This thesis presents insights from our study of various correlated electron systems with a scanning tunneling microscope (STM). In ordinary metals, electron-electron interactions exist, but get... Show moreThis thesis presents insights from our study of various correlated electron systems with a scanning tunneling microscope (STM). In ordinary metals, electron-electron interactions exist, but get substantially screened due to the sheer number of electrons. We therefore describe electrons in ordinary metals as a gaseous state of free, or weakly interacting charged particles. This adequately explains their properties, however, this picture does not work for correlated electron materials. The prominent electron-electron interactions present in these materials enable a wide range of exotic electronic phenomena, some of which are presented in this work. In chapter 2, we present STM results measured on an overdoped copper oxide compound and show that the superconducting state that occurs in these materials cannot be described by conventional BCS theory, contrary to what is commonly believed. In chapter 3, we study twisted bilayer graphene devices, and quantify their local twist angle and strain on the nanoscale. In chapter 4, we describe how to build and characterize the hardware needed to do noise spectroscopy measurements in a conventional, low temperature STM setup. Finally, in chapter 5, we present our noise spectroscopy measurements on Sr2IrO4, and explain how random telegraph noise could lead to the observed noise enhancements. Show less
The work in this thesis demonstrates how to obtain an atomic-scale picture of a diverse set of complex surface structures observed using STM, under disparate conditions. Chapters 4−6 each represent... Show moreThe work in this thesis demonstrates how to obtain an atomic-scale picture of a diverse set of complex surface structures observed using STM, under disparate conditions. Chapters 4−6 each represent a different approach to answer the same question: How can we find out what a surface looks like at the atomic scale? By employing appropriate theoretical tools that complement the experimental conditions and measurement techniques, it is possible to compare the results from theory and experiment in an intuitive manner to obtain additional insights. Additionally, Chapter 4 shows that theoretical studies, which do not take experimental conditions into account appropriately, can lead to wrong conclusions. Show less
