We report an investigation on the properties of 0.33 ML of Sn on Ge(111) at temperatures down to 5 K. Low-energy electron diffraction and scanning tunneling microscopy show that the (3x3) phase formed at 200 K, reverts to a new (root-3xroot-3)R30 phase below 30 K. The vertical distortion characteristic of the (3x3) phase is lost across the phase transition. Angle-resolved photoemission experiments show that concomitantly with the structural phase transition, a metal-insulator phase transition takes place. In agreement with theoretical predictions, the (root-3xroot-3)R30 ground state is interpreted as the experimental realization of a Mott insulator for a narrow half-filled band in a two-dimensional triangular lattice.
@article{arxiv.cond-mat/0601029,
title = {Observation of a Mott insulating ground state for Sn/Ge(111) at low temperature},
author = {R. Cortes and A. Tejeda and J. Lobo and C. Didiot and B. Kierren and D. Malterre and E. G. Michel and A. Mascaraque},
journal= {arXiv preprint arXiv:cond-mat/0601029},
year = {2009}
}