3-D Topological Dirac Semi-Metal (image) DOE/Lawrence Berkeley National Laboratory Caption A topological Dirac semi-metal state is realized at the critical point in the phase transition from a normal insulator to a topological insulator. The + and - signs denote the even and odd parity of the energy bands. Credit (courtesy of Yulin Chen, Oxford) Usage Restrictions None 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.