One-dimensional molecular nanostructures interacting with two-dimensional metals

Electrons confined within the 2D layer of metals grown on silicon substrates exhibit exotic properties due to strong correlation effects. Their properties, such as their 2D superconductivity, have been frequently subjected to possible tuning by doping using charge transfer from adsorbed layers. Doping relies on adding electrons or holes to the system and the resulting shift of the Fermi level E_F in the otherwise robust surface electronic structure. This strategy has not been sufficiently controlled in the case of an indium double layer grown on the Si(111) surface. This study provides an alternative approach relying on spatially periodic modification of the surface electronic structure of the 2D metal. Derivatives of diketopyrrolopyrroles (DPP) are used for the growth of perfectly ordered 1D-like molecular superstructures on top of the In double layer, imaged by scanning tunneling microscopy. The integral changes of electronic structure are measured by angle-resolved photoelectron spectroscopy and density functional theory calculations show local modification of the surface states near E_F by the adsorbed molecules. This study demonstrates that the surface electronic states can be controllably patterned, using a proper bonding scheme. It is anticipated that the combination of the original 2D superconductor and the 1D-like patterning will motivate further research.