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Anomalies in the electronic structure of Bi(2)Se(3)

We studied the electronic structure Bi(2)Se(3) employing density functional theory. The calculations show that the Dirac states primarily consists of the states at the interface of surface and sub-surface quintuple layers and the emergence of the Dirac states depends on the surface terminations in sharp contrast to their surface character expected for such systems. This manifests the complexity of real materials and the realization of topological order in real materials as an outstanding problem. We discover that the surface character of the Dirac states can be achieved by adsorption of oxygen on Bi-terminated surface due to the change in covalency by the relatively more electronegative oxygens.