Stacking Domains and Dislocation Networks in Marginally Twisted Bilayers of Transition Metal Dichalcogenides

Enaldiev, V. V.; Zólyomi, Viktor; Yelgel, Celal; Magorrian, Samuel; Fal’ko, Vladimir I.

doi:10.1103/physrevlett.124.206101

Cited by 139 publications

(274 citation statements)

References 72 publications

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“…II for further discussion [43]). In particular, the extracted dipole moment is in excellent agreement with recent DFT calculations for 0°twisted bilayer WSe 2 [46], where the wave function at the Q point was predicted to have a 62%-38% distribution between the two layers (see Supplemental Sec. V [43] for further discussion).…”

supporting

confidence: 86%

Electrically Tunable Valley Dynamics in Twisted WSe2/WSe2 Bilayers

et al. 2020

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The twist degree of freedom provides a powerful new tool for engineering the electrical and optical properties of van der Waals heterostructures. Here, we show that the twist angle can be used to control the spin-valley properties of transition metal dichalcogenide bilayers by changing the momentum alignment of the valleys in the two layers. Specifically, we observe that the interlayer excitons in twisted WSe 2 =WSe 2 bilayers exhibit a high (>60%) degree of circular polarization (DOCP) and long valley lifetimes (>40 ns) at zero electric and magnetic fields. The valley lifetime can be tuned by more than 3 orders of magnitude via electrostatic doping, enabling switching of the DOCP from ∼80% in the n-doped regime to <5% in the p-doped regime. These results open up new avenues for tunable chiral light-matter interactions, enabling novel device schemes that exploit the valley degree of freedom.

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confidence: 86%

Electrically Tunable Valley Dynamics in Twisted WSe2/WSe2 Bilayers

et al. 2020

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“…The MoSe 2 crystal with a native bilayer region in 2H or AA′ stacking was twisted away from parallel R-type alignment by about 4 ∘ with respect to the WSe 2 monolayer. At such relatively large angles, we expect the moiré heterostructure to be robust against reconstruction [39][40][41] and thus to contrast previous studies of MoSe 2 -WSe 2 HBLs carefully aligned for zero twist angle in Rtype stacking 24,28 as well as moiré-free HBLs obtained from chemical vapor deposition with lattice-mismatch relaxation and inherent alignment 21,23 .…”

Section: Resultsmentioning

confidence: 73%

“…This implies that AA domains dominate the HBL PL in rigid moiré supercells, although A′B′ regions should be at least of comparable size 39 . In the presence of reconstruction, one would expect predominance of energetically favored A′B′ and AB′ triangular domains of comparable area 39,40,50 . Without reconstruction, on the other hand, a reversal in the energetic ordering of AA and A′B′ interlayer excitons at finite twist angles, as predicted recently by theory for R-type MoSe 2 -WSe 2 heterostructures 51 , would satisfactorily explain the observation.…”

Section: Resultsmentioning

confidence: 99%

Moiré excitons in MoSe2-WSe2 heterobilayers and heterotrilayers

et al. 2021

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Layered two-dimensional materials exhibit rich transport and optical phenomena in twisted or lattice-incommensurate heterostructures with spatial variations of interlayer hybridization arising from moiré interference effects. Here, we report experimental and theoretical studies of excitons in twisted heterobilayers and heterotrilayers of transition metal dichalcogenides. Using MoSe2-WSe2 stacks as representative realizations of twisted van der Waals bilayer and trilayer heterostructures, we observe contrasting optical signatures and interpret them in the theoretical framework of interlayer moiré excitons in different spin and valley configurations. We conclude that the photoluminescence of MoSe2-WSe2 heterobilayer is consistent with joint contributions from radiatively decaying valley-direct interlayer excitons and phonon-assisted emission from momentum-indirect reservoirs that reside in spatially distinct regions of moiré supercells, whereas the heterotrilayer emission is entirely due to momentum-dark interlayer excitons of hybrid-layer valleys. Our results highlight the profound role of interlayer hybridization for transition metal dichalcogenide heterostacks and other realizations of multi-layered semiconductor van der Waals heterostructures.

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“…The domain formation was theoretically predicted for the first time in Ref. 27 via conformational considerations, and indeed, density functional theory calculations confirmed that in the above cases, the two stacking configurations are the energetically favorable lattice arrangements 24,25,28,29 (also see Ref. 30 for a classical modeling).…”

mentioning

confidence: 67%

Low-frequency Raman scattering in WSe2−MoSe2 heterobilayers: Evidence for atomic reconstruction

Höller

Meier

Kempf

et al. 2020

Applied Physics Letters

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We investigate WSe 2 -MoSe 2 heterobilayers with different twist angles h 6 d between the two layers by low-frequency Raman scattering. In sufficiently aligned samples with h ¼ 0 or h ¼ 60 and d Շ 3 , we observe an interlayer shear mode (ISM), which is a clear sign of a commensurate bilayer structure, i.e., the layers must undergo an atomic reconstruction to form R-type or H-type stacking orders. We find slightly different ISM energies of about 18 cm -1 and 17 cm -1 for H-type and R-type reconstructions, respectively, independent of the exact value of h 6 d. Our findings are corroborated by the fact that the ISM is not observed in samples with twist angles, which deviate by d > 3 from 0 or 60 . This is expected since, in such incommensurate structures, with the possibility of Moir e-lattice formation, there is no restoring force for an ISM. Furthermore, we observe the ISM even in sufficiently aligned heterobilayers, which are encapsulated in hexagonal Boron nitride. This is particularly relevant for the characterization of high-quality heterostructure devices.

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Stacking Domains and Dislocation Networks in Marginally Twisted Bilayers of Transition Metal Dichalcogenides

Cited by 139 publications

References 72 publications

Electrically Tunable Valley Dynamics in Twisted WSe2/WSe2 Bilayers

Electrically Tunable Valley Dynamics in Twisted WSe2/WSe2 Bilayers

Moiré excitons in MoSe2-WSe2 heterobilayers and heterotrilayers

Low-frequency Raman scattering in WSe2−MoSe2 heterobilayers: Evidence for atomic reconstruction

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