Fe dopants and surface adatoms versus nontrivial topology of single-crystalline Bi<sub>2</sub>Se<sub>3</sub>
M. Chrobak, Krzysztof Maćkosz, M. Jurczyszyn, M. Dobrzański, Kamil Nowak, T. Ślęzak, Marcin Zając, Marcin Sikora, Marek M. Rams, T. Eelbo, Joanna Stępień, M. Waśniowska, Olivier Mathon, F. Yakhou-Harris, D. G. Merkel, I. Miotkowski, Z. Kąkol, A. Kozłowski, M. Przybylski, Z. Tarnawski
Abstract
Abstract Both preserved gapless states and gapping of Dirac states due to broken time reversal symmetry in bismuth chalcogenide topological insulators with surface and bulk magnetic impurities have been observed and reported in the literature. In order to shed more light on the mechanism of such effects we have performed comprehensive element selective study of the impact of Fe impurity position in the Bi 2 Se 3 lattice on its magnetism. The iron atoms were imbedded in the structure (volume dopants) or deposited on the surface (adatoms) and they revealed striking phenomena. Volume doping preserves non-trivial topology of Bi 1.98 Fe 0.02 Se 3 . Fe atoms not only substitute Bi, but also locate in van der Waals gap. The former are magnetically isotropic, while the latter reveal large magnetic moment (4.5 μ B ) with perpendicular anisotropy if located near the surface. Majority of Fe adatoms on the surface of Bi 2 Se 3 exhibit weaker moment (3.5 μ B ) with in-plane anisotropy, as expected for non-interacting species. Negligible interaction between surface electronic states and magnetic adatoms is confirmed by identical vibration spectra of Fe deposited on TI surface of Bi 2 Se 3 and non-TI surface of Bi 2 S 3 . The data gathered show how indispensable is the knowledge of the magnetic impurity distribution for applications of bismuth chalcogenide systems.