Dresden 2011 – scientific programme

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MA: Fachverband Magnetismus

MA 63: Poster II (Surface Magnetism/ Magnetic Imaging/ Topological Insulators/ Spin Structures and Magnetic Phase Transitions/ Graphene/ Magnetic Thin Films/ Magnetic Semiconductors/ Magnetic Half-metals and Oxides/ Spin-dependent Transport/ Spin Excitations and Spin Torque/ Spin Injection and Spin Currents in Heterostructures/ Spintronics/ Magnetic Storage and Applications)

MA 63.15: Poster

Friday, March 18, 2011, 11:00–14:00, P2

Bulk vs. surface effects in ARPES experiments on the topological insulator Bi₂Se₃ — •Richard C. Hatch¹, Marco Bianchi¹, Dandan Guan^1,2, Shining Bao², Jianli Mi³, Bo Brummerstedt Iversen³, and Philip Hofmann¹ — ¹Department of Physics and Astronomy, Interdisciplinary Nanoscience Center Århus University, 8000 Århus C, Denmark — ²Department of Physics, Zhejiang University, Hangzhou, 310027 China — ³Department of Chemistry, Interdisciplinary Nanoscience Center, Århus University, 8000 Århus C, Denmark

While the bulk of a topological insulator is insulating, fundamental symmetry considerations require the surfaces to be metallic. The dimensionality of states in the topological insulator Bi₂Se₃ were probed directly by performing ARPES measurements at different photon energies along ΓK and ΓM. It was found that both the topological surface state and the state attributed to a two-dimensional electron gas [1] do not disperse with respect to the wave vector perpendicular to the surface k_z—thus confirming their two-dimensional nature. In contrast, strong k_z dispersions of the bulk conduction and valence bands are evident. From the experimental data, we derive the bulk band structure in the two high-symmetry slices throughout the Brillouin zone. Finally, we observe a state at a binding energy of 750 meV which does not disperse with k_z and is interpreted to be another surface state situated in a projected bulk band gap below the upper valence band.

[1] M. Bianchi et al. Nat. Communications 2010, DOI 10.1038/NComms1131.