Signatures of Sixfold Degenerate Exotic Fermions in a Superconducting Metal PdSb2

Nitesh Kumar; Mengyu Yao; Jayita Nayak; Maia G Vergniory; Jörn Bannies; Zhijun Wang; Niels B M Schröter; Vladimir N Strocov; Lukas Müchler; Wujun Shi; Emile D L Rienks; J L Mañes; Chandra Shekhar; Stuart S P Parkin; Jörg Fink; Gerhard H Fecher; Yan Sun; B Andrei Bernevig; Claudia Felser

doi:10.1002/adma.201906046

Signatures of Sixfold Degenerate Exotic Fermions in a Superconducting Metal PdSb₂

Adv Mater. 2020 Mar;32(11):e1906046. doi: 10.1002/adma.201906046. Epub 2020 Feb 9.

Authors

Nitesh Kumar¹, Mengyu Yao¹, Jayita Nayak¹, Maia G Vergniory^{2

3}, Jörn Bannies¹, Zhijun Wang⁴, Niels B M Schröter⁵, Vladimir N Strocov⁵, Lukas Müchler^{1

6}, Wujun Shi¹, Emile D L Rienks^{7

8}, J L Mañes⁹, Chandra Shekhar¹, Stuart S P Parkin¹⁰, Jörg Fink^{1

7

8}, Gerhard H Fecher¹, Yan Sun¹, B Andrei Bernevig⁴, Claudia Felser¹

Affiliations

¹ Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Str. 40, 01187, Dresden, Germany.
² Donostian International Physics Center, Paseo Manuel de Lardizabal 4, 20018, San Sebastian, Spain.
³ KERBASQUE, Basque Foundation for Science, Maria Diaz de Haro 3, 48013, Bilbao, Spain.
⁴ Department of Physics, Princeton University, Princeton, NJ, 08544, USA.
⁵ Paul Scherrer Institute, 5232, Villigen, PSI, Switzerland.
⁶ Center for Computational Quantum Physics, The Flatiron Institute, New York, NY, 10010, USA.
⁷ Leibniz Institut für Festkörper und Werkstoffforschung IFW Dresden, Helmholtzstrasse 20, 01171, Dresden, Germany.
⁸ Institute of Solid State Physics, Dresden University of Technology, Zellescher Weg 16, 01062, Dresden, Germany.
⁹ Condensed Matter Physics Department, Faculty of Science and Technology, University of the Basque Country UPV/EHU, Apdo. 644, 48080, Bilbao, Spain.
¹⁰ Max Planck Institute of Microstructure Physics, 06120, Halle, Germany.

PMID: 32037624
DOI: 10.1002/adma.201906046

Abstract

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.

Keywords: angle-resolved photoemission spectroscopy; electronic structure; first principle calculations; multifold degenerate points; topological materials.

Grants and funding

742068/ERC