Nano-scale electronic structure of strongly correlated electron systems

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 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.Quantum Matter and Optic

Direct evidence for Cooper pairing without a spectral gap in a disordered superconductor above Tc

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, 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.Quantum Matter and Optic

Complex pharmaceutical care intervention in pulmonary care Part B. Patient opinion and process survey

Objective: The IPMP study (Interventions on the principle of Pulmonary Medication Profiles) investigates and describes the results of complex pharmaceutical care interventions provided to selected pulmonary patients to improve their drug use. This paper describes the patients' opinions about the care provided and the results of the intervention. Method: Questionnaires investigating patients' opinions about provided pharmaceutical care were sent to 185 patients participating in the IPMP study after the intervention by their pharmacists had been finished. One year after the start of the intervention, patients were invited to a final consultation by their pharmacists to evaluate their drug use and their symptoms (n = 138). At this point in time pharmacists investigated the knowledge of the patients about the medication and their inhaler technique again. Main outcome measure: The influence of the intervention on patients' symptoms. Change in drug-related problems, knowledge and skills concerning pulmonary medication after intervention. Satisfaction of the patients with the provided pharmaceutical care. Results: In total 141 out of 185 patients completed the questionnaire. Patients were satisfied with the intervention by their pharmacists and considered it important. The majority (67%) reported that they had learned more about their medication or the inhaler technique, resulting in significantly improved coping behaviour with their pulmonary medication compared with patients who valued the intervention as a nice conversation with their pharmacist only. Patients with improved ability to cope reported statistically significantly fewer symptoms compared with patients reporting no change in behaviour (chi-square test, P <0.05). In the final consultation of 138 patients, pharmacists observed increased knowledge and skills and decreased drug-related problems. The patients concerned were pleased with the change in treatment and were more satisfied with their current medication as compared with their earlier reports. Conclusion: Patients can be influenced effectively by the tailored intervention of pharmacists resulting in improved ability to cope with pulmonary medication and in fewer reported adverse effects and symptoms. Patients attributed these results to the intervention of the pharmacists

Puddle formation and persistent gaps across the non-mean-field breakdown of superconductivity in overdoped (Pb,Bi)₂Sr₂CuO_6+<i>δ</i>

The cuprate high-temperature superconductors exhibit many unexplained electronic phases, but the superconductivity at high doping is often believed to be governed by conventional mean-field Bardeen–Cooper–Schrieffer theory. However, it was shown that the superfluid density vanishes when the transition temperature goes to zero, in contradiction to expectations from Bardeen–Cooper–Schrieffer theory. Our scanning tunnelling spectroscopy measurements in the overdoped regime of the (Pb,Bi)2Sr2CuO6+δ high-temperature superconductor show that this is due to the emergence of nanoscale superconducting puddles in a metallic matrix. Our measurements further reveal that this puddling is driven by gap filling instead of gap closing. The important implication is that it is not a diminishing pairing interaction that causes the breakdown of superconductivity. Unexpectedly, the measured gap-to-filling correlation also reveals that pair breaking by disorder does not play a dominant role and that the mechanism of superconductivity in overdoped cuprate superconductors is qualitatively different from conventional mean-field theory.</p