Anisotropic Optical Response of WTe2 Single Crystals Studied by Ellipsometric Analysis

Buchkov, K.; Todorov, R.; Terziyska, P.; Gospodinov, M.; Strijkova, Velichka; Dimitrov, Dimitre; Marinova, Vera

doi:10.3390/nano11092262

Cited by 10 publications

(4 citation statements)

References 62 publications

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“…The graphene-WTe 2 device fabrication follows the protocols established with other TMDCs [30] (see supplementary information (available online at stacks.iop.org/TDM/9/035014/mmedia)). The WTe 2 crystals were grown by chemical vapor transport, using bromine as a transport agent [57]. Their electronic and crystalline structure was investigated by x-ray photoelectron spectroscopy, angle-resolved photoemission spectroscopy, and Raman spectroscopy, all of them demonstrating high quality and confirming the Td phase (see supplementary material).…”

Section: Csi In Graphene-wtementioning

confidence: 99%

Resolving spin currents and spin densities generated by charge-spin interconversion in systems with reduced crystal symmetry

et al. 2022

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The ability to control the generation of spins in arbitrary directions is a long-sought goal in spintronics. Charge to spin interconversion (CSI) phenomena depend strongly on symmetry. Systems with reduced crystal symmetry allow anisotropic CSI with unconventional components, where charge and spin currents and the spin polarization are not mutually perpendicular to each other. Here, we demonstrate experimentally that the CSI in graphene-WTe2 induces spins with components in all three spatial directions. By performing multi-terminal nonlocal spin precession experiments, with specific magnetic fields orientations, we discuss how to disentangle the CSI from the spin Hall and inverse spin galvanic effects.

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Section: Csi In Graphene-wtementioning

confidence: 99%

Resolving spin currents and spin densities generated by charge-spin interconversion in systems with reduced crystal symmetry

et al. 2022

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“…It enables characterization of domain boundaries that are generally challenging to detect. The method can be applied to thin films of other optical anisotropic compounds, like SnS, black phosphorus, and WTe 2 (Supporting Information).…”

Section: Resultsmentioning

confidence: 99%

Measuring and Then Eliminating Twin Domains in SnSe Thin Films Using Fast Optical Metrology and Molecular Beam Epitaxy

et al. 2022

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van der Waals (vdW) layered chalcogenides have strongly direction-dependent (i.e., anisotropic) properties that make them interesting for photonic and optoelectronic applications. Orthorhombic tin selenide (α-SnSe) is a triaxial vdW material with strong optical anisotropy within layer planes, which has motivated studies of optical phase and domain switching. As with every vdW material, controlling the orientation of crystal domains during growth is key to reliably making wafer-scale, high-quality thin films, free from twin boundaries. Here, we demonstrate a fast optical method to quantify domain orientation in SnSe thin films made by molecular beam epitaxy (MBE). The in-plane optical anisotropy results in white-light being reflected into distinct colors for certain optical polarization angles and the color depends on domain orientation. We use our method to confirm a high density of twin boundaries in SnSe epitaxial films on MgO substrates, with square symmetry that results in degeneracy between SnSe 90° domain orientations. We then demonstrate that growing on a-plane sapphire, with rectangular lattice-matched symmetry that breaks the SnSe domain degeneracy, results in single-crystalline films with one preferred orientation. Our SnSe bottom-up film synthesis by MBE enables future applications of this vdW material that is particularly difficult to process by top-down methods. Our optical metrology is fast and can apply to all triaxial vdW materials.

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“…It was predicted that some of the anisotropic 2D materials present hyperbolic surface plasmon polaritons but have not been confirmed experimentally yet 16 . Recently, – thin film has been reported as a semimetal with in-plane anisotropy due to the interplay of its intraband and interband electronic transitions 8 , 17 – 19 . In other words, both free carrier response and bound interband transitions characterize the amount of anisotropy that leads to intrinsic tunability.…”

Section: Introductionmentioning

confidence: 99%

Polarization dependent light propagation in $$\textrm{WTe}_2$$ multilayer structure

Abdol

Shojaei

Abdollahipour

2023

Sci Rep

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Abstract$$\textrm{WTe}_2$$ WTe 2 is one of the exciting and outstanding semimetallic members of TMDCs, which has attracted immense attention for manipulating light propagation due to its inherent optical anisotropy and hyperbolic characteristic in the infrared frequency range. We investigate the dependence of the reflectance and transmittance of structures with a single and double $$\textrm{WTe}_2$$ WTe 2 thin film in terms of frequency and polarization angle of the incident wave. We find rich behaviors in the optical response of these structures due to their anisotropic permittivity tensors. Furthermore, we analyze the polarization state of transmitted and reflected waves through these structures. We demonstrate that these structures provide the ability to achieve desired polarization rotation for outgoing waves by tuning the frequency and polarization angle of the incident wave with respect to the principal axes of $$\textrm{WTe}_2$$ WTe 2 thin film. In particular, we elucidate the essential relevance of the optical response and polarization rotation of the double thin film structure to the in-plain twist angle of $$\textrm{WTe}_2$$ WTe 2 thin films. We explain that this structure permits comprehensive control of the polarization rotation of the outgoing waves by adjusting the twist angle of thin films. The proposed structure can be employed as an efficient light manipulator with the aim of application in communication, imaging, and information processing.

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Anisotropic Optical Response of WTe2 Single Crystals Studied by Ellipsometric Analysis

Cited by 10 publications

References 62 publications

Resolving spin currents and spin densities generated by charge-spin interconversion in systems with reduced crystal symmetry

Resolving spin currents and spin densities generated by charge-spin interconversion in systems with reduced crystal symmetry

Measuring and Then Eliminating Twin Domains in SnSe Thin Films Using Fast Optical Metrology and Molecular Beam Epitaxy

Polarization dependent light propagation in $$\textrm{WTe}_2$$ multilayer structure

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