Electronic Structure of Epitaxial Single-Layer<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow><mml:mi>MoS</mml:mi></mml:mrow><mml:mn>2</mml:mn></mml:msub></mml:math>

Miwa, Jill A.; Ulstrup, Søren; Sørensen, Signe G.; Dendzik, Maciej; Čabo, Antonija Grubišić; Bianchi, Marco; Lauritsen, Jeppe V.; Hofmann, Philip

doi:10.1103/physrevlett.114.046802

Cited by 162 publications

(227 citation statements)

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“…Specifically, the observation that VB A renormalization coincides with occupation of the CBM suggests that the renormalization is caused by new scattering channels available upon occupation of the conduction band. Previous works using surface potassium deposition for electron-doping of single-layer TMDs on conductive substrates [16][17][18] , where the Coulomb interactions are already strongly screened in the undoped case 9 , have shown no such changes in Δ SO . We believe that the reduced dielectric constant of the h-BN substrate plays a key role for these observations as it leads to reduced screening of the many-body interactions in the bare single-layer WS 2 .…”

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confidence: 99%

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Giant spin-splitting and gap renormalization driven by trions in single-layer WS2/h-BN heterostructures

et al. 2018

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In two-dimensional (2D) semiconducting transition metal dichalcogenides (TMDs), new electronic phenomena such as tunable bandgaps 1-3 and strongly bound excitons and trions emerge from strong many-body effects [4][5][6] , beyond the spin and valley degrees of freedom induced by spin-orbit coupling and by lattice symmetry 7 . Combining single-layer TMDs with other 2D materials in van der Waals heterostructures offers an intriguing means of controlling the electronic properties through these many-body effects, by means of engineered interlayer interactions [8][9][10] . Here, we use micro-focused angle-resolved photoemission spectroscopy (microARPES) and in situ surface doping to manipulate the electronic structure of single-layer WS 2 on hexagonal boron nitride (WS 2 /h-BN). Upon electron doping, we observe an unexpected giant renormalization of the spin-orbit splitting of the single-layer WS 2 valence band, from 430 meV to 660 meV, together with a bandgap reduction of at least 325 meV, attributed to the formation of trionic quasiparticles. These findings suggest that the electronic, spintronic and excitonic properties are widely tunable in 2D TMD/h-BN heterostructures, as these are intimately linked to the quasiparticle dynamics of the materials [11][12][13] . Coulomb interactions in 2D materials are several times stronger than in their 3D counterparts. In 2D TMDs, this is most directly evidenced by the presence of excitons with binding energies an order of magnitude higher than in the bulk 4 . Although the excitons in these 2D materials have been widely studied by optical techniques 13 , the impact of strong electron-electron interactions on the quasiparticle band structure remains unclear. Theory predicts that many-body effects will influence the spin-orbit splitting around the valenceband maximum (VBM) and conduction-band minimum (CBM) 14 . Although these should be observable by ARPES, a direct probe of many-body effects 15 , measurements so far have mainly focused on the layer-dependence of the single-particle spectrum and the direct bandgap transition in 2D TMD systems, including epitaxial single- . Unfortunately, the lateral size of mechanically assembled heterostructures is usually of the order of 10 μ m, much smaller than the beam spot of typical ARPES setups (≳ 100 μ m). Furthermore, sample charging on insulating bulk h-BN substrates would complicate ARPES experiments.We overcome these challenges as follows. We realize a high-quality 2D semiconductor-insulator interface by mechanically transferring a relatively large (~100 μ m) single-layer WS 2 crystal onto a thin flake of h-BN that has itself been transferred onto a degenerately doped TiO 2 substrate, as depicted in Fig. 1a. Sample charging is avoided because there is electrical contact from the continuous single-layer WS 2 flake to both the h-BN and the conductive TiO 2 . Figure 1b is an optical microscope image of the sample, including a flake of h-BN, approximately 100 μ m wide, surrounded by several transferred flakes of single-layer WS 2 on the Ti...

