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Jeudi 27 Octobre
Attention !! Séminaire annulé
Iron-based superconductors on topological insulators investigated by spin-resolved scanning tunneling spectroscopy
Topological insulators and interfacial superconductors are both topics of intense current interest in modern condensed matter physics. The combination of both materials is expected to reveal novel physics such as, e.g., Majorana Fermions arising in heterostructures of topological insulators and s-wave superconductors by including magnetic fields. Interestingly, it was recently shown by transport measurements, that superconductivity can emerge at the interface of a topological insulator (Bi2Te3) and the usually non-superconducting parent compound of the Fe-chalcogenide family Fe1+ySe1-xTex (x=1) [1]. It was proposed that the topological surface state may dope the FeTe layers and suppress the long-range diagonal double-stripe antiferromagnetic spin-structure at the interface, thereby inducing the observed interfacial superconductivity. However, the spin-structure of the interface layer was not experimentally studied so far.
Here, I will review our recent investigation of the local superconducting and magnetic properties of single-layer thin films of Fe1+yTexSe1-x (x=0, 0.5, 1) grown on Bi2TexSe3-x (x=0, 2, 3) by low-temperature spin-resolved scanning tunneling spectroscopy [2-5]. While there is no indication for superconductivity in FeSe on Bi2Se3 down to T = 6 K [2], FeTe0.5Se0.5 on Bi2Te2Se shows a fully developed, temperature dependent gap suggesting a superconducting transition at a critical temperature of Tc = 12 K, close to the bulk TC value [3]. In the latter material, gap maps and Bogoliubov quasiparticle interferences reveal strong breaking to two-fold symmetry. Most notably, FeTe on Bi2Te3 shows a temperature dependent gap indicating superconducting correlations below Tc = 6 K which spatially coexist with a long-range diagonal double-stripe antiferromagnetic spin-structure [4], that is reoriented with respect to the bulk spin-order [5].
[1] Q. L. He et al., Nature comm. 5, 4247 (2014).
[2] U. R. Singh, J. Warmuth, V. Markmann, J. Wiebe, and R. Wiesendanger, arXiv:1607.02097 [cond-mat.supr-con], accepted for publication at Journal of Physics : Condensed Matter (2016).
[3] A. Kamlapure, S. Manna, L. Cornils, T. Hänke, M. Bremholm, Ph. Hofmann, J. Wiebe, and R. Wiesendanger, arXiv:1608.03827 [cond-mat.supr-con] (2016).
[4] S. Manna, A. Kamlapure, L. Cornils, T. Hänke, E. M. J. Hedegaard, M. Bremholm, B. B. Iversen, Ph. Hofmann, J. Wiebe, and R. Wiesendanger, arXiv:1606.03249 [cond-mat.supr-con] (2016).
[5] T. Hänke, U. R. Singh, L. Cornils, S. Manna, A. Kamlapure, M. Bremholm, E. M. J. Hedegaard, B. B. Iversen, Ph. Hofmann, J. Hu, Z. Mao, J. Wiebe, and Roland Wiesendanger, arXiv:1606.09192 [cond-mat.str-el] (2016).