Forging Topological Insulators on the Copper Surface State

Abstract

Artificial electronic lattices are quickly coming to the forefront of nanotechnological research. One form of particular interest for its low- resistance conductive properties is the topological insulator. In this thesis we consider the creation of a topological insulator in the shape of the Kekule lattice. Using scanning tunnelling microscopy (STM) we were able to manipulate singular carbon-monoxide (CO) atoms on a copper (111) surface to confine the existing copper surface state into artificial atoms shaped into the Kekule lattice. The Kekule lattice was built in multiple variations to test for the existence and qualities of topological edge states based on the ratio of the nearest-neighbour hopping parameter T0/T1 and the influence of lattice geometry on the topological edge states. The existence of the topological edge state was confirmed using differential conductance mapping and spectroscopy and tested for robustness by introducing defects into the lattice. The lack of a topological edge state for the lattices designed to have none was confirmed using differential conductance mapping and spectroscopy. These practical results align strongly with theory and simulations done using tight binding (TB) and muffin tin (MT) calculation methods. With these results we hope to provide a basis for the realisation of artificial topological insulators and other conductive artificial systems.