Creating, manipulating, and detecting Majorana fermion states in hybrid superconductor-topological insulator Josephson devices

University Of Illinois At Urbana-Champaign, Urbana IL

Investigators

Abstract

Non-Technical Abstract: This award supports experimental research aimed at understanding a newly-discovered class of materials and enabling future advanced electronic devices. The research focuses on topological materials, called "topological" because their properties depends primarily on the topology, or geometry, of their electronic structure. By fabricating and measuring a series of advanced devices that integrate these topological materials with superconductors, the capabilities and limitations of this rapidly emerging field will be explored. In addition to their possible technological applications, these unique materials can be implemented in electronic circuits to create a new type of computer platform in which the information is stored in states protected from the detrimental effects of the environment. This is a unique feature of topological devices that has the potential to extend dramatically the speed and capability of large-scale computers. In addition to the new science and applications that may arise from this project, this research program exposes a diverse cadre of postdoctoral researchers, graduate research students, and undergraduate students to scientific issues and experimental techniques relevant to the development and applications of new materials and phenomena. This training at the interface of materials science and device physics has been demonstrated to be highly effective in launching the careers of scientists and engineers in high technology fields. Technical Abstract: Exciting new phenomena have been predicted to arise in hybrid superconductor-topological insulator systems in which pair correlations induce an effective complex superconducting order parameter exhibiting chiral edge states, topologically-protected surface states, and Majorana fermions, exotic excitations that are their own antiparticles. This project focuses on schemes to nucleate these exotic excitations and manipulate them in controllable ways to verify their existence and explore their stability and dynamics. A series of specific experiments are designed to reveal their unique non-Abelian statistics and to develop functional approaches to image, manipulate, readout the parity that encodes their critical phase information, and braid them to perform logical operations, all critical steps toward understanding the underlying physics of these novel states and crafting a technology for quantum information processing, quantum metrology, and quantum simulation/computing. Key experiments fall into four interwoven categories: (1) mapping the location of Majorana fermions via spectroscopy and imaging, looking for the zero-energy states in the gap that are signatures of these unique states, (2) probing the dynamics of Majorana fermions by phase-sensitive Josephson interferometry, searching for the periodic current-phase relation that is a characteristic signature of the Majorana fermions states, (3) manipulating and detecting the parity of Majorana fermions, exploring ways to measuring the parity via direct measurements of specific components of the supercurrent using Josephson electronics, and (4) verifying and using the non-Abelian statistics of Majorana fermions, the most characteristic and intriguing aspect of Majorana fermion modes and the property that makes them highly attractive for quantum information processing and computing. The field of topological physics is very new and researchers worldwide are collectively just starting to explore the materials, measurements, and theoretical concepts that will be important in achieving an understanding of Majorana fermions and how to exploit them in electronic circuits. This project explores the key unsolved problems in this field and paths for making significant advances in understanding the nature of exotic Majorana fermions and implementing them in functional superconductor circuits. It also provides opportunities to train students in the science and technology of this field that is anticipated to grow in the coming years.