Structural and electrical characterization of the monolayer Kondo-lattice compound CePt6/Pt(111)

We report the growth process, structure, and electronic states of 1 unit layer (u.l.) of a Ce-Pt intermetallic compound on Pt(111) using scanning tunneling microscopy/spectroscopy (STM/STS) and low-energy electron diffraction. An ordered $(2\ifmmode\times\else\texttimes\fi{}2)$ structure was observed in the form of films or nanoislands depending on Ce dose by annealing at around 700 K. A structural model constructed from atomically resolved STM images and quasiparticle interference (QPI) patterns indicates the formation of a new surface compound 1 u.l. ${\mathrm{CePt}}_{6}$ on Pt(111) terminated by a Pt layer. A lateral lattice constant of the 1 u.l. ${\mathrm{CePt}}_{6}$ on Pt(111) is expanded from the value of a bulk ${\mathrm{CePt}}_{5}$ crystal to match the Pt(111) substrate. By measuring $dI/dV$ spectra and QPI, we observed an onset energy of the surface state found on Pt(111) above Fermi energy (${E}_{F}$) shifts below ${E}_{F}$ on the Pt layer of the 1 u.l. ${\mathrm{CePt}}_{6}$ due to charge transfer from the underneath ${\mathrm{CePt}}_{2}$ layer. We discuss a possible two-dimensional coherent Kondo effect with the observed spectra on the 1 u.l. ${\mathrm{CePt}}_{6}$.