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

1. Front Matter

   Pages i-xiii

   PDF

2. The Quantum Hall Effect

   • Katherine A. Schreiber

   Pages 1-24

3. The Quantum Hall Nematic Phase

   • Katherine A. Schreiber

   Pages 25-36

4. Low Temperature Measurement Techniques

   • Katherine A. Schreiber

   Pages 37-42

5. The Quantum Hall Effect and Hydrostatic Pressure

   • Katherine A. Schreiber

   Pages 43-59

6. The Fractional Quantum Hall State-to-Nematic Phase Transition Under Hydrostatic Pressure

   • Katherine A. Schreiber

   Pages 61-76

7. Universality of the Fractional Quantum Hall State-to-Nematic Phase Transition at Half-Filling in the Second Landau Level

   • Katherine A. Schreiber

   Pages 77-89

8. Origin of the Fractional Quantum Hall State-to-Nematic Phase Transition in the Second Landau Level

   • Katherine A. Schreiber

   Pages 91-101

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.

• fractional quantum hall state
• nematicity
• composite fermion
• hydrostatic pressure
• quantum phase transition
• quantum Hall nematic phase
• fractional quantum Hall state-to-nematic phase transition
• gallium arsenide

• National High Magnetic Field Laboratory - Pulsed Field Facility, Los Alamos National Laboratory, Los Alamos, USA

  Katherine A. Schreiber

Katherine Schreiber is a postdoctoral researcher at the National High Magnetic Field Laboratory at Los Alamos National Laboratory. She received her PhD from Purdue University in 2018.

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