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Natural topological transitions and Luttinger-liquid plasmons in two-dimensional WTe2 crystals in the Terahertz range

Grant number: 23/09839-5
Support Opportunities:Scholarships in Brazil - Post-Doctoral
Effective date (Start): April 01, 2024
Effective date (End): March 31, 2026
Field of knowledge:Physical Sciences and Mathematics - Physics - Condensed Matter Physics
Principal Investigator:Raul de Oliveira Freitas
Grantee:Flávio Henrique Feres
Host Institution: Centro Nacional de Pesquisa em Energia e Materiais (CNPEM). Ministério da Ciência, Tecnologia e Inovação (Brasil). Campinas , SP, Brazil
Associated research grant:19/14017-9 - From excitons waves to THz-phonons: 2Ds materials nano-optics via synchrotron infrared nanospectroscopy, AP.JP


Tungsten Telluride (WTe2) is a semimetal belonging to Weyl type II topological class. In addition to having extraordinary electronic characteristics, it is a lamellar material that can be produced in the form of two-dimensional crystals via mechanical exfoliation. Recently, the ability of WTe2 to sustain plasmonic modes was demonstrated by means of infrared nanospectroscopy. Intriguingly, in specific far-infrared ranges (429 cm-1 - 623 cm-1), WTe2 exhibits hyperbolic polariton plasmons due to its in-plane anisotropic conductivity. From a theoretical perspective, the possibility of natural channeling of plasmon polaritons mediated by a topological transition is observed. Recently, the channeling of polaritons has been demonstrated through sophisticated nanofabrication of heterostructures, as in the case of spun crystals of molybdenum trioxide (MoO3). As an alternative to the intrinsic challenges of the fabrication process of such structures, WTe2 appears as a simpler way, since the channeling process occurs naturally in certain spectral bands. Nevertheless, recent studies with twisted layers of WTe2 demonstrated the formation of nanowire arrays through Moiré patterns in its crystalline lattice. The presence of these nanowires makes it possible to investigate phenomena known as Luttinger Liquids, which occur in one-dimensional conductors. Although Luttinger Liquids have been widely studied using carbon nanotubes, this project will investigate the plasmonic modes of Luttinger Liquids restricted to the Moiré pattern formed by twisted layers of WTe2 in the mid-infrared, far-infrared and terahertz ranges. To investigate this phenomenon, advanced spectroscopy and nanoscale imaging techniques will be used, such as SINS and s-SNOM, using quantum cascade lasers and the fourth-generation Sirius synchrotron at LNLS as light sources, with great possibility of producing pioneering results in this new area called "twistoptics". (AU)

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