Kitkaite NiTeSe, an Ambient-Stable Layered Dirac Semimetal with Low-Energy Type-II Fermions with Application Capabilities in Spintronics and Optoelectronics

Abstract

The emergence of Dirac semimetals has stimulated growing attention, owing to the considerable technological potential arising from their peculiar exotic quantum transport related to their nontrivial topological states. Especially, materials showing type-II Dirac fermions afford novel device functionalities enabled by anisotropic optical and magnetotransport properties. Nevertheless, real technological implementation has remained elusive so far. Definitely, in most Dirac semimetals, the Dirac point lies deep below the Fermi level, limiting technological exploitation. Here, it is shown that kitkaite (NiTeSe) represents an ideal platform for type-II Dirac fermiology based on spin-resolved angle-resolved photoemission spectroscopy and density functional theory. Precisely, the existence of type-II bulk Dirac fermions is discovered in NiTeSe around the Fermi level and the presence of topological surface states with strong (≈50%) spin polarization. By means of surface-science experiments in near-ambient pressure conditions, chemical inertness towards ambient gases (oxygen and water) is also demonstrated. Correspondingly, NiTeSe-based devices without encapsulation afford long-term efficiency, as demonstrated by the direct implementation of a NiTeSe-based microwave receiver with a room-temperature photocurrent of 2.8 µA at 28 GHz and more than two orders of magnitude linear dynamic range. The findings are essential to bringing to fruition type-II Dirac fermions in photonics, spintronics, and optoelectronics. © 2021 The Authors. Advanced Functional Materials published by Wiley-VCH GmbH.I.V., A.B.S., and L.Z. contributed equally to this work. L.W. acknowledged support from the State Key Program for Basic Research of China (No. 2017YFA0305500, 2018YFA0306204), Shanghai Municipal Science and Technology Major Project (Grant No. 2019SHZDZX01), and the Science and Technology Commission of Shanghai Municipality (21ZR1473800). A.P. thanks CERIC‐ERIC for the access to the NAP‐XPS facility. D.W.B. acknowledged support from the Ministry of Science and Higher Education of the Russian Federation (through the basic part of the government mandate, Project No. FEUZ‐2020‐0060) and Jiangsu Innovative and Entrepreneurial Talents Project. This work has been partly performed in the framework of the nanoscience foundry and fine analysis (NFFA‐MUR Italy Progetti Internazionali) facility. A.B, B.G, and A.A. acknowledge funding from Science and Engineering Research Board (SERB) and Department of Science and Technology (DST), government of India. A.A. thanks the HPC facility at IIT Kanpur for computational resources