α -Sn phase on Si(111): Spin texture of a two-dimensional Mott state

The $\ensuremath{\alpha}$-Sn reconstruction on Si(111) is a prototype system for a two-dimensional Mott phase. In this study we performed spin-resolved photoemission experiments and analyzed in detail the spin structure of this electronically correlated surface state. The analysis of the spin-integrated bands as well as the spin texture of the surface states along different crystallographic directions provide clear evidence for the formation of collinear antiferromagnetic $(2\sqrt{3}\ifmmode\times\else\texttimes\fi{}\sqrt{3})$ domains, while the Sn reconstruction reveals a $(\sqrt{3}\ifmmode\times\else\texttimes\fi{}\sqrt{3})$ symmetry. The Rashba splitting of the highest occupied Mott state was found to be $\mathrm{\ensuremath{\Delta}}k=0.05\phantom{\rule{0.16em}{0ex}}{\AA{}}^{\ensuremath{-}1}$, i.e., the $\ensuremath{\alpha}$-Sn phase should be termed a weakly spin-orbit coupled Mott system.