In the exotic realm of topological materials, a team of scientists proposed a link between the chirality of physical structures and the chirality of electronic behavior, and has now confirmed the relationship in crystals. Using spectroscopy at the Advanced Light Source (ALS), the group was able to determine the electronic properties of these new topological conductors. The discovery holds promise for new materials, electronics, optics, and quantum computing.
Structures of opposite chirality are mirror images that cannot be superimposed on each other, like a pair of gloves or a left-handed spiral and its right-handed counterpart. Researchers hypothesized that the chiral arrangement of atoms in cobalt-silicon and rhodium-silicon crystals would give rise to chiral electronic behavior. After sample preparation at the Molecular Foundry, angle-resolved photoemission spectroscopy (ARPES) at ALS Beamlines 10.0.1 and 4.0.3 produced the clear signature of a topological chiral crystal: electronic structures, known as Fermi arcs, that were spiral. The Fermi arcs are very prominent in these topological chiral crystals leading to very robust quantum properties.
Shining infrared light on the silicon-based crystals produces an electrical current of fixed strength that does not vary even when defects appear in the sample, a hallmark of chiral topological materials. The conductivity of these silicon-based chiral crystals suggests that many other materials made of chiral crystals can be harnessed for novel electronic use. Many new types of applications could be possible by combining topological chiral crystals with magnets or superconductors.
D.S. Sanchez, I. Belopolski, T.A. Cochran, X. Xu, J.-X. Yin, G. Chang, W. Xie, K. Manna, V. Süß, C.-Y. Huang, N. Alidoust, D. Multer, S.S. Zhang, N. Shumiya, X. Wang, G.-Q. Wang, T.-R. Chang, C. Felser, S.-Y. Xu, S. Jia, H. Lin, and M.Z. Hasan, “Topological chiral crystals with helicoid-arc quantum states,” Nature 567, 500 (2019), doi:10.1038/s41586-019-1037-2.
Adapted from the Berkeley Lab press release, “The Best Topological Conductor Yet: Spiraling Crystal Is the Key to Exotic Discovery.”
Read more about the discovery of Weyl fermions, central to the function of topological conductors.