Tuning the magnetoresistance of ultrathin WTe<sub>2</sub>sheets by electrostatic gating

Na, Junhong; Hoyer, Alexander; Schoop, Leslie M.; Weber, Daniel; Lotsch, Bettina V.; Burghard, Marko; Kern, Klaus

doi:10.1039/c6nr06327f

Cited by 26 publications

(35 citation statements)

References 32 publications

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“…The magnetoresistance of our thin films varies between 600% and 80% [see Fig. 1(f)], which is comparable to the largest MR reported in non-h-BN-encapsulated WTe 2 thinfilm samples with a similar thickness [28,29,31,32]. We also note that the mobility decreases as the sample thickness is reduced, as shown in Fig.…”

Section: Resultssupporting

confidence: 82%

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Thickness-dependent electronic structure in WTe2 thin films

Xiang

Srinivasan

et al. 2018

Phys. Rev. B

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X. (2018). Thickness-dependent electronic structure in WTe2 thin films. Physical Review B: Covering condensed matter and materials physics, 98 (3), 035115-1-035115-10. Thickness-dependent electronic structure in WTe2 thin films AbstractWe study the electronic structure of WTe2 thin films with different thicknesses. High-quality thin-film samples are obtained with carrier mobility up to 5000 cm2 V−1 s−1, which enables us to resolve the four main Fermi pockets from Shubnikov-de Haas (SdH) oscillations. Angle-resolved SdH oscillations show that the WTe2 thin films cross from three-dimensional to two-dimensional electronic systems at a thickness of ∼ 20 nm. Using the field effect, the nature of the Fermi pockets in thin-film WTe2 is identified, and the evolution of SdH oscillation frequencies is traced over different sample thicknesses. It is found that the frequencies dramatically decrease at a thickness of approximately 12 nm, which indicates the onset of finite-size effects on the band structure. Our work pins down two critical length scales of the thickness-dependent electronic structure in WTe2 thin films. Disciplines Engineering | Physical Sciences and Mathematics Publication DetailsXiang, F., Srinivasan, A., Du, Z. Z., Klochan, O., Dou, S., Hamilton, A. We study the electronic structure of WTe 2 thin films with different thicknesses. High-quality thin-film samples are obtained with carrier mobility up to 5000 cm 2 V −1 s −1 , which enables us to resolve the four main Fermi pockets from Shubnikov-de Haas (SdH) oscillations. Angle-resolved SdH oscillations show that the WTe 2 thin films cross from three-dimensional to two-dimensional electronic systems at a thickness of ∼ 20 nm. Using the field effect, the nature of the Fermi pockets in thin-film WTe 2 is identified, and the evolution of SdH oscillation frequencies is traced over different sample thicknesses. It is found that the frequencies dramatically decrease at a thickness of approximately 12 nm, which indicates the onset of finite-size effects on the band structure. Our work pins down two critical length scales of the thickness-dependent electronic structure in WTe 2 thin films.

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Section: Resultssupporting

confidence: 82%

“…We begin by characterizing the film quality to confirm that no obvious degradation happens during the sample fabrication and storage [27][28][29][30] and that they are of high enough quality to reveal the intrinsic electronic structure. Figures 1(a) all samples shown in Figs.…”

Section: Resultsmentioning

confidence: 99%

Thickness-dependent electronic structure in WTe2 thin films

Xiang

Srinivasan

et al. 2018

Phys. Rev. B

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“…[11] Despite the unique merits of monolayers, multilayers, which consist of multiple conducting monolayers, may be a better candidate for most 2D layered materials because of their higher carrier mobility and larger current density compared to monolayers, with respect to applications in electronic devices. [3,6,12,13] Previous theoretical and experimental investigations have clearly demonstrated that the effective mass increases with bandgap energy as thickness reduced. [14] In addition, the adjacent surface phonon and numerous Coulomb scatterers that surround atomically thin channel materials further degrade the intrinsic carrier mobility, [15,16] implying the disadvantage of monolayer platform as a transistor.…”

Section: Doi: 101002/adma201805860mentioning

confidence: 99%

“…and other mono-elemental materials (e.g., black phosphorus, tellurene, etc.) [3,6,12,13] Previous theoretical and experimental investigations have clearly demonstrated that the effective mass increases with bandgap energy as thickness reduced. [2][3][4][5][6] In particular, atomically thin monolayers have proven to be an ideal platform for the exploration of the unique features associating with 2D electronic systems such as ultrahigh mobility, [7] quantum phase transition, [8] indirect exciton condensation, [9] quantum oscillation, [10] and the quantum Hall effect.…”

