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Journal ArticleDOI

Experimental evidence for type-II Dirac semimetal in PtSe 2

01 Sep 2017-Physical Review B (American Physical Society)-Vol. 96, Iss: 12, pp 125102
TL;DR: In this paper, the authors report the growth and characterization of high-quality single crystals and reveal the electronic structure to provide direct evidence for the existence of three-dimensional type-II Dirac fermions.
Abstract: While a monolayer ${\mathrm{PtSe}}_{2}$ film is a semiconductor with interesting spin structure, bulk ${\mathrm{PtSe}}_{2}$ crystal has been predicted to be a topological Dirac semimetal that can host a new type of Lorentz-violating Dirac fermions. Despite the intriguing predictions, experimental progress on the electronic structure of bulk ${\mathrm{PtSe}}_{2}$ has been hindered due to the lack of large, high-quality single-crystal samples. Here we report the growth and characterization of high-quality ${\mathrm{PtSe}}_{2}$ single crystals and reveal the electronic structure to provide direct evidence for the existence of three-dimensional type-II Dirac fermions. A comparison of the crystal, vibrational, and electronic structure to a related compound, ${\mathrm{PtTe}}_{2}$, is also discussed. Our work provides an important platform for exploring the novel quantum phenomena associated with type-II Dirac fermions in the $1T\ensuremath{-}{\mathrm{PtSe}}_{2}$ class of transition-metal dichalcogenides.
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Journal ArticleDOI
TL;DR: The structures of metallic transition metal dichalcogenides and their synthetic approaches for not only high-quality wafer-scale samples using conventional methods but also local small areas by a modification of the materials using Li intercalation, electron beam irradiation, light illumination, pressures, and strains are presented.
Abstract: Transition metal dichalcogenides are layered materials which are composed of transition metals and chalcogens of the group VIA in a 1:2 ratio. These layered materials have been extensively investigated over synthesis and optical and electrical properties for several decades. It can be insulators, semiconductors, or metals revealing all types of condensed matter properties from a magnetic lattice distorted to superconducting characteristics. Some of these also feature the topological manner. Instead of covering the semiconducting properties of transition metal dichalcogenides, which have been extensively revisited and reviewed elsewhere, here we present the structures of metallic transition metal dichalcogenides and their synthetic approaches for not only high-quality wafer-scale samples using conventional methods (e.g., chemical vapor transport, chemical vapor deposition) but also local small areas by a modification of the materials using Li intercalation, electron beam irradiation, light illumination, pr...

275 citations

Journal ArticleDOI
TL;DR: A high-performance ultra-broadband photodetector based on PdSe2 with unique pentagonal atomic structure with potential for future infrared optoelectronics and novel devices in which anisotropic properties are desirable is reported.
Abstract: Photodetection over a broad spectral range is crucial for optoelectronic applications such as sensing, imaging, and communication. Herein, a high-performance ultra-broadband photodetector based on PdSe2 with unique pentagonal atomic structure is reported. The photodetector responds from visible to mid-infrared range (up to ≈4.05 µm), and operates stably in ambient and at room temperature. It promises improved applications compared to conventional mid-infrared photodetectors. The highest responsivity and external quantum efficiency achieved are 708 A W-1 and 82 700%, respectively, at the wavelength of 1064 nm. Efficient optical absorption beyond 8 µm is observed, indicating that the photodetection range can extend to longer than 4.05 µm. Owing to the low crystalline symmetry of layered PdSe2 , anisotropic properties of the photodetectors are observed. This emerging material shows potential for future infrared optoelectronics and novel devices in which anisotropic properties are desirable.

192 citations

Journal ArticleDOI
TL;DR: In this article, the authors present a review of the topological semimetals (TSMs) from a chemistry perspective, and describe key features of TSMs, embedded in their electronic structure, and how they can be achieved.
Abstract: Initiated by the discovery of topological insulators, topologically non-trivial materials have attracted immense interest in the physics community in the past decade. One of the latest additions to the field, the material class of topological semimetals (TSMs), has grown at an extremely fast rate. While the prototype TSM, graphene, has been known for a while, the first 3D analogues of graphene have only been discovered recently. This Review, written from a chemistry perspective, intends to make the growing field of TSMs accessible to the wider community of materials scientists and scholars from related disciplines. To this end, we describe key features of TSMs, embedded in their electronic structure, and how they can be achieved based on chemical principles. We introduce the different classes of TSMs and review their salient representatives. Finally, selected properties and potential applications of these materials are discussed.

176 citations