Mott Insulating Ground State on a Triangular Surface Lattice

Abstract

Momentum-resolved direct and inverse photoemission spectra of the $\mathrm{K}/\mathrm{Si}\left(111\right)\ensuremath{-}(\sqrt{3}\ifmmode\times\else\texttimes\fi{}\sqrt{3})R30\ifmmode^\circ\else\textdegree\fi{}\ensuremath{-}\mathrm{B}$ interface reveals the presence of strongly localized surface states. The K overlayer remains nonmetallic up to the saturation coverage. This system most likely presents the first experimental realization of a frustrated spin $1/2$ Heisenberg antiferromagnet on a two-dimensional triangular lattice.