Quasi One Dimensional Dirac Electrons on the Surface of Ru$_2$Sn$_3$

TL;DR

This study reveals that Ru$_2$Sn$_3$ hosts highly anisotropic, quasi-one-dimensional Dirac surface states resulting from a d-p band inversion, differing from typical 3D topological insulators with isotropic Dirac cones.

Contribution

It reports the discovery of anisotropic, quasi-1D Dirac surface states in Ru$_2$Sn$_3$, a new 3D topological insulator with a unique d-p band inversion mechanism.

Findings

Surface states are highly anisotropic and quasi-1D.

Surface states originate from d-p band inversion.

Surface exhibits a single 2D Dirac cone.

Abstract

We present an ARPES study of the surface states of Ru$_2$Sn$_3$, a new type of a strong 3D topological insulator (TI). In contrast to currently known 3D TIs, which display two-dimensional Dirac cones with linear isotropic dispersions crossing through one point in the surface Brillouin Zone (SBZ), the surface states on Ru$_2$Sn$_3$ are highly anisotropic, displaying an almost flat dispersion along certain high-symmetry directions. This results in quasi-one dimensional (1D) Dirac electronic states throughout the SBZ that we argue are inherited from features in the bulk electronic structure of Ru$_2$Sn$_3$, where the bulk conduction bands are highly anisotropic. Unlike previous experimentally characterized TIs, the topological surface states of Ru$_2$Sn$_3$ are the result of a d-p band inversion rather than an s-p band inversion. The observed surface states are the topological equivalent to a single 2D Dirac cone at the surface Brillouin zone