Ground States Of The Two Dimensional Electron System At Half Filling Under Hydrostatic Pressure

Ground States of the Two-Dimensional Electron System at Half-Filling under Hydrostatic Pressure

This thesis presents the discovery of a surprising phase transition between a topological and a broken symmetry phase. Phase transitions between broken symmetry phases involve a change in symmetry and those between topological phases require a change in topological order; in rare cases, however, transitions may occur between these two broad classes of phases in which the vanishing of the topological order is accompanied by the emergence of a broken symmetry. This thesis describes observations of such a special phase transition in the two-dimensional electron gas confined in the GaAs/AlGaAs structures. When tuned by hydrostatic pressure, the ν = 5/2 and ν = 7/2 fractional quantum Hall states, believed to be prototypical non-Abelian topological phases of the Pfaffian universality class, give way to an electronic nematic phase. Remarkably, the fractional quantum Hall states involved are due to pairing of emergent particles called composite fermions. The findings reported here, therefore, provide an interesting example of competition of pairing and nematicity. This thesis provides an introduction to quantum Hall physics of the two-dimensional electron gas, contains details of the high pressure experiments, and offers a discussion of the ramifications and of the origins of the newly reported phase transition.

Ground States of the Two-Dimensional Electron System at Half-Filling Under Hydrostatic Pressure

Functional Materials

The world is currently facing the urgent and demanding challenges of saving and utilizing energy as efficiently as possible. Materials science, where chemistry meets physics, has garnered a great deal of attention because of its versatile techniques for designing and producing new, desired materials enabling energy storage and conversion. This book is a comprehensive survey of the research on such materials. Unlike a monograph or a review book, it covers a wide variety of compounds, details diverse study methodologies, and spans different scientific fields. It contains cutting-edge research in chemistry and physics from the interdisciplinary team of Ehime University (Japan), the members of which are currently broadening the horizon of materials sciences through their own ideas, tailored equipment, and state-of-the-art techniques. Edited by Toshio Naito, a prominent materials scientist, this book will appeal to anyone interested in solid-state chemistry, organic and inorganic semiconductors, low-temperature physics, or the development of functional materials, including advanced undergraduate- and graduate-level students of solid-state properties and researchers in metal-complex science, materials science, chemistry, and physics, especially those with an interest in (semi)conducting and/or magnetic materials for energy storage and conversion.