Quantifying van der Waals Interactions in Layered Transition Metal Dichalcogenides from Pressure-Enhanced Valence Band Splitting

Ci, Penghong; Chen, Yabin; Kang, Jun; Suzuki, Ryuji; Choe, Hwan Sung; Suh, Joonki; Ko, Changhyun; Park, Taegyun; Shi, Ke; Iwasa, Yoshihiro; Tongay, Sefaattin; Ager, Joel W.; Wang, Lin Wang; Wu, Junqiao

doi:10.1021/acs.nanolett.7b02159

Cited by 60 publications

(56 citation statements)

References 35 publications

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“…This is understandable because, as shown in the partial density of states plot in Fig. 2d , the V S state originates mostly from the 4d (5d) orbitals of the Mo (W) atoms, rather than the S atoms, sharing the same orbital composition as the CBM 31 , 32 . Following this finding, anion impurities (such as oxygen) substituting S are predicted to create deep levels also about 0.3 eV below the CBM of the host (see Supplementary Fig.…”

Section: Resultsmentioning

confidence: 87%

Chemical trends of deep levels in van der Waals semiconductors

Tian

Kang

et al. 2020

Nat Commun

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Properties of semiconductors are largely defined by crystal imperfections including native defects. Van der Waals (vdW) semiconductors, a newly emerged class of materials, are no exception: defects exist even in the purest materials and strongly affect their electrical, optical, magnetic, catalytic and sensing properties. However, unlike conventional semiconductors where energy levels of defects are well documented, they are experimentally unknown in even the best studied vdW semiconductors, impeding the understanding and utilization of these materials. Here, we directly evaluate deep levels and their chemical trends in the bandgap of MoS2, WS2 and their alloys by transient spectroscopic study. One of the deep levels is found to follow the conduction band minimum of each host, attributed to the native sulfur vacancy. A switchable, DX center - like deep level has also been identified, whose energy lines up instead on a fixed level across different hosts, explaining a persistent photoconductivity above 400 K.

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Section: Resultsmentioning

confidence: 87%

Chemical trends of deep levels in van der Waals semiconductors

Tian

Kang

et al. 2020

Nat Commun

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“…Hydrostatic pressure can be used to continuously control the interlayer coupling via the interlayer spacing in vdW crystals. This has recently been shown to modify the bands in graphene/hBN moiré superlattices 21 and transition metal dichalcogenides 22,23 , as well as correlated electronic phases in twisted bilayer graphene 3 . Pressure has also been applied to a number of bulk vdW magnets, successfully altering the critical temperature [24][25][26][27] .…”

Section: Maintextmentioning

confidence: 99%

Switching 2D magnetic states via pressure tuning of layer stacking

et al. 2019

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The physical properties of two-dimensional van der Waals (2D vdW) crystals depend sensitively on the interlayer coupling, which is intimately connected to the stacking arrangement and the interlayer spacing. For example, simply changing the twist angle between graphene layers can induce a variety of correlated electronic phases 1-8 , which can be controlled further in a continuous manner by applying hydrostatic pressure to decrease the interlayer spacing 3 . In the recently discovered 2D magnets 9,10 , theory suggests that the interlayer exchange coupling strongly depends on layer separation, while the stacking arrangement can even change the sign of the magnetic exchange, thus drastically modifying the ground state 11-15 . Here, we demonstrate pressure tuning of magnetic order in the 2D magnet CrI3. We probe the magnetic states using tunneling 16,17 and scanning magnetic circular dichroism microscopy measurements 10 . We find that the interlayer magnetic coupling can be more than doubled by hydrostatic pressure. In bilayer CrI3, pressure induces a transition from layered antiferromagnetic to ferromagnetic phases. In trilayer CrI3, pressure can create coexisting domains of three phases, one ferromagnetic and two distinct antiferromagnetic. The observed changes in magnetic order can be explained by changes in the stacking arrangement. Such coupling between stacking order and magnetism provides ample opportunities for designer magnetic phases and functionalities. discussion.

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“…We emphasize that the Se-p z effect appears observable only when the VB valley splitting (W-Cr coupling) is weak. Recently, researchers have begun to realize the complexity of the interlayer coupling arising from the p z orbital in TMDs [48][49][50] Interestingly, in bilayer MoS 2 , a pressure induced increase of the interaction between the S-p z orbitals is observed to lead to a considerable spin splitting without considering the SOC effect 49 .…”

Section: The Valence (∆Vb) and Conduction Band Valley Splitting (∆Cb)mentioning

confidence: 99%

Valley splitting in the van der Waals heterostructure WSe2/CrI3 : The role of atom superposition

et al. 2019

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Recent experiment shows that the K ′ K valley degeneracy can be lifted in a monolayer WSe2 deposited on a layered ferromagnetic substrate of CrI3. In this work, we take a van der Waals heterostructure WSe2/CrI3 to model the monolayer WSe2 on the CrI3 substrate and investigate the effects underpinning the K ′ K valley splitting based on first-principles calculations. We demonstrate that the interfacial atom superposition plays an important role and a W-Cr superposition is essential for a relatively large valley splitting. The results indicate inevitable sample-to-sample variations in the K ′ K valley splitting in the WSe2/CrI3. Furthermore, we show that the K ′ K valley splitting can be tuned in a trilayer CrI3/WSe2/CrI3 from nearly zero to more than two times of that in the bilayer WSe2/CrI3 by manipulating the layer alignment.

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Quantifying van der Waals Interactions in Layered Transition Metal Dichalcogenides from Pressure-Enhanced Valence Band Splitting

Cited by 60 publications

References 35 publications

Chemical trends of deep levels in van der Waals semiconductors

Chemical trends of deep levels in van der Waals semiconductors

Switching 2D magnetic states via pressure tuning of layer stacking

Valley splitting in the van der Waals heterostructure WSe2/CrI3 : The role of atom superposition

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