Spectroscopic fingerprints of a surface Mott–Hubbard insulator: the case of SiC(0001)

We discuss the spectroscopic fingerprints that a surface Mott–Hubbard insulator should show at the intra-atomic level. The test case considered is that of the Si-terminated SiC(0001)3×3 surface, which is known experimentally to be insulating. We argue that, owing to the Mott–Hubbard phenomenon, spin unpaired electrons in the Si adatom dangling bonds are expected to give rise to an Si 2p core level spectrum with a characteristic three-peaked structure, as seen experimentally. This structure results from the joint effect of intra-atomic exchange, spatial anisotropy, and spin–orbit coupling. Auger intensities are also discussed.