Absence of superconductivity in ultra-thin layers of FeSe synthesized on   a topological insulator
  The structural and electronic properties of FeSe ultra-thin layers on Bi$_{2}$Se$_{3}$ have been investigated with a combination of scanning tunneling microscopy and spectroscopy and angle-resolved photoemission spectroscopy. The FeSe multi-layers, which are predominantly 3-5 monolayers (ML) thick, exhibit a hole pocket-like electron band at \bar{\Gamma} and a dumbbell-like feature at \bar{M}, similar to multi-layers of FeSe on SrTiO$_{3}$. Moreover, the topological state of the Bi2Se3 is preserved beneath the FeSe layer, as indicated by a heavily \it{n}-doped Dirac cone. Low temperature STS does not exhibit a superconducting gap for any investigated thickness down to a temperature of 5 K. 
Andreas Eich, Nils Rollfing, Fabian Arnold, Charlotte Sanders, Pascal   R. Ewen, Marco Bianchi, Maciej Dendzik, Matteo Michi...
cond-mat.supr-con cond-mat.mes-hall cond-mat.mtrl-sci