Insights from scanning tunneling microscopy experiments into correlated electron systems

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 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.Quantum Matter and Optic

Amplifier for scanning tunneling microscopy at MHz frequencies

Conventional scanning tunneling microscopy (STM) is limited to a bandwidth of circa 1kHz around DC. Here, we develop, build and test a novel amplifier circuit capable of measuring the tunneling current in the MHz regime while simultaneously performing conventional STM measurements. This is achieved with an amplifier circuit including a LC tank with a quality factor exceeding 600 and a home-built, low-noise high electron mobility transistor (HEMT). The amplifier circuit functions while simultaneously scanning with atomic resolution in the tunneling regime, i.e. at junction resistances in the range of giga-ohms, and down towards point contact spectroscopy. To enable high signal-to-noise and meet all technical requirements for the inclusion in a commercial low temperature, ultra-high vacuum STM, we use superconducting cross-wound inductors and choose materials and circuit elements with low heat load. We demonstrate the high performance of the amplifier by spatially mapping the Poissonian noise of tunneling electrons on an atomically clean Au(111) surface. We also show differential conductance spectroscopy measurements at 3MHz, demonstrating superior performance over conventional spectroscopy techniques. Further, our technology could be used to perform impedance matched spin resonance and distinguish Majorana modes from more conventional edge states

Antimicrobial Susceptibilities of Aerobic Isolates from Respiratory Samples of Young New Zealand Horses

3rd Annual IEEE Energy Conversion Congress and Exposition, ECCE 2011, Phoenix, AZ, 17-22 September 2011This paper presents a method of mitigating the transient overshoots of DC-DC converters operating with large load disturbances. The method involves a small auxiliary power circuit with a complementary control scheme that provides a smooth absorption and release of excess energy from and to the main DC-DC converter in the events of large load changes. This control mechanism interactively mitigates the large transient overshoots which would otherwise appear at the converter output. Since the control scheme involves an adjustable-energy-storage feature, the proposed solution is effective for any level of step-load change within a pre-specified range.Department of Electronic and Information EngineeringRefereed conference pape

Beklag over niet vervolgen:Het gaat het Openbaar Ministerie om met art. 12 Sv-zaken?

Een aangifte van een strafbaar feit door een burger leidt vaak niet tot een strafvervolging. De officier van justitie kan beslissen dat de zaak niet aan de rechter wordt voorgelegd, maar wordt geseponeerd. Tegen deze beslissing kan de belanghebbende zich op grond van artikel 12 Wetboek van Strafvordering beklagen bij het gerechtshof. Dit boek bevat een verslag van een onderzoek naar de praktijk van deze beklagprocedure en de kwaliteit van het werk van het Openbaar Ministerie. De centrale vraag in het onderzoek is of het werk van het Openbaar Misisterie in de beklagprocedure beantwoordt aan de kwaliteitseisen die daaraan mogen worden gesteld. Relevante informatie is verkregen door een kwantitatieve analyse van beklagzaken over de jaren 2010-2014, een uitvoerig dossieronderzoek en interviews met functionarissen die betrokken zijn bij een afhandeling van beklagzaken