Preparation of new superconductors by metal doping of two-dimensional layered materials using ethylenediamine
AbstractWe have studied new superconductors prepared by metal doping of two-dimensional (2D) layered materials, FeSe and FeSe0.5Te0.5, using ethylenediamine (EDA). The superconducting transition temperatures (Tcs) of metal-doped FeSe and metal-doped FeSe0.5Te0.5, i.e., (EDA)yMxFeSe and (EDA)yMxFeSe0.5Te0.5 (M: Li, Na, and K), were 31–45 K and 19–25 K, respectively. The stoichiometry of each sample was clarified by energy dispersive x-ray (EDX) spectroscopy, and the x-ray powder diffraction pattern indicated a large expansion of lattice constant c, indicating the cointercalation of metal atoms and EDA. The pressure dependence of superconductivity in (EDA)yNaxFeSe0.5Te0.5 has been investigated at a pressure of 0–0.8GPa, showing negative pressure dependence in the same manner as (NH3)yNaxFeSe0.5Te0.5. The Tc-c phase diagrams of MxFeSe and MxFeSe0.5Te0.5 were drawn afresh from the Tc and c of (EDA)yMxFeSe and (EDA)yMxFeSe0.5Te0.5, showing that the Tc increases with increasing c but that extreme expansion of c reverses the Tc trend.