Mark A. Eriksson, University of Wisconsin-Madison

Valley Physics in Silicon Quantum Wells, Quantum Dots, and Nanomembranes

Silicon quantum wells, point contacts, and quantum dots have an interesting degree of freedom: two low-lying valley states that are degenerate in wide quantum wells but split in narrow wells. I will discuss a microwave spectroscopy of this valley splitting that is an analog of electron spin resonance: electron valley resonance (EVR). The result of the spectroscopy is a valley splitting that is startlingly linear as a function of magnetic field, and a new theory will be presented that helps explain this result. Very recent progress on metal top-gated point contacts and quantum dots has led to highly tunable nanostructures in Si/SiGe. I will present data showing the splitting of all the degeneracies (spin and orbital) in silicon point contacts, and I will show evidence of a Kondo-like zero-bias anomaly in silicon quantum dots. In addition to patterned nanostructures, silicon can also form spectacular membranes, one hundred nanometers thick and a centimeter across. Such nanomembranes can be bent, strained, and rolled into tubes. These properties offer the potential to use strain in a dislocation-free system, potentially leading to new ways to create quantum dots without the epitaxial growth complexities that in the past have been required. X-ray scattering results and low temperature electronic transport measurements will be presented, demonstrating dramatic changes in transport properties before and after the release and subsequent redeposition of these flexible, yet single crystal membranes.