic nature of excitons enables these composite particles even to condensate into macroscopic ground state wave functions forming a Bose-Einstein condensate (BEC) [4].Ensembles of indirect a.k.a. interlayer excitons (IXs) are particularly fascinating systems to explore such classical and quantum phases of interacting bosonic ensembles. IXs are composite bosons that feature enlarged lifetimes due to the reduced overlap of the electronhole wave functions resulting in dense IX ensembles that are thermalized to the lattice temperature. Besides IX ensembles in III-V HS [5][6][7][8][9][10][11][12][13][14][15], hetero-bilayers prepared from semiconducting transition metal dichalcogenides (TMDs) exhibit superior potential for studying interacting IX ensembles [3,[16][17][18][19][20][21][22][23][24][25] with intriguing spin-and valley-properties [26][27][28]. At the same time, TMDs are truly two-dimensional (2D) crystals coupled to each other or to substrat...

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Section: Introductionmentioning

confidence: 95%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

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Long-Lived Direct and Indirect Interlayer Excitons in van der Waals Heterostructures

et al. 2017

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“…However, these structures can locally exist in an incommensurate bilayer with large scale moiré superlattice pattern. 39,40,46 In a local region with a size much larger than the monolayer lattice constant but much smaller than the moiré supercell, the atomic registry between the two layers is locally indistinguishable from an R-or H-type commensurate bilayer, which is characterized by a continuously varying r 0 . The local band structure of this region is then given by that of the commensurate bilayer with the corresponding r 0 value.…”

Section: ±K-valley Coupling Strength In H-and R-type Homobilayersmentioning

confidence: 99%

Interlayer coupling in commensurate and incommensurate bilayer structures of transition-metal dichalcogenides

et al. 2017

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The interlayer couplings in commensurate and incommensurate bilayer structures of transition metal dichalcogenides are investigated with perturbative treatment. The interlayer coupling in ±K valleys can be decomposed into a series of hopping terms with distinct phase factors. In H-type and R-type commensurate bilayers, the interference between the three main hopping terms leads to a sensitive dependence of the interlayer coupling strength on the translation, that can explain the position dependent local band gap modulation in a heterobilayer moiré superlattice. The interlayer couplings in the Γ valley of valence band and Q valley of conduction band are also studied, where the strong coupling strengths of several hundred meV can play important roles in mediating the ultrafast interlayer charge transfer in heterobilayers of transition metal dichalcogenides.

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“…21,22,23 Separately, another issue that can occur in interlayer tunneling devices is the formation of moiré (interference) patterns that form between lattice-mismatched layers of 2D material. 43 These patterns can lead to shifts in the band-edge energies across the area of the tunnel junction, hence restricting the achievement of steep subthreshold slope in a device. They also can lead to noticeable changes in the interlayer separation, 44 which in turn affects the tunnel current, as a function of position throughout the moiré unit cell.…”

Section: Resultsmentioning

confidence: 99%

Magnitude of the current in 2D interlayer tunneling devices

Feenstra

Barrera

et al. 2018

J. Phys.: Condens. Matter

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Abstract:Using the Bardeen tunneling method with first-principles wave functions, computations are made of the tunneling current in graphene / hexagonal-boron-nitride / graphene (G/h-BN/G) vertical structures. Detailed comparison with prior experimental results is made, focusing on the magnitude of the achievable tunnel current. With inclusion of the effects of translational and rotational misalignment of the graphene and the h-BN, predicted currents are found to be about 15 larger than experimental values. A reduction in this discrepancy, to a factor of 2.5, is achieved by utilizing a realistic size for the band gap of the h-BN, hence affecting the exponential decay constant for the tunneling.

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Interlayer couplings, Moiré patterns, and 2D electronic superlattices in MoS ₂ /WSe ₂ hetero-bilayers

Abstract: A periodic modulation of the local bandgap in the rotationally aligned MoS2/WSe2 bilayer creates a 2D electronic superlattice.

Cited by 463 publications

References 44 publications

Long-Lived Direct and Indirect Interlayer Excitons in van der Waals Heterostructures

Long-Lived Direct and Indirect Interlayer Excitons in van der Waals Heterostructures

Interlayer coupling in commensurate and incommensurate bilayer structures of transition-metal dichalcogenides

Magnitude of the current in 2D interlayer tunneling devices

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Interlayer couplings, Moiré patterns, and 2D electronic superlattices in MoS 2 /WSe 2 hetero-bilayers

Abstract: A periodic modulation of the local bandgap in the rotationally aligned MoS2/WSe2 bilayer creates a 2D electronic superlattice.

Cited by 463 publications

References 44 publications

Long-Lived Direct and Indirect Interlayer Excitons in van der Waals Heterostructures

Long-Lived Direct and Indirect Interlayer Excitons in van der Waals Heterostructures

Interlayer coupling in commensurate and incommensurate bilayer structures of transition-metal dichalcogenides

Magnitude of the current in 2D interlayer tunneling devices

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Interlayer couplings, Moiré patterns, and 2D electronic superlattices in MoS ₂ /WSe ₂ hetero-bilayers