A fractional corner anomaly reveals higher-order topology
Topological insulators (TIs) have an insulating interior and support conducting surface states with additional interfacing properties. The exotic metallic states on their surfaces can provide new routes to generate new phases and particles with potential applications in quantum computing and spintronics. Researchers have developed a theoretical framework to help identify and characterize such exotic states using new topological markers such as fractional charge density to detect topological states of matter. The resulting agreement between experimental work and theory has encouraged applications across topological platforms. In this work, Christopher W. Peterson and a team of scientists in electrical and computer engineering, physics, and mechanical science at the University of Illinois and the Pennsylvania State University in the U.S. discuss this new topological indicator introduced to identify higher-order topology and demonstrate the associated higher-order bulk-boundary correspondence. The work is now published on Science.