Mott insulator image (IMAGE) Brown University Caption The researchers found the key to their theory is an unexpected collection of particles called bipolarons that form when electronic charge is added to the material. Credit Photo provided by Mitrović Lab. Usage Restrictions Credit must be given to the creator. License CC BY Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.