Detection of Weyl Fermions and the Metal to Weyl-Semimetal phase transition in WTe$_2$ via broadband High Resolution NMR
Authors:
Wassilios Papawassiliou,
José P. Carvalho,
Hae Jin Kim,
Chang-Yeon Kim,
Seung Jo Yoo,
Jin Bae Lee,
Saeed Alhassan,
Savvas Orfanidis,
Vassilios Psycharis,
Marina Karagianni,
Michael Fardis,
Nikolaos Panopoulos,
Georgios Papavassiliou,
Andrew J. Pell
Abstract:
Weyl Fermions (WFs) in the type-II Weyl Semimetal (WSM) WTe$_2$ are difficult to resolve experimentally because the Weyl bands disperse in an extremely narrow region of the (E-k) space. Here, by using DFT-assisted high-resolution $^{125}$Te solid-state NMR (ssNMR) in the temperature range $50$K - $700$K, we succeeded in detecting low energy WF excitations and monitor their evolution with temperatu…
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Weyl Fermions (WFs) in the type-II Weyl Semimetal (WSM) WTe$_2$ are difficult to resolve experimentally because the Weyl bands disperse in an extremely narrow region of the (E-k) space. Here, by using DFT-assisted high-resolution $^{125}$Te solid-state NMR (ssNMR) in the temperature range $50$K - $700$K, we succeeded in detecting low energy WF excitations and monitor their evolution with temperature. Remarkably, WFs appear to emerge at T$\sim 120$K; at lower temperatures WTe$_2$ behaves as a metal. This intriguing metal-to-WSM phase transition is shown to be induced by the rapid raise of the Fermi level with temperature, crossing solely the electron and hole pockets in the low-T metallic phase, while crossing the Weyl bands near the nodal points - a prerequisite for the emergence of WFs - only for T$>120$K.
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Submitted 6 December, 2021; v1 submitted 4 October, 2021;
originally announced October 2021.
Template Dissolution Interfacial Patterning of Single Colloids for Nanoelectrochemistry and Nanosensing
Authors:
Joong Bum Lee,
Harriet Walker,
Yi Li,
Tae Won Nam,
Aliaksandra Rakovich,
Riccardo Sapienza,
Yeon Sik Jung,
Yoon Sung Nam,
Stefan A. Maier,
Emiliano Cortés
Abstract:
Deterministic positioning and assembly of colloidal nanoparticles (NPs) onto substrates is a core requirement and a promising alternative to top down lithography to create functional nanostructures and nanodevices with intriguing optical, electrical, and catalytic features. Capillary-assisted particle assembly (CAPA) has emerged as an attractive technique to this end, as it allows controlled and s…
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Deterministic positioning and assembly of colloidal nanoparticles (NPs) onto substrates is a core requirement and a promising alternative to top down lithography to create functional nanostructures and nanodevices with intriguing optical, electrical, and catalytic features. Capillary-assisted particle assembly (CAPA) has emerged as an attractive technique to this end, as it allows controlled and selective assembly of a wide variety of NPs onto predefined topographical templates using capillary forces. One critical issue with CAPA, however, lies in its final printing step, where high printing yields are possible only with the use of an adhesive polymer film. To address this problem, we have developed a template dissolution interfacial patterning (TDIP) technique to assemble and print single colloidal AuNP arrays onto various dielectric and conductive substrates in the absence of any adhesion layer, with printing yields higher than 98%. The TDIP approach grants direct access to the interface between the AuNP and the target surface, enabling the use of colloidal AuNPs as building blocks for practical applications. The versatile applicability of TDIP is demonstrated by the creation of direct electrical junctions for electro- and photoelectrochemistry and nanoparticle-on-mirror geometries for single particle molecular sensing.
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Submitted 25 August, 2021;
originally announced September 2021.