Direct evidence of intercalation in a topological insulator turned   superconductor
  A topological insulator Bi2Se3 which shows superconducting property due to Cu doping has been studied using high resolution transmission electron microscopy which provides for the first time, the direct evidence of intercalation sites. A careful study exhibits the presence of two intercalation sites in this material when projected along the [-1-1 2 0] direction. Stoichiometry of the intercalated unit cell was also calculated from the projected potential. 
Tanmay Das, Somnath Bhattacharyya, Bhanu Prakash Joshi, A. Thamizhavel   and S. Ramakrishnan
cond-mat.mtrl-sci