FSU Physicists Discover Superconducting and Topological States in Rhombohedral Graphene

Rhombohedral Graphene Reveals Unusual Superconducting and Topological States

A team of physicists, including researchers from Florida State University (FSU), has observed a rare combination of superconducting and topological states in a simple, naturally occurring material system. The findings, published in Nature Physics, could pave the way for new quantum computing technologies.

The discovery centers on rhombohedral graphene, a few layers of carbon atoms stacked in a specific, chiral pattern. This structure naturally confines electrons to the top and bottom surfaces of the material, creating a unique environment for correlated electronic behavior.

"The system captures phenomena seen in other atomically thin systems but with reduced complexity and improved replicability."
— Cyprian Lewandowski, FSU Physicist

Unlike many complex, engineered materials, this system does not require manual construction. The dual-surface geometry occurs naturally, isolating electron and hole carriers on opposite surfaces.

• Coexistence of Charges: Researchers found that negative and positive charges coexist within the system, a key ingredient for the observed superconductivity.
• The Interaction: Superconductivity emerges from the interaction between these electron and hole carriers on the opposing surfaces.
• Topological State: In addition to superconductivity, the team observed a quantum anomalous Hall effect—a topological state where electrical current flows along the edges without any resistance.

This coexistence of superconductivity and topological states is significant because it is a theoretical prerequisite for creating Majorana zero modes. These exotic particles are considered a cornerstone for building fault-tolerant quantum computers.

"The coexistence of superconductivity and topological states could enable Majorana zero modes for fault-tolerant quantum computing."
— Mike Shatruk, FSU Professor of Chemistry & Biochemistry

The research advances the fundamental understanding of strongly correlated and topological phases of matter. Because the material is naturally occurring and highly replicable, it offers a more practical platform for exploring these rare quantum phenomena.

Matthew Yankowitz, a collaborator on the project, noted the unusual nature of the charge distribution. "Negative and positive charges coexist in the system," he said, highlighting the material's unique properties.

The work was supported by the U.S. Army Research Office, the U.S. Department of Energy, the National Science Foundation, and FSU. The international collaboration includes researchers from the University of Washington, the University of British Columbia, and Japan's National Institute for Materials Science.