Doping-driven structural phase transition and loss of superconductivity in MxFe1−xSeδ (M=Mn, Cu)

Abstract

In this paper, we report the results of detailed studies on Mn and Cu substitution to Fe site of β-FeSe, namely, MnxFe1−xSe1−δ and CuxFe1−xSe1−δ (δ equals to 0.03–0.05 based on our neutron-diffraction refinements). The results show that with only 10 at. % Cu doping the compound becomes a Mott insulator. Detailed temperature-dependent structural analyses of these Mn- and Cu-substituted compounds show that the structural transition, which is associated with the changes in the building block FeSe4 tetrahedron, is essential to the occurrence of superconductivity in β-FeSe. © 2010, American Physical Society