Chemical stability of tellurides of subgroup VIa transition metals in various corrosive media

Obolonchik, V. A.; Vainer, L. S.; Yanaki, A.A.

doi:10.1007/bf00801271

Cited by 8 publications

(4 citation statements)

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“…Bulk WTe 2 : Bulk WTe 2 crystallizes in the inversion breaking bulk − T d structure, as consistently found in all x-ray studies [49][50][51][52][53].…”

Section: Experimental Estimation Of the Berry Curvature Dipolesupporting

confidence: 72%

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Electrically switchable Berry curvature dipole in the monolayer topological insulator WTe2

et al. 2018

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Recent experimental evidence for the quantum spin Hall (QSH) state in monolayer WTe 2 has linked the fields of twodimensional materials and topological physics [1][2][3][4][5][6][7] . This twodimensional topological crystal also displays unconventional spin-torque 8 and gate-tunable superconductivity 7 . Whereas the realization of the QSH has demonstrated the nontrivial topology of the electron wavefunctions of monolayer WTe 2 , the geometrical properties of the wavefunction, such as the Berry curvature 9 , remain unstudied. Here we utilize mid-infrared optoelectronic microscopy to investigate the Berry curvature in monolayer WTe 2 . By optically exciting electrons across the inverted QSH gap, we observe an in-plane circular photogalvanic current even under normal incidence. The application of an out-of-plane displacement field allows further control of the direction and magnitude of the photocurrent. The observed photocurrent reveals a Berry curvature dipole that arises from the nontrivial wavefunctions near the inverted gap edge. The Berry curvature dipole and strong electric field effect are enabled by the inverted band structure and tilted crystal lattice of monolayer WTe 2 . Such an electrically switchable Berry curvature dipole may facilitate the observation of a wide range of quantum geometrical phenomena such as the quantum nonlinear Hall 10,11 , orbital-Edelstein 12 and chiral polaritonic effects 13,14 . One of the early landmarks of condensed matter physics was the classification of metals, insulators and semiconductors by studying the energy-momentum dispersion-or band structure-of the electrons in crystalline solids. Despite this remarkable success, the quantum nature of the electron states means that they can only be fully described by their quantum wavefunctions, whereas the band structure concerns only the energy and momentum eigenvalues of the wavefunctions. Therefore, a central question in modern condensed matter physics is whether there exist new phenomena that arise from other properties of quantum wavefunctions beyond the band structure 9 . For instance, the study of the global-or topological-properties of electronic wavefunctions continues to give rise to novel topological phases, including the QSH states, three-dimensional topological insulators and Weyl semimetals. These topological materials feature robust surface states and often exhibit protected transport and optical responses. Another direction is to study the local-or geometrical-properties of wavefunctions. One important property is the local curvature of the wavefunction, defined as the Berry curvature. Originally employed to explain the anomalous Hall conductivities of ferromagnets 9 , the importance of the Berry curvature is increasingly recognized in a wide range of areas in condensed matter physics, including nonlocal transport and chiral optical responses in noncentrosymmetric metals and semiconductors [10][11][12][15][16][17][18][19][20] , unconventional pairing in superconductors 21 , and topological plasmonic and excitonic ...

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“…Bulk WTe 2 : Bulk WTe 2 crystallizes in the inversion breaking bulk − T d structure, as consistently found in all x-ray studies [49][50][51][52][53].…”

Section: Experimental Estimation Of the Berry Curvature Dipolesupporting

confidence: 72%

“…Therefore, bulk − T d is an inversion breaking, orthorhombic phase. We now discuss the crystal structures of bulk WTe 2 and MoTe 2 , both of which have been determined by extensive x-ray studies [49][50][51][52][53][54][55][56][57][58][59][60][61].…”

Section: Experimental Estimation Of the Berry Curvature Dipolementioning

confidence: 99%

Electrically switchable Berry curvature dipole in the monolayer topological insulator WTe2

et al. 2018

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“…50,51 Other TEM-based thickness measurement methods utilize analysis of convergent beam electron diffraction (CBED) patterns, 52 diffraction or imaging tilt series, [53][54][55][56][57][58] or low-loss electron energy-loss spectroscopy (EELS). 59 Yet, these methods do not extract the information directly from a single atomic-resolution image, which would be desirable for ease of acquisition and analysis, especially because WTe 2 is highly air sensitive, [60][61][62][63][64][65] and to minimize the electron dose that damages beam-sensitive 2D materials. Additionally, a direct method would enable precise analysis at or near atomic-scale defects sites, despite local variations in thickness that can result from thin-film growth methods, such as CVD or MBE.…”

