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DDC: 540 × Subject: electronic structure ×

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    Signatures of Sixfold Degenerate Exotic Fermions in a Superconducting Metal PdSb2
    (Weinheim : Wiley-VCH, 2020) Kumar, Nitesh; Yao, Mengyu; Nayak, Jayita; Vergniory, Maia G.; Bannies, Jörn; Wang, Zhijun; Schröter, Niels B.M.; Strocov, Vladimir N.; Müchler, Lukas; Shi, Wujun; Rienks, Emile D.L.; Mañes, J.L.; Shekhar, Chandra; Parkin, Stuart S.P.; Fink, Jörg; Fecher, Gerhard H.; Sun, Yan; Bernevig, B. Andrei; Felser, Claudia
    Multifold degenerate points in the electronic structure of metals lead to exotic behaviors. These range from twofold and fourfold degenerate Weyl and Dirac points, respectively, to sixfold and eightfold degenerate points that are predicted to give rise, under modest magnetic fields or strain, to topological semimetallic behaviors. The present study shows that the nonsymmorphic compound PdSb2 hosts six-component fermions or sextuplets. Using angle-resolved photoemission spectroscopy, crossing points formed by three twofold degenerate parabolic bands are directly observed at the corner of the Brillouin zone. The group theory analysis proves that under weak spin–orbit interaction, a band inversion occurs. © 2020 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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    Electronic structure and morphology of dark oxides on zinc generated by electrochemical treatment
    (London [u.a.] : Royal Society of Chemistry, 2013) Chen, Y.; Schneider, P.; Liu, B.-J.; Borodin, S.; Ren, B.; Erbe, A.
    Oxides formed by electrochemical treatment of metals frequently have properties and structures very different from the respective bulk oxides. Here, electronic structure and chemical composition were investigated for the oxide formed on polycrystalline zinc after electrochemical oxidation, and after subsequent reduction, in a Na2CO3 electrolyte. Photoluminescence and spectroscopic ellipsometry show the presence of states deep in the ZnO band gap in the oxidized sample, which consists of a highly disordered oxide. These states determine the absorption of light in the visible spectral range. After reduction, the characteristics of the ZnO electronic structure have disappeared, leaving a defect-dominated material with a band gap of ∼1.8 eV. Complementary detailed analysis of the morphology of the resulting surfaces shows hexagon-shaped metallic Zn-"nanoplates" to be formed in the reduction step. The optical appearance of the surfaces is dark, because of their efficient extinction of light over a large part of the visible spectrum. The optical appearance is a result of changed surface morphology and electronic structure of the oxide film. Such materials may possess interesting applications in photocatalysis or photoelectrochemistry.