SiC(0001): a surface Mott-Hubbard insulator

TL;DR

This study uses ab-initio calculations to show that the Si-terminated SiC(0001) surface is a Mott-Hubbard insulator due to Coulomb interactions, with a predicted gap close to experimental observations.

Contribution

It demonstrates that Coulomb effects induce a Mott-Hubbard insulating state on SiC(0001), providing a theoretical explanation for experimental surface properties.

Findings

Coulomb interactions open a 1.5 eV gap, matching experimental data.

Surface exhibits a paramagnetic Mott state at typical temperatures.

Surface core level splitting explained by on-site exchange effects.

Abstract

We present ab-initio electronic structure calculations for the Si-terminated SiC(0001)$\sqrt{3}\times\sqrt{3}$ surface. While local density approximation (LDA) calculations predict a metallic ground state with a half-filled narrow band, Coulomb effects, included by the spin-polarized LDA+U method, result in a magnetic (Mott-Hubbard) insulator with a gap of 1.5 eV, comparable with the experimental value of 2.0 eV. The calculated value of the inter-site exchange parameter, J=30K, leads to the prediction of a paramagnetic Mott state, except at very low temperatures. The observed Si 2p surface core level doublet can naturally be explained as an on-site exchange splitting.