Magneto-Optics Of Massive Dirac Fermions In Bulk Bi2se3

We report on magneto-optical studies of Bi2Se3, a representative member of the 3D topological insulator family. Its electronic states in bulk are shown to be well described by a simple Dirac-type Hamiltonian for massive particles with only two parameters: the fundamental band gap and the band velocity. In a magnetic field, this model implies a unique property-spin splitting equal to twice the cyclotron energy: E-s = 2E(c). This explains the extensive magnetotransport studies concluding a fortuitous degeneracy of the spin and orbital split Landau levels in this material. The E-s = 2E(c) match differentiates the massive Dirac electrons in bulk Bi2Se3 from those in quantum electrodynamics, for which E-s = E-c always holds.