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“…16 ) and single-layer WSe 2 (ref. 17 ) grown on doped multilayer graphene, and single-layer MoS 2 grown on a metal surface 18 . On such conductive substrates, the interfacial interactions and screening are known to strongly influence the electronic properties of the single-layer TMD 9 .…”

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Giant spin-splitting and gap renormalization driven by trions in single-layer WS2/h-BN heterostructures

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“…There have been a number of ARPES studies either on bulk MX 2 samples [26,27,28] or a few layer samples [20,21,29,30] prepared by various methods such as exfoliation, chemical vapor deposition (CVD), and epitaxial growth. They all observe sizable splitting in VB at the K-point, with size ∼ 170 meV for MoS 2 and MoSe 2 and ∼ 450 meV for WS 2 and WSe 2 as W induces larger SOC.…”

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confidence: 99%

Spin-resolved photoemission study of epitaxially grown MoSe₂and WSe₂thin films

Mo¹,

Hwang²,

Zhang³

et al. 2016

J. Phys.: Condens. Matter

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Abstract. MoSe 2 and WSe 2 with a few layer thickness possess non-trivial spin texture with sizable spin splitting due to the inversion symmetry breaking embedded in the crystal structure and strong spin-orbit coupling. We report spinresolved photoemission study of the MoSe 2 and WSe 2 thin film samples epitaxially grown on bilayer graphene substrate. We found spin polarization only in singleand tri-layer samples, but not in bi-layer sample, mostly along the out-of-plane direction of the sample surface. The measured spin polarization is found to be strongly dependent on the light polarization as well as the measurement geometry, which reveals intricate coupling between spin and orbital degrees of freedom in this material class.

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“…This results in different orbital mixing within the same site, ε dxyd x 2 −y 2 ,↑ = ε d x 2 −y 2 dxy,↓ = iλ and ε dxyd x 2 −y 2 ,↓ = ε d x 2 −y 2 dxy,↑ = −iλ. We use 2λ = 150 meV, in good agreement with DFT calculations [5,45] and experimental values (152 meV [53], 138 meV [54] and 145 meV [55]). With this Hamiltonian and the right choice of boundaries, one can construct a flake like the triangle we consider [48,47,52].…”

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confidence: 77%

Long range of indirect exchange interaction on the edges of MoS₂flakes

Ávalos-Ovando¹,

Mastrogiuseppe²,

Ulloa³

2018

J. Phys.: Condens. Matter

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Abstract. We study the Ruderman-Kittel-Kasuya-Yosida interaction between two magnetic impurities connected to the edges of zigzag-terminated MoS 2 flakes. When the impurities lie on the edges of the flake, the effective exchange interaction exhibits sizable noncollinear Dzyaloshinskii-Moriya character that competes with a strong Ising coupling. We analyze the characteristic decay exponent for doping levels inside the band gap of the infinite layer, corresponding to edge states of the flake at the Fermi level. The characteristic exponents show sub-twodimensional (sub-2D) behavior for these band fillings, with decays much slower than quadratic. The Ising interaction has effectively one-dimensional (1D) long range, while the noncollinear component that grows for short impurity separation becomes comparable in magnitude. The resulting tunable exchange interaction on these systems opens the way for the study of interesting phases of impurity arrays with long-range stable helical order.arXiv:1607.08553v3 [cond-mat.mes-hall]

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Electronic Structure of Epitaxial Single-LayerMoS2

Cited by 162 publications

References 38 publications

Giant spin-splitting and gap renormalization driven by trions in single-layer WS2/h-BN heterostructures

Giant spin-splitting and gap renormalization driven by trions in single-layer WS2/h-BN heterostructures

Spin-resolved photoemission study of epitaxially grown MoSe₂and WSe₂thin films

Long range of indirect exchange interaction on the edges of MoS₂flakes

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Electronic Structure of Epitaxial Single-LayerMoS2

Cited by 162 publications

References 38 publications

Giant spin-splitting and gap renormalization driven by trions in single-layer WS2/h-BN heterostructures

Giant spin-splitting and gap renormalization driven by trions in single-layer WS2/h-BN heterostructures

Spin-resolved photoemission study of epitaxially grown MoSe2and WSe2thin films

Long range of indirect exchange interaction on the edges of MoS2flakes

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Product

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Spin-resolved photoemission study of epitaxially grown MoSe₂and WSe₂thin films

Long range of indirect exchange interaction on the edges of MoS₂flakes