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confidence: 99%

Probing Distinctive Electron Conduction in Multilayer Rhenium Disulfide

Lee

Choi

et al. 2018

Advanced Materials

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WSe 2 , etc.) and other mono-elemental materials (e.g., black phosphorus, tellurene, etc.) have generated significant interest in numerous research fields. [2][3][4][5][6] In particular, atomically thin monolayers have proven to be an ideal platform for the exploration of the unique features associating with 2D electronic systems such as ultrahigh mobility, [7] quantum phase transition, [8] indirect exciton condensation, [9] quantum oscillation, [10] and the quantum Hall effect. [11] Despite the unique merits of monolayers, multilayers, which consist of multiple conducting monolayers, may be a better candidate for most 2D layered materials because of their higher carrier mobility and larger current density compared to monolayers, with respect to applications in electronic devices. [3,6,12,13] Previous theoretical and experimental investigations have clearly demonstrated that the effective mass increases with bandgap energy as thickness reduced. [14] In addition, the adjacent surface phonon and numerous Coulomb scatterers that surround atomically thin channel materials further degrade the intrinsic carrier mobility, [15,16] implying the disadvantage of monolayer platform as a transistor.Among the various families of 2D layered materials, a multilayer rhenium disulfide (ReS 2 ) has recently garnered notable attention because of their three unique properties compared to other TMD materials; i) anisotropic in-plane transport, ii) direct bandgap, and iii) layer-independent electronic band structure. [17] The distorted octahedral (1T′) structure of ReS 2 is responsible for the anisotropic in-plane transport property. [18][19][20] The layer-independent electronic band structure with direct bandgap is linked to a decoupled vdW interaction between adjacent layers, [21] leading to a much higher interlayer resistivity of bulk ReS 2 [22] compared to that of the other TMDs [23] including MoS 2 . [24] This fact implies that few-layered ReS 2 is the potentially a superior platform for studying intrinsic carrier transport features of multilayer systems. This is because the interlayer resistivity governs the charge distribution along the channel thickness [25] and the channel access resistance, in addition to the Thomas-Fermi charge screening length.Herein, we report on the distinctive electron conduction mechanism of few-layered 1T′ ReS 2 by presenting; i) the anisotropic carrier transport, ii) modification of charge distribution Charge carrier transport in multilayer van der Waals (vdW) materials, which comprise multiple conducting layers, is well described using Thomas-Fermi charge screening (λ TF ) and interlayer resistance (R int ). When both effects occur in carrier transport, a channel centroid migrates along the c-axis according to a vertical electrostatic force, causing redistribution of the conduction centroid in a multilayer system, unlike a conventional bulk material. Thus far, numerous unique properties of vdW materials are discovered, but direct evidence for distinctive charge transport behavior in 2D layered materi...

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“…The crystal structure of WTe 2 consists of weaklybonded block-layers of W-Te atoms along the c direction. The layered nature of WTe 2 has facilitated the fabrication of devices based on thin layers of WTe 2 , enabling the application of gate voltage, and hence further exploration of fundamental physical properties in a controllable manner [8,[13][14][15][16].…”

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Nearly isotropic superconductivity in the layered Weyl semimetal WTe2 at 98.5 kbar

et al. 2017

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Layered transition metal dichalcogenide WTe2 has recently attracted significant attention due to the discovery of an extremely large magnetoresistance, a predicted type-II Weyl semimetallic state, and the pressure-induced superconducting state. By a careful measurement of the superconducting upper critical fields as a function of the magnetic field angle at a pressure as high as 98.5 kbar, we provide the first detailed examination of the dimensionality of the superconducting condensate in WTe2. Despite the layered crystal structure, the upper critical field exhibits a negligible field anisotropy. The angular dependence of the upper critical field can be satisfactorily described by the anisotropic mass model from 2.2 K (T /Tc ∼ 0.67) to 0.03 K (T /Tc ∼ 0.01), with a practically identical anisotropy factor γ ∼ 1.7. The temperature dependence of the upper critical field, determined for both H ⊥ ab and H // ab, can be understood by a conventional orbital depairing mechanism. Comparison of the upper critical fields along the two orthogonal field directions results in the same value of γ ∼ 1.7, leading to a temperature independent anisotropy factor from near Tc to < 0.01Tc. Our findings thus identify WTe2 as a nearly isotropic superconductor, with an anisotropy factor among one of the lowest known in superconducting transition metal dichalcogenides.The discovery of an extremely large and non-saturating magnetoresistance in semimetallic WTe 2 [1] has generated considerable research efforts [2][3][4][5][6][7][8][9][10][11]. The interest is further intensified with the prediction that WTe 2 can be a type-II Weyl semimetal, in which Weyl fermions emerge at the border between electron and hole pockets [12]. The crystal structure of WTe 2 consists of weaklybonded block-layers of W-Te atoms along the c direction. The layered nature of WTe 2 has facilitated the fabrication of devices based on thin layers of WTe 2 , enabling the application of gate voltage, and hence further exploration of fundamental physical properties in a controllable manner [8,[13][14][15][16].Another powerful tool to tune the properties of WTe 2 is pressure. With the application of pressure, superconductivity has been successfully induced in the bulk WTe 2 [17,18]. Although the temperature-pressure phase diagrams reported by two groups [17,18] are quite different, some qualitative similarities can still be observed. First, the superconducting transition temperature (T c ) takes a dome-shaped pressure dependence, with a maximum onset T c between 6.5 K and 7 K. Second, the magnetoresistance is significantly suppressed when the superconducting state sets in. In the work of Pan et al.[17], superconductivity can be induced with a pressure as low as ∼25 kbar, which is close to the pressure range where a subtle structural transformation from T d phase to 1T phase was detected via powder X-ray diffraction and Raman spectroscopy [19,20]. However, these results contradict the study of Kang et al. [18], which claims that the structure * skgoh@phy.cuhk.edu.hk of WTe...

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Tuning the magnetoresistance of ultrathin WTe₂sheets by electrostatic gating

Cited by 26 publications

References 32 publications

Thickness-dependent electronic structure in WTe2 thin films

Thickness-dependent electronic structure in WTe2 thin films

Probing Distinctive Electron Conduction in Multilayer Rhenium Disulfide

Nearly isotropic superconductivity in the layered Weyl semimetal WTe2 at 98.5 kbar

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Tuning the magnetoresistance of ultrathin WTe2sheets by electrostatic gating

Cited by 26 publications

References 32 publications

Thickness-dependent electronic structure in WTe2 thin films

Thickness-dependent electronic structure in WTe2 thin films

Probing Distinctive Electron Conduction in Multilayer Rhenium Disulfide

Nearly isotropic superconductivity in the layered Weyl semimetal WTe2 at 98.5 kbar

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Tuning the magnetoresistance of ultrathin WTe₂sheets by electrostatic gating