In condensed matter systems electron-electron interactions, negligible in everyday metals, can dramatically alter the electronic behavior of the system. Examples of such altered behavior include... Show moreIn condensed matter systems electron-electron interactions, negligible in everyday metals, can dramatically alter the electronic behavior of the system. Examples of such altered behavior include high-temperature superconductivity and modulation of the electron density. A common feature of this correlation driven behavior is the tendency of the spatial electronic structure to vary on the nanometer scale. In this thesis we explore the nanoscale variation of the electronic structure of various correlated electron systems. We use the wave-like oscillations in the electron density of states to probe fundamental properties of the system providing insights into when various experimental probes disagree with each other. Turning our attention to high-temperature superconductors we find that close to the transition between superconductor and metal a granular superconductor emerges, small nanoscale patches of superconductivity interlaces with a metallic matrix. A careful examination of the wave-like oscillations hints at the presence of spatial ordering of the electrons. Finally we study how the presence of strong interactions can alter the way electrons flow through a material such that concepts usually reserved for everyday fluids become relevant. Show less
The idea that preformed Cooper pairs could exist in a superconductor at temperatures higher than its zero-resistance critical temperature (T-c) has been explored for unconventional, interfacial,... Show moreThe idea that preformed Cooper pairs could exist in a superconductor at temperatures higher than its zero-resistance critical temperature (T-c) has been explored for unconventional, interfacial, and disordered superconductors, but direct experimental evidence is lacking. We used scanning tunneling noise spectroscopy to show that preformed Cooper pairs exist up to temperatures much higher than T-c in the disordered superconductor titanium nitride by observing an enhancement in the shot noise that is equivalent to a change of the effective charge from one to two electron charges. We further show that the spectroscopic gap fills up rather than closes with increasing temperature. Our results demonstrate the existence of a state above T-c that, much like an ordinary metal, has no (pseudo)gap but carries charge through paired electrons. Show less
Discrepancies in the low-energy quasiparticle dispersion extracted from angle-resolved photoemission, scanning tunneling spectroscopy, and quantum oscillation data are common and have long haunted... Show moreDiscrepancies in the low-energy quasiparticle dispersion extracted from angle-resolved photoemission, scanning tunneling spectroscopy, and quantum oscillation data are common and have long haunted the field of quantum matter physics. Here, we directly test the consistency of results from these three techniques by comparing data from the correlated metal Sr2RhO4. Using established schemes for the interpretation of the experimental data, we find good agreement for the Fermi surface topography and carrier effective masses. Hence, the apparent absence of such an agreement in other quantum materials, including the cuprates, suggests that the electronic states in these materials are of different, non-Fermi liquid-like nature. Finally, we discuss the potential and challenges in extracting carrier lifetimes from photoemission and quasiparticle interference data. Show less
