Interplay between strongly correlated quantum Hall states and superconductivity

Purdue University, West Lafayette IN

Investigators

Abstract

Non-technical Abstract: Electrons are charged particles, and two electrons brought close to each other repel according to the Coulomb's law. Behavior of a large number of electrons may be much more complex and sometimes counterintuitive. For example, lattice vibrations can change repulsive interactions into attractive resulting in superconductivity, a state with no resistance to electrical current. In two dimensional systems, where electrons are confined to a thin sheet of material, even more exotic states can develop in high magnetic fields. At some fields resistance vanishes, as in superconductors, but transverse (Hall) resistance remains non-zero and is quantized. Some of these states may be superconductors of a very special type, where charges are fractions of an electron charge, something impossible in a three dimensional world. After many years of studies these states are still poorly understood, primarily due to a very limited amount of tools that can be used to investigate these fragile states. Yet some of these states may possess properties necessarily to create fault tolerant quantum computers. In the past with NSF support, the PI's group developed a technology to form high quality electrical contacts between conventional superconductors and two dimensional electron systems. Our research team is now using superconductivity as a new tool to probe exotic states at high magnetic fields, a regime previously not accessible to experimental scrutiny. This research can potentially lead to the development of quantum bits where quantum information is encoded in the topology of the system. Such quantum bits are predicted to be inherently fault-tolerant. Educational and outreach goals include training students in a multidisciplinary program and organization of a Summer Physics Camp for middle school students. Technical Abstract: Among all the experimental systems high mobility two-dimensional electron gases (2DEG) play a unique role of a model system where strong electron-electron correlations lead to the formation of a plethora of exotic states at high magnetic fields, some of them predicted to form unconventional superconducting states. The PI's group's recent breakthrough in the fabrication of transparent ohmic superconducting contacts to high mobility 2DEG in GaAs opens this previously inaccessible regime of superconductor-2DEG interface to experimental scrutiny. Preliminary results indicate the limited understanding of Cooper pair injection into a quantum Hall effect regime. The research objectives include detailed investigation of interplay between topologically distinct superconductivity and strongly correlated fractional quantum Hall effect, a previously inaccessible regime where exciting new physics is waiting to be discovered. This research can potentially lead to the development of a new platform where high order non-Abelian excitations can be realized, a prerequisite for topologically protected fault-tolerant quantum computing. Educational and outreach goals include training students in a multidisciplinary program and organization of a Summer Physics Camp for middle school students.