Abstract
This aim of this project was to investigate electronic behaviour in artificial atoms, molecules and lattices. To this end, we made use of a scanning tunnelling microscope (STM) to create, image, and characterise these structures. We used a copper (111) surface cooled to 4.5 K, with carbon monoxide adsorbed onto
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it. The carbon monoxide molecules were manipulated one-by-one with the tip of the STM to sculpt an electronic potential landscape at will. In this way, the surface electrons that exist on the copper surface become trapped within the imposed patterns. A single confined pool of electrons, known as a quantum corral, exhibits atomic behaviour. During this project, we coupled quantum corrals to form artificial molecules. Furthermore, we created entire artificial lattices with the same technique; one that exhibited topological edge modes, and one that could model two-particle interactions. Aside from this, we developed a neural-network based STM image recognition algorithm with the goal of improving the efficiency of STM measurements.
A short description of each chapter of the thesis is as follows:
Chapter 1 contains a short introduction to the thesis.
In chapter 2, a more in-depth background and overview on electronic artificial lattices is given, and most lattices that have been created with the CO/Cu(111) platform are reviewed. We also give an outlook on how such research could find applications in technology.
Chapter 3 presents the goal of making STM experiments as a whole more efficient, therefore reducing the time needed to fabricate artificial lattices atom-by-atom. To this end, we developed an algorithm that could distinguish the state of the STM tip using neural network-based image recognition.
The basic elements of the CO/Cu(111) platform - quantum corrals - and their coupling into artificial molecules, were investigated in chapter 4. This allowed us to gain a sense of the range of parameters that can be tuned in artificial lattices of the same sort.
In the remaining chapters, we engineered and performed measurements on two artificial lattices with the CO/Cu(111) platform that have theoretically been predicted to have interesting properties, but in nature do not exist:
Chapter 5 reports the results of a study into an artificial crystalline topological insulator (TCI). Specifically, we exploit the atomic scale precision to study the influence of edge geometry on the emergence of topological states in TCIs.
Finally, chapter 6 describes a study into how two-body interactions in 1D can be investigated using a non-interacting 2D artificial lattice.
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