Mott- versus Slater-type Insulating Nature of Two-Dimensional Sn Atom Lattice on SiC(0001)

TL;DR

This study uses density-functional theory to analyze the insulating nature of a 2D Sn atom lattice on SiC(0001), revealing it as a Slater-type insulator driven by long-range magnetic interactions, contrasting previous Mott-insulator assumptions.

Contribution

The paper demonstrates that the Sn/SiC(0001) system is better described as a Slater insulator influenced by long-range magnetism, challenging earlier Mott-insulator models.

Findings

Band gap and density of states match photoemission data

Hybridization stabilizes antiferromagnetic order

Long-range interactions are crucial for accurate description

Abstract

Semiconductor surfaces with narrow surface bands provide unique playgrounds to search for Mott-insulating state. Recently, a combined experimental and theoretical study [Phys. Rev. Lett. 114, 247602 (2015)] of the two-dimensional (2D) Sn atom lattice on a wide-gap SiC(0001) substrate proposed a Mott-type insulator driven by strong on-site Coulomb repulsion U. Our systematic density-functional theory (DFT) study with local, semilocal, and hybrid exchange-correlation functionals shows that the Sn dangling-bond state largely hybridizes with the substrate Si 3p and C 2p states to split into three surface bands due to the crystal field. Such a hybridization gives rise to the stabilization of the antiferromagnetic order via superexchange interactions. The band gap and the density of states predicted by the hybrid DFT calculation agree well with photoemission data. Our findings not only suggest that the Sn/SiC(0001) system can be represented as a Slater-type insulator driven by long-range magnetism, but also have an implication that taking into account long-range interactions beyond the on-site interaction would be of importance for properly describing the insulating nature of Sn/SiC(0001).