Topological Dirac states beyond $\pi$ orbitals for silicene on SiC(0001) surface

TL;DR

This study predicts the existence of topologically nontrivial Dirac states originating from $p_{x,y}$ orbitals in silicene on SiC(0001), which remain stable despite strong substrate interactions, opening new avenues for nanoelectronic applications.

Contribution

It reveals the presence of $p_{x,y}$-orbital Dirac states in silicene on SiC(0001) that survive substrate interactions and exhibit nontrivial topological properties, a novel finding beyond conventional $p_z$-orbital states.

Findings

Dirac states from $p_{x,y}$ orbitals are stable on SiC(0001)

The system exhibits a band gap of 1.3 meV due to exchange and spin-orbit coupling

Berry curvature indicates a topological phase with Chern number $C=2$

Abstract

The discovery of intriguing properties related to the Dirac states in graphene has spurred huge interest in exploring its two-dimensional group-IV counterparts, such as silicene, germanene, and stanene. However, these materials have to be obtained via synthesizing on substrates with strong interfacial interactions, which usually destroy their intrinsic $\pi$($p_z$)-orbital Dirac states. Here we report a theoretical study on the existence of Dirac states arising from the $p_{x,y}$ orbitals instead of $p_z$ orbitals in silicene on 4H-SiC(0001), which survive in spite of the strong interfacial interactions. We also show that the exchange field together with the spin-orbital coupling give rise to a detectable band gap of 1.3 meV. Berry curvature calculations demonstrate the nontrivial topological nature of such Dirac states with a Chern number $C = 2$, presenting the potential of realizing quantum anomalous Hall effect for silicene on SiC(0001). Finally, we construct a minimal effective model to capture the low-energy physics of this system. This finding is expected to be also applicable to germanene and stanene, and imply great application potentials in nanoelectronics.