Integrated Calendar

2-D electron gases residing on the crystallographic surfaces of atomically flat and ultra-clean metal surfaces have been studied in detail by measurements of the energy bands in momentum as well as in real space. For instance, on various Cu and Au surfaces, the energy vs. wavevector relationship, including the effects of (Rashba) spin-orbit interaction, have been measured by ARPES. On the other hand, the local density of states on unperturbed facets and on surface positions close to atomic defects has been studied in detail by scanning tunnelling microscopy and spectroscopy.
More recently, the surface state electrons have been moulded into artificial molecules and 2-D lattices created by manipulation of ad-atoms and CO molecules on metallic surfaces in an STM. Here, manipulation in an STM is used to position ad-atoms or CO molecules on the metal surface in order to form arrays or repulsive scatters that force the surface electrons into certain patterns. In this way, arrays of artificial atomic sites can be engineered, as well as the quantum coupling between these sites in a given lattice. In such a way, artificial lattices form a nearly ideal platform to study the relationship between the lattice geometry and electronic band structure of 2-D systems. This includes the study of Dirac bands and topological electronic phases emerging from the lattice geometry and the nature of the scatters1-4. I will discuss the progress obtained in this field in recent years by us and other groups. I will also show the relevance of this work for real materials with a Dirac or topological band structure5,6.