Observation and control of maximal Chern numbers in a chiral topological semimetal

DOI: 10.1126/science.aaz3480

Authors: Niels B. M. Schroeter (Swiss Light Source) , Samuel Stolz (EMPA, Swiss Federal Laboratories for Materials Science and Technology; EPFL) , Kaustuv Manna (Max Planck Institute for Chemical Physics of Solids) , Fernando De Juan (Donostia International Physics Center; IKERBASQUE, Basque Foundation for Science) , Maia G. Vergniory (Donostia International Physics Center; IKERBASQUE, Basque Foundation for Science) , Jonas A. Krieger (Swiss Light Source; Paul Scherrer Institute; ETH Zurich) , Ding Pei (University of Oxford) , Thorsten Schmitt (Swiss Light Source) , Pavel Dudin (Diamond Light Source) , Timur K. Kim (Diamond Light Source) , Cephise Cacho (Diamond Light Source) , Barry Bradlyn (University of Illinois at Urbana-Champaign) , Horst Borrmann (Max Planck Institute for Chemical Physics of Solids) , Marcus Schmidt (Max Planck Institute for Chemical Physics of Solids) , Roland Widmer (EMPA, Swiss Federal Laboratories for Materials Science and Technology) , Vladimir N. Strocov (Swiss Light Source) , Claudia Felser (Max Planck Institute for Chemical Physics of Solids)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Science , VOL 369 , PAGES 179 - 183

State: Published (Approved)
Published: July 2020
Diamond Proposal Number(s): 24703 , 20617

Abstract: Topological semimetals feature protected nodal band degeneracies characterized by a topological invariant known as the Chern number (C). Nodal band crossings with linear dispersion are expected to have at most |C|=4 | C | = 4 , which sets an upper limit to the magnitude of many topological phenomena in these materials. Here, we show that the chiral crystal palladium gallium (PdGa) displays multifold band crossings, which are connected by exactly four surface Fermi arcs, thus proving that they carry the maximal Chern number magnitude of 4. By comparing two enantiomers, we observe a reversal of their Fermi-arc velocities, which demonstrates that the handedness of chiral crystals can be used to control the sign of their Chern numbers.

Journal Keywords: Topology; Chern number; ARPES; Chirality; Fermi-arcs; Surface-state; Handedness; New fermions; Rarita-Schwinger; Weyl-fermion

Subject Areas: Physics, Materials


Instruments: I05-ARPES

Added On: 14/07/2020 14:15

Documents:
179.full.pdf

Discipline Tags:

Materials Science Quantum Materials Physics Hard condensed matter - structures

Technical Tags:

Spectroscopy Angle Resolved Photoemission Spectroscopy (ARPES)