Thermodynamic properties of tungsten ditelluride (WTe2) I. The preparation and lowtemperature heat capacity at temperatures from 6 K to 326 K

Callanan, Jane E.; Hope, Gregory Alan; Weir, Ron D.; Westrum, Edgar F.

doi:10.1016/s0021-9614(05)80034-5

Cited by 43 publications

(32 citation statements)

References 46 publications

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“…2a),344041424450 using bromine (Br) as the transport agent. Following the synthesis, the powder and bulk crystals were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and temperature-dependent current-voltage (I-V) measurements.…”

Section: Resultsmentioning

confidence: 99%

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Tungsten Ditelluride: a layered semimetal

Lee

Cruz‐Silva

Calderín

et al. 2015

Sci Rep

215

176

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Tungsten ditelluride (WTe2) is a transition metal dichalcogenide (TMD) with physical and electronic properties that make it attractive for a variety of electronic applications. Although WTe2 has been studied for decades, its structure and electronic properties have only recently been correctly described. We experimentally and theoretically investigate the structure, dynamics and electronic properties of WTe2, and verify that WTe2 has its minimum energy configuration in a distorted 1T structure (Td structure), which results in metallic-like transport. Our findings unambiguously confirm the metallic nature of WTe2, introduce new information about the Raman modes of Td-WTe2, and demonstrate that Td-WTe2 is readily oxidized via environmental exposure. Finally, these findings confirm that, in its thermodynamically favored Td form, the utilization of WTe2 in electronic device architectures such as field effect transistors may need to be reevaluated.

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Section: Resultsmentioning

confidence: 99%

“…Both 2H3738 and Td structures35394041424344 have been reported in experimental studies of WTe 2 , and recent reports have focused on the extraordinary magnetoresistance353645 and thermoelectric3245 properties of Td-WTe 2 . In this paper, we study bulk and exfoliated, crystalline WTe 2 synthesized under near equilibrium conditions.…”

mentioning

confidence: 99%

Tungsten Ditelluride: a layered semimetal

Lee

Cruz‐Silva

Calderín

et al. 2015

Sci Rep

215

176

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“…All these results are consistent with the topologically trivial nature of WTe 2 . Notice that WTe 2 and MoTe 2 have very similar phonon dispersions [30] and comparable Debye [31,32] and superconducting [33,34] temperatures. Hence, electronphonon coupling alone cannot explain the different temperature dependence measured in the two materials.…”

Section: (C)mentioning

confidence: 99%

Enhanced ultrafast relaxation rate in the Weyl semimetal phase of MoTe2 measured by time- and angle-resolved photoelectron spectroscopy

et al. 2017

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MoTe2 has recently been shown to realize in its low-temperature phase the type-II Weyl semimetal (WSM). We investigated by time-and angle-resolved photoelectron spectroscopy (tr-ARPES) the possible influence of the Weyl points in the electron dynamics above the Fermi level EF, by comparing the ultrafast response of MoTe2 in the trivial and topological phases. In the low-temperature WSM phase, we report an enhanced relaxation rate of electrons optically excited to the conduction band, which we interpret as a fingerprint of the local gap closure when Weyl points form. By contrast, we find that the electron dynamics of the related compound WTe2 is slower and temperature-independent, consistent with a topologically trivial nature of this material. Our results shows that tr-ARPES is sensitive to the small modifications of the unoccupied band structure accompanying the structural and topological phase transition of MoTe2.The recent discovery of Weyl fermions as low-energy quasiparticles in TaAs [1][2][3] and other related compounds [4,5] has boosted the interest in topological semimetals (TSMs) [6]. Type-II Weyl semimetals (WSMs) are a novel class of materials that host fermions violating Lorentz invariance [7]. These quasiparticles are realized in the strongly tilted cones that form in momentum space around special Weyl points (WPs) where the valence and conduction bands touch. WTe 2 [7] and MoTe 2 [8-10] have been proposed as possible type-II WSMs. While the topological phase of WTe 2 is still under debate, the existence of the WSM phase in the low temperature non-centrosymmetric structure of MoTe 2 is supported by the observation of surface Fermi arcs [11][12][13][14][15]. The Weyl points, however, are located above the Fermi level E F and this hinders a direct observation by conventional angle-resolved photoelectron spectroscopy (ARPES). To circumvent this difficulty, one would need a probe that is sensitive to the presence/absence of small energy band gaps in the unoccupied density of states.In this Letter we show that time-and angle-resolved photoelectron spectroscopy (tr-ARPES) can provide such information. We report a shortening of the relaxation time in the gapless type-II Weyl phase of MoTe 2 , which reflects the enhanced interband scattering from the conduction band (CB) to the valence band (VB) mediated by electron -electron scattering along the Weyl cone. These scattering processes are active only when the band gap is locally closed. This conclusion is supported by the observation of a slower, temperatureindependent dynamics in WTe 2 , indicative of a local direct band gap, which acts as an effective bottleneck for the electron relaxation.MoTe 2 is a layered material. It can be cleaved to expose large flat (001) terraces, ideal for ARPES studies. Figure 1 illustrates the WSM phase, which is only realized in the lowtemperature orthorhombic (space group Pmn2 1 ) structurehereafter referred to as the 1T' phase [17] -where inversion symmetry is broken. The crystal structure is sketched in Fig. 1 (a), along wi...

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“…According to the classical theory [23,24], WTe 2 should possess lower thermal conductivity than WSe 2 due to the heavier atom mass and lower Debye temperature in WTe 2 . However, unlike the electronic properties of WTe 2 , which have been intensively explored, the study on the thermal properties is still in its infancy [25][26][27][28]. The experiment measurement showed the thermal conductivity of polycrystalline WTe 2 is 0.8 W m −1 K −1 [28], which didn't exhibit the anisotropy of thermal transport.…”

Section: Introductionmentioning

confidence: 99%

First-principles study of lattice thermal conductivity of Td–WTe₂

et al. 2016

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The structural and thermal properties of bulk Td-WTe 2 have been studied by using first-principles calculations based on the simple Klemens model and an iterative self-consistent method. Both methods show that lattice thermal conductivity is anisotropic, with the highest value in the (001) plane, and lowest one along the c-axis at 300 K. The calculated average thermal conductivity of WTe 2 is in agreement with the experimental measurement. The size dependent thermal conductivity shows that nanostructuring of WTe 2 can possibly further decrease the lattice thermal conductivity, which can improve the thermoelectric efficiency. Such extremely low thermal conductivity, even much lower than WSe 2 , makes WTe 2 having many potential applications in thermal insulation and thermoelectric materials.

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Thermodynamic properties of tungsten ditelluride (WTe2) I. The preparation and lowtemperature heat capacity at temperatures from 6 K to 326 K

Cited by 43 publications

References 46 publications

Tungsten Ditelluride: a layered semimetal

Tungsten Ditelluride: a layered semimetal

Enhanced ultrafast relaxation rate in the Weyl semimetal phase of MoTe2 measured by time- and angle-resolved photoelectron spectroscopy

First-principles study of lattice thermal conductivity of Td–WTe₂

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Thermodynamic properties of tungsten ditelluride (WTe2) I. The preparation and lowtemperature heat capacity at temperatures from 6 K to 326 K

Cited by 43 publications

References 46 publications

Tungsten Ditelluride: a layered semimetal

Tungsten Ditelluride: a layered semimetal

Enhanced ultrafast relaxation rate in the Weyl semimetal phase of MoTe2 measured by time- and angle-resolved photoelectron spectroscopy

First-principles study of lattice thermal conductivity of Td–WTe2

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First-principles study of lattice thermal conductivity of Td–WTe₂