Dresden 2026 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 5: Surface Magnetism and Topological Insulators (joint session MA/TT)

MA 5.7: Vortrag

Montag, 9. März 2026, 11:15–11:30, POT/0351

Hidden Dirac-Like Crossings in a Prototypical Topological Insulator — •Wei-Sheng Chiu^1,2, Ina Marie Verzola³, Ying-Jiun Chen¹, Rovi Angelo Beloya Villaos³, Claus Michael Schneider^1,2, Feng-Chuan Chuang³, and Christian Tusche^1,2 — ¹Forschungszentrum Jülich, Germany — ²Universität Duisburg-Essen, Germany — ³National Sun Yat-sen University, Taiwan

The prototypical topological insulator Bi₂Se₃ has been extensively studied for its topological surface state characterized by a Z₂ topological invariant. By using spin-resolving momentum microscopy with an Au passivated Ir(100) imaging spin filter, we simultaneously recorded the spin-resolved momentum maps (k_x,k_y) over entire surface Brillouin zone of Bi₂Se₃. In addition to the well-known Dirac cone near Fermi energy, we observe a sequence of several Dirac-like spin textures and crossings spanning binding energies down to 4 eV at the Γ point. Moreover, a Dirac-like crossing is also found at a binding energy 2.3 eV at the M point. Our first-principles calculations indicate that those overlooked bands are attributed to surface states. The Dirac-like crossing at the M point arises from crystalline-symmetry-enforced degeneracy at the high symmetry point, showing that Bi₂Se₃ has a more complex surface electronic structure than previously expected.

Keywords: Topology; Spin-resolving momentum microscopy; Photoemission; Spin textures; Dirac cones