Topological Insulator Band Structure (IMAGE) DOE/Lawrence Berkeley National Laboratory Caption ARPES maps the electronic properties, including the band structure and Fermi surface, of the topological insulator bismuth selenide (left). Like graphene, the lower energy valence band of a topological insulator meets the higher energy conduction band at a point, the Dirac point, with no gap between the bands (center). Unlike graphene, however, the Fermi surface does not usually pass through the Dirac point. Distinct spin states (red arrows) are associated with each different orientation in momentum space (right). Credit Lawrence Berkeley National Laboratory 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.