Material realization of spinless, covalent-type Dirac semimetals in three dimensions

TL;DR

This paper reports the discovery of covalent-type 3D Dirac semimetals $R_8$Co$X_3$, which exhibit high carrier mobility and offer a new platform for studying Dirac electrons in three dimensions.

Contribution

It introduces a new class of covalent 3D Dirac semimetals stabilized by covalent bonding, expanding the material platform for topological semimetals.

Findings

Carrier mobility reaches 3,000 cm^2/Vs in polycrystalline samples.

Mobility increases with inverse Fermi energy, indicating Dirac electron contribution.

Provides a chemically tunable platform for 3D Dirac electron exploration.

Abstract

Realization of a three-dimensional (3D) analogue of graphene has been a central challenge in topological materials science. Graphene is stabilized by covalent bonding unlike conventional spin-orbit type 3D Dirac semimetals (DSMs). In this study, we demonstrate the material realization of covalent-type 3D DSMs $R_8$Co$X_3$ stabilized by covalent bonding. We observe that the carrier mobility $\mu$ of Dirac fermions reaches 3,000$\,\mathrm{cm^2/Vs}$ even in polycrystalline samples, and $\mu$ increases with the inverse of the Fermi energy, evidencing significant contributions to charge transport from Dirac electrons. $R_8$Co$X_3$ provides a material platform for exploration of Dirac electrons in three dimensions with wide chemical tunability.