Excitonic Dark States in TMDCs (IMAGE) DOE/Lawrence Berkeley National Laboratory Caption Berkeley Lab researchers have found evidence for excitonic dark states in monolayers of tungsten disulfide that could explain the unusual optoelectronic properties of single atomic layers of transition metal dichalcogenide (TMDC) materials. Credit Image courtesy of Xiang Zhang group, Berkeley Lab Usage Restrictions None License Licensed content 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.