Nonmagnetic band gap at the Dirac point of the magnetic topological insulator (Bi1−xMnx)2Se3

• Published in: Nature communications 2016-02, Vol.7 (1), p.10559-10, Article 10559
• Main Authors: Sánchez-Barriga, J., Varykhalov, A., Springholz, G., Steiner, H., Kirchschlager, R., Bauer, G., Caha, O., Schierle, E., Weschke, E., Ünal, A. A., Valencia, S., Dunst, M., Braun, J., Ebert, H., Minár, J., Golias, E., Yashina, L. V., Ney, A., Holý, V., Rader, O.
• Format: Article
• Language: English
• Subjects: 140/146; 639/301/119/2792; 639/301/119/997; Humanities and Social Sciences; multidisciplinary; Science; Science (multidisciplinary)
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/ncomms10559

Magnetic doping is expected to open a band gap at the Dirac point of topological insulators by breaking time-reversal symmetry and to enable novel topological phases. Epitaxial (Bi 1− x Mn x ) 2 Se 3 is a prototypical magnetic topological insulator with a pronounced surface band gap of ∼100 meV. We show that this gap is neither due to ferromagnetic order in the bulk or at the surface nor to the local magnetic moment of the Mn, making the system unsuitable for realizing the novel phases. We further show that Mn doping does not affect the inverted bulk band gap and the system remains topologically nontrivial. We suggest that strong resonant scattering processes cause the gap at the Dirac point and support this by the observation of in-gap states using resonant photoemission. Our findings establish a mechanism for gap opening in topological surface states which challenges the currently known conditions for topological protection. Doping a topological insulator with magnetic impurities is expected to induce ferromagnetism and open a band gap in its surface states. Here, the authors study Mn-doped Bi 2 Se 3 , finding a mechanism for band gap opening in topologically-protected surface states which is not of magnetic origin.