- Karel Carva: The role of native defects and magnetic dopants in topological insulators Bi2Te3 and Bi2Se3
- 8. 2. 2017, 14:30
- lecture room F2, first floor Ke Karlovu 5
- more information
Abstract:
Topological insulators exhibit highly interesting features, these are however predicted for ideal samples. Here we examine the influence of probable native defects, as well as an intentional magnetic doping. Magnetic order is expected to affect strongly topological insulator prooperties [1]. We calculate on ab initio level electronic structure of Bi2Te3 and Bi2Se3 doped by Mn at different possible positions in the lattice and also in the presence of antisites and vacancies. This provides for the first time a comprehensive map of possible behavior affecting strongly the bulk resistivity, carrier concentration and magnetism [2]. Density of states calculations reveal in which case the Fermi level lies at low conducting impurity Mn peak and which effects shift it. This allows us to tune the bulk resistivity, and also help to uncover the location of Mn atoms. Concentration dependence of resistivity exhibits significant difference between substitutional or interstitial Mn position. Calculations indicate that at least two of the considered defects have to be present simultaneously in order to explain the observations, and the role of interstitials may be more important than expected.
Exchange interactions between the Mn magnetic moments in bulk Mn-doped Bi2Se3 and Bi2Te3 have been calculated using ab initio methods. Ferromagnetic Curie temperature and other magnetic magnetic properties are systematically studied by means of atomistic Monte Carlo simulations. We find that the ferromagnetic ordering is possible for some configurations, and link the tendency to it to the Fermi level position. Theoretical results were compared to recent experimental studies [3].
[1] Y. S. Hor et al., Phys. Rev. B 81 (2010) 195203.
[2] K. Carva et al., Phys. Rev. B 93 (2016) 214409.
[3] R. Tarasenko et al., Physica B: Condensed Matter 481, 262 (2016)