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Tungsten ditelluride (WTe) is an atomically layered transition metal dichalcogenide whose physical properties change systematically from monolayer to bilayer and few-layer versions. In this report, we use apertureless scattering-type near-field optical microscopy operating at Terahertz (THz) frequencies and cryogenic temperatures to study the distinct THz range electromagnetic responses of mono-, bi- and trilayer WTe in the same multi-terraced micro-crystal. THz nano-images of monolayer terraces uncovered weakly insulating behavior that is consistent with transport measurements. The near-field signal on bilayer regions shows moderate metallicity with negligible temperature dependence. Subdiffractional THz imaging data together with theoretical calculations involving thermally activated carriers favor the semimetal scenario with [Formula: see text] over the semiconductor scenario for bilayer WTe. Also, we observed clear metallic behavior of the near-field signal on trilayer regions. Our data are consistent with the existence of surface plasmon polaritons in the THz range confined to trilayer terraces in our specimens. Finally, data for microcrystals up to 12 layers thick reveal how the response of a few-layer WTe asymptotically approaches the bulk limit.
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http://dx.doi.org/10.1038/s41467-021-23933-z | DOI Listing |
Nanoscale
July 2023
School of Physics, Beihang University, Beijing 100191, China.
WTe, as a member of Weyl semimetals, is a vital candidate for the development of broad-wavelength-range photodetectors. At present, the preparation of WTe films mainly depends on the chemical vapor deposition (CVD) method. However, the chemical reactivity between W and Te is low, and the controllable synthesis of large-sized layered WTe in a stoichiometric ratio is the main challenge for further research.
View Article and Find Full Text PDFDiscov Nano
March 2023
School of Physics and Electronics, Hunan Key Laboratory of Nanophotonics and Devices, Central South University, 932 South Lushan Road, Changsha, 410083, Hunan, People's Republic of China.
High-quality transition metal tellurides, especially for WTe, have been demonstrated to be necessarily synthesized under close environments and high temperatures, which are restricted by the low formation Gibbs free energy, thus limiting the electrochemical reaction mechanism and application studies. Here, we report a low-temperature colloidal synthesis of few-layer WTe nanostructures with lateral sizes around hundreds of nanometers, which could be tuned the aggregation state to obtain the nanoflowers or nanosheets by using different surfactant agents. The crystal phase and chemical composition of WTe nanostructures were analyzed by combining the characterization of X-ray diffraction and high-resolution transmission electron microscopy imaging and elements mapping.
View Article and Find Full Text PDFNat Commun
March 2023
Department of Physics and Astronomy, Seoul National University, Seoul, 08826, Korea.
Higher-order topological insulators are recently discovered quantum materials exhibiting distinct topological phases with the generalized bulk-boundary correspondence. T-WTe is a promising candidate to reveal topological hinge excitation in an atomically thin regime. However, with initial theories and experiments focusing on localized one-dimensional conductance only, no experimental reports exist on how the spin orientations are distributed over the helical hinges-this is critical, yet one missing puzzle.
View Article and Find Full Text PDFACS Nano
April 2023
Sorbonne Université, Muséum National d'Histoire Naturelle, UMR CNRS 7590, Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie, IMPMC, 75005 Paris, France.
MoTe has a stable hexagonal semiconducting phase (2H) as well as two semimetallic phases with monoclinic (1T') and orthorhombic (T) structures. A structural change can thus be accompanied by a significant change in electronic transport properties. The two semimetallic phases are connected by a temperature driven transition and could exhibit topological properties.
View Article and Find Full Text PDFNatl Sci Rev
December 2022
Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore637371, Singapore.
The second-order nonlinear Hall effect observed in the time-reversal symmetric system has not only shown abundant physical content, but also exhibited potential application prospects. Recently, a third-order nonlinear Hall effect has been observed in MoTe and WTe. However, few-layer MoTe and WTe are usually unstable in air and the observed third-order nonlinear Hall effect can be measured only at low temperature, which hinders further investigation as well as potential application.
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