We have performed the semilocal and hybrid density-functional theory (DFT) studies of the Sn/Ge(111) surface to identify the origin of the observed insulating 3×3 phase below ∼30 K. Contrasting with the semilocal DFT calculation predicting a metallic 3×3 ground state, the hybrid DFT calculation including van der Waals interactions shows that the insulating ferrimagnetic structure with 3×3 structural symmetry is energetically favored over the metallic 3×3 structure. It is revealed that the correction of self-interaction error with a hybrid exchange-correlation functional gives rise to a band-gap opening induced by a ferrimagnetic order. The results manifest that the observed insulating phase is attributed to the Slater mechanism via itinerant magnetic order rather than the hitherto accepted Mott-Hubbard mechanism via electron correlations.
@article{arxiv.1310.1782,
title = {Ferrimagnetic Slater Insulator Phase of the Sn/Ge(111) Surface},
author = {Jun-Ho Lee and Hyun-Jung Kim and Jun-Hyung Cho},
journal= {arXiv preprint arXiv:1310.1782},
year = {2013}
}