Graphene can hold multiple states of superconductivity, a new study finds

A groundbreaking discovery has emerged from research conducted at the Massachusetts Institute of Technology (MIT), revealing that graphene—a single layer of carbon atoms—can support multiple distinct states of superconductivity. Published in the prestigious journal *Nature*, the study challenges conventional understanding of superconductivity, a phenomenon where electricity flows without resistance. Typically, superconductivity is fragile and easily disrupted by external factors such as magnetic fields. However, the MIT team found that certain configurations of graphene, specifically rhombohedral pentalayer graphene, can sustain and even enhance superconductivity in the presence of magnetic fields.

The research focused on rhombohedral graphene, a naturally occurring structure within graphite composed of four or five graphene layers stacked in a specific arrangement. Unlike traditional superconductors, which usually exhibit a single form of superconductivity, this material hosts multiple superconducting states. These states manifest as different ways in which electrons pair up and move through the material without resistance. Remarkably, some of these states remain stable or even strengthen when exposed to a magnetic field—an effect contrary to what is typically observed in superconducting materials.

Long Ju, a physicist at MIT and one of the lead researchers, emphasized the significance of the finding. “People might assume that this is a simple, boring carbon material,” he said. “But we can control this material by tuning certain experimental 'knobs,' such as electrical voltages. This is how a simple physical material can exhibit so many different superconducting properties.” The ability to manipulate superconducting states using external parameters opens new avenues for both theoretical exploration and practical applications in electronics and energy transmission.

The study’s findings suggest that rhombohedral graphene could serve as a platform for investigating unconventional superconductivity. While the exact mechanisms behind the persistence and enhancement of superconductivity in magnetic fields remain unclear, the researchers have provided substantial experimental data to guide future investigations. Understanding these phenomena could offer insights into the broader principles governing superconductivity and potentially lead to the development of novel materials with enhanced properties.

The research was conducted by a multidisciplinary team including MIT scientists and collaborators from institutions such as the University of Basel in Switzerland, Florida State University, the University of Florida, and the National Institute for Materials Science in Japan. Their combined expertise contributed to the comprehensive analysis of the material's unique characteristics.

Rhombohedral graphene is part of a growing class of two-dimensional materials that display extraordinary electronic and magnetic behaviors. When graphene layers are stacked and twisted at specific angles, they can give rise to unusual quantum phenomena. However, unlike artificial "magic-angle" graphene structures created in laboratories, the MIT team explored naturally occurring rhombohedral configurations. These structures, resembling the steps of a staircase, were found to possess intriguing electronic properties that had previously gone unnoticed.

The implications of this discovery extend beyond academic curiosity. If the mechanisms underlying the stability of superconductivity in magnetic fields can be fully understood, it could pave the way for developing materials capable of functioning efficiently in high-magnetic-field environments, such as those found in particle accelerators or medical imaging devices. Additionally, the ability to tune superconducting states through external controls offers potential applications in quantum computing and advanced sensor technologies.

As the scientific community continues to explore the properties of rhombohedral graphene, further experiments will likely focus on elucidating the fundamental physics behind its unique behavior. Researchers aim to uncover the precise conditions under which multiple superconducting states emerge and how they interact with magnetic fields. These studies could also help identify other materials with similar properties, expanding the scope of superconductivity research and its practical applications.