Triangular Spin-Orbit-Coupled Lattice with Strong Coulomb Correlations: Sn Atoms on a SiC(0001) Substrate

TL;DR

This study explores a novel 2D lattice of Sn atoms on SiC(0001), revealing strong Coulomb correlations and Mott insulating behavior, serving as a platform for investigating exotic quantum states like spin liquids and topological Mott insulators.

Contribution

First experimental and theoretical investigation of a high-Z atom lattice on SiC(0001), demonstrating Mott insulating behavior and potential for novel quantum states.

Findings

Deeply gapped electronic state (~2 eV) observed experimentally.

Theoretical modeling indicates a Mott insulator driven by Coulomb correlations.

System shows potential susceptibility to antiferromagnetic order.

Abstract

Two-dimensional (2D) atom lattices provide model setups for Coulomb correlations inducing competing ground states, partly with topological character. Hexagonal SiC(0001) is an intriguing wide-gap substrate, spectroscopically separated from the overlayer and hence reduced screening. We report the first study of an artificial high-Z atom lattice on SiC(0001) by Sn adatoms, based on combined experimental realization and theoretical modeling. Density-functional theory of our $\sqrt{3}$-structure model closely reproduces the scanning tunneling microscopy. Instead of metallic behavior, photoemission data show a deeply gapped state (~2 eV gap). Based on our calculations including dynamic mean-field theory, we argue that this reflects a pronounced Mott insulating scenario. We also find indications that the system is susceptible to antiferromagnetic superstructures. Such spin-orbit-coupled correlated heavy atom lattices on SiC(0001) thus form a novel testbed for peculiar quantum states of matter, with potential bearing for spin liquids and topological Mott insulators.