Purely Magnetic Impurities

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Science  05 Apr 2013:
Vol. 340, Issue 6128, pp. 10-11
DOI: 10.1126/science.340.6128.10-e

Magnetically doped topological insulators (TIs) have been predicted to exhibit a host of exotic properties stemming from the breaking of time-reversal symmetry caused by magnetic impurities. However, dopants such as iron or manganese also have a charge effect, which distorts the original electronic structure and makes it difficult to isolate the effects of magnetism. Schlenk et al. devised a procedure for magnetic doping that aims to circumvent this problem and which should help to provide insight into the effects of time-reversal symmetry-breaking in TIs. They deposited Fe atoms on the surface of cold samples of the topological insulator Bi2Se3 and then annealed them at much higher temperatures. Scanning tunneling microscopy indicated that the annealing caused the dopants, initially adatoms, to descend into the material; angle-resolved photoemission found the electronic structure, initially distorted by depositing the adatoms, to be restored after the annealing step. First-principles calculations further indicated that the Fe atoms were probably substituting Bi atoms, and that whereas adatoms acted as electron donors, the buried Fe atoms were either neutral or acceptors; the magnetic interaction with the host material was also found to be enhanced with respect to the case of adatoms.

Phys. Rev. Lett. 110, 126804 (2013).

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