2019/07/31 by Niels B. M. Schröter, Samuel Stolz, Kaustuv Manna +13 · 1 citation
Physics and Astronomy · #cond-mat.mes-hall
paper · pdf · doi:10.1126/science.aaz3480
published as Science 369, 179-183, aaz3480 (2020) · Accepted manuscript
arxiv created 2020/07/09 · arxiv updated 2020/07/10
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, which sets an upper limit to the magnitude of many topological phenomena in these materials. Here we show that the chiral crystal 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.