Twisted graphene reveals a hidden superconductivity switch

Superconductivity allows certain materials to carry electricity with zero energy loss when cooled below a critical temperature. Even though scientists have studied the phenomenon for decades, many of its underlying mechanisms remain poorly understood. Gaining deeper insight into how superconductivity forms could help researchers design better materials and improve future electronic and quantum devices.

Twisted Graphene Reveals Unusual Behavior

The study, led by Chun Ning (Jeanie) Lau, a physics professor at The Ohio State University, focused on a specially engineered material known as twisted bilayer graphene. The material is made by stacking two sheets of carbon and rotating one slightly relative to the other.

The research team combined the graphene structure with strontium titanate, a synthetic diamond-like material. This setup allowed scientists to observe and influence how electrons interacted inside the system.

Electron interactions play a major role in determining properties such as magnetism and chemical bonding. In superconductors, electrons pair together in a special way that enables electricity to flow without resistance. By tuning the environment around the material, the team found they could strengthen or weaken those interactions and effectively switch superconductivity on and off.

"Electrons normally repel each other, but in superconductors they form pairs; this pair formation is the key to a superconductor's ability to conduct electricity without dissipation," said Lau. "Our evidence suggests that electrons themselves, depending on their sensitivity to their nearby environment, are unexpectedly important for material changes."

Discovery Challenges Traditional Superconductor Theory

The researchers were surprised by one of their findings. As they increased certain adjustments within the material, superconductivity became weaker instead of stronger.

That behavior differs from what scientists typically observe in conventional superconductors, where reducing the repulsive forces between electrons usually strengthens superconductivity. The unexpected result highlights how unusual materials like twisted bilayer graphene may behave very differently from traditional superconductors.

"If you could transmit electricity without energy loss, that would be hugely important for technologies used in our everyday life," said Lau. "Despite the fundamental questions that still need answers, this work basically provides a path toward a new type of physics mechanism."

The discovery may also help researchers move closer to one of the field's biggest goals: developing superconductors that work at much higher temperatures, potentially even room temperature. Achieving that milestone could dramatically reshape electronics, communications systems, and power transmission technologies.

Potential for More Efficient Electronics

The findings, published in Nature Physics, suggest a simpler method for controlling the conditions needed to create superconductivity.

Many high-temperature superconductors currently face limitations that reduce their performance. The researchers believe manipulating the surrounding environment of these materials could provide a new way to improve their capabilities and increase efficiency in future electronics.

According to lead author Xueshi Gao, a PhD student in physics at Ohio State, the team expects the results to become useful for many different experiments and material systems across the field.

"The mechanism of superconductivity in the twisted bilayer graphene system we used is still not well understood," said Gao. "But our result can shed light on and help people to better understand the concept when applying it to future work."

Researchers Plan Further Experiments

The scientists caution that the work represents an early step toward understanding a much broader range of complex electronic interactions. Future research will explore other interaction types and investigate additional physics questions raised by the study.

"We're showing capabilities that we haven't shown before, so many people in the field are getting really excited about this result," said Lau.

Additional co-authors from Ohio State include Aatmaj Rajesh, Emilio Codecido, Daria Sharifi, Zheneng Zhang, Youwei Liu and Marc Bockrath. Collaborators also included Alejandro Jimeno-Pozo, Pierre Pantaleon and Paco Guinea from Imdea Nanoscience in Spain, along with Kenji Watanabe and Takashi Taniguchi from the National Institute for Materials Science in Japan.

The research was supported by the Department of Energy and the National Science Foundation.