Unique Dirac and triple point fermiology in simple transition metals and their binary alloys

Abstract

Noble-metal surfaces (Au, Ag, Cu, etc.) have been extensively studied for Shockley-type surface states (SSs). Very recently, some of these Shockley SSs have been understood from the topological consideration, with the knowledge of global properties of electronic structure. In this paper, we show the existence of Dirac-like excitations in the elemental noble-metal Ru, Re, and Os based on symmetry analysis and first-principles calculations. The unique SS-driven Fermi arcs have been investigated in detail for these metals. Our calculated SSs and Fermi arcs are consistent with the previous transport and photoemission results. We attribute this Dirac excitation-mediated Fermi arc topology as the possible reason for several existing transport anomalies, such as large nonsaturating magnetoresistance, the anomalous Nernst electromotive force and its giant oscillations, magnetic breakdown, etc. We further show that the Dirac-like excitations in these elemental metals can further be tuned to three component Fermionic excitations, using a symmetry-allowed alloy mechanism. © 2020 American Physical Society.