Section: Introductionmentioning

confidence: 99%

Quantifying the thickness of WTe2 using atomic-resolution STEM simulations and supervised machine learning

Dihingia,

Vázquez-Lizardi,

et al. 2024

The Journal of Chemical Physics

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For two-dimensional (2D) materials, the exact thickness of the material often dictates its physical and chemical properties. The 2D quantum material WTe2 possesses properties that vary significantly from a single layer to multiple layers, yet it has a complicated crystal structure that makes it difficult to differentiate thicknesses in atomic-resolution images. Furthermore, its air sensitivity and susceptibility to electron beam-induced damage heighten the need for direct ways to determine the thickness and atomic structure without acquiring multiple measurements or transferring samples in ambient atmosphere. Here, we demonstrate a new method to identify the thickness up to ten van der Waals layers in Td-WTe2 using atomic-resolution high-angle annular dark-field scanning transmission electron microscopy image simulation. Our approach is based on analyzing the intensity line profiles of overlapping atomic columns and building a standard neural network model from the line profile features. We observe that it is possible to clearly distinguish between even and odd thicknesses (up to seven layers), without using machine learning, by comparing the deconvoluted peak intensity ratios or the area ratios. The standard neural network model trained on the line profile features allows thicknesses to be distinguished up to ten layers and exhibits an accuracy of up to 94% in the presence of Gaussian and Poisson noise. This method efficiently quantifies thicknesses in Td-WTe2, can be extended to related 2D materials, and provides a pathway to characterize precise atomic structures, including local thickness variations and atomic defects, for few-layer 2D materials with overlapping atomic column positions.

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“…Experimental (b, c) and simulated (d, e) HAADF-STEM images and FFT patterns for monolayer WTe 2 . Simulated electron diffraction patterns used the structural information from ref .…”

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confidence: 99%

Atomic Resolution Imaging of Highly Air-Sensitive Monolayer and Twisted-Bilayer WTe₂

et al. 2023

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Bulk Td-WTe 2 is a semimetal, while its monolayer counterpart is a two-dimensional (2D) topological insulator. Recently, electronic transport resembling a Luttinger liquid state was found in twisted-bilayer WTe 2 (tWTe 2 ) with a twist angle of ∼5°. Despite the strong interest in 2D WTe 2 systems, little experimental information is available about their intrinsic microstructure, leaving obstacles in modeling their physical properties. The monolayer, and consequently tWTe 2 , are highly air-sensitive, and therefore, probing their atomic structures is difficult. In this study, we develop a robust method for atomic-resolution visualization of monolayers and tWTe 2 obtained through mechanical exfoliation and fabrication. We confirm the high crystalline quality of mechanically exfoliated WTe 2 samples and observe that tWTe 2 with twist angles of ∼5 and ∼2°retains its pristine moiréstructure without substantial deformations or reconstructions. The results provide a structural foundation for future electronic modeling of monolayer and tWTe 2 moirélattices.

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Chemical stability of tellurides of subgroup VIa transition metals in various corrosive media

Cited by 8 publications

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Electrically switchable Berry curvature dipole in the monolayer topological insulator WTe2

Electrically switchable Berry curvature dipole in the monolayer topological insulator WTe2

Quantifying the thickness of WTe2 using atomic-resolution STEM simulations and supervised machine learning

Atomic Resolution Imaging of Highly Air-Sensitive Monolayer and Twisted-Bilayer WTe₂

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Chemical stability of tellurides of subgroup VIa transition metals in various corrosive media

Cited by 8 publications

References 0 publications

Electrically switchable Berry curvature dipole in the monolayer topological insulator WTe2

Electrically switchable Berry curvature dipole in the monolayer topological insulator WTe2

Quantifying the thickness of WTe2 using atomic-resolution STEM simulations and supervised machine learning

Atomic Resolution Imaging of Highly Air-Sensitive Monolayer and Twisted-Bilayer WTe2

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Atomic Resolution Imaging of Highly Air-Sensitive Monolayer and Twisted-Bilayer WTe₂