Experiments on Fractional Quantum Hall Effect and Related Physics in New Regimes

Princeton University, Princeton NJ

Investigators

Abstract

In modern day electronics, almost all device functions are performed by electrons that are confined to move in thin films, or along the interfaces, of semiconductors. Such so-called two-dimensional (2D) electron systems, which behave at normal ambient as an ordinary gas of 2D particles, evolve into a new frontier of physics when they are subjected to the extreme conditions of low temperatures (T<<1K) and high magnetic fields (B>>1T). Some of the observed physical phenomena are first realizations of early theoretical predictions (e.g. the Wigner crystal and the skyrmion); others, such as composite fermions, are more recent discoveries and inventions. All represent the ultra-low energy physics manifested in the quantum mechanical principles that govern the behavior of large numbers of strongly interacting electrons in the solid state. This project will explore such ultra-low energy electron physics in previously inaccessible physical regimes of low electron densities and ultra-low temperatures, to below 1 mK. The experiments, designed to uncover new quantum phases in these regimes and to probe into their quantum phase transitions, are also expected to have broader impacts in two areas of societal importance: One is in the education and training of future leaders in science and technology with multi-disciplinary knowledge and perspectives, as well as cutting edge technical skills. The research, being multi-disciplinary in nature, will educate students and post-docs involved to be fluent in condensed matter physics, the science of semiconductor materials, and the processing technology of semiconductor devices. The other area is on the future quantum computer. The current vision for a fault-tolerant quantum computer is the one that uses nonAbelian particles. To date, the only known realization of such particles in the solid state consists of the quasi-particles of the exotic liquid condensate of paired composite fermions found in 2D electron media. In modern day electronics, almost all device functions are performed by electrons that are free to move in two dimensions in thin films, or along the interfaces, of semiconductors. Such so-called two-dimensional (2D) electrons behave at normal ambient as an ordinary gas of independent 2D particles. The behavior of a large number of them together is simply that of the sum of the individual particles, each adequately described by the classical law of physics. However, when subjected to extremely low temperatures and high magnetic fields, they become a new frontier for ultra-low energy physics, surprisingly rich in novel phases that manifest the workings of quantum physics that govern the behavior of a large number of strongly interacting electrons in the solid. This project will explore ultra-low energy electron physics in previously inaccessible physical regimes of low electron densities and low temperatures. This should uncover new quantum phases of the electrons, where they are more appropriately pictured as a new kind of exotic liquid or solid, and to probe their transformations. It is also expected to have broader impacts in the education and training of future leaders in science and technology with multi-disciplinary knowledge and perspectives, as well as cutting edge technical skills. The research, being multi-disciplinary in nature, will educate students and post-docs involved to be fluent in condensed matter physics, the science of semiconductor materials, and the processing technology of semiconductor devices.