Superconductivity in Ca_1-<i>x</i>La_<i>x</i>FeAs₂: A Novel 112-Type Iron Pnictide with Arsenic Zigzag Bonds

Abstract

We report superconductivity in the novel 112-type iron-based compound\nCa1-xLaxFeAs2. Single-crystal X-ray diffraction analysis revealed that the\ncompound crystallizes in a monoclinic structure (space group P21), in which\nFe2As2 layers alternate with Ca2As2 spacer layers such that monovalent arsenic\nforms zigzag chains. Superconductivity with a transition temperature (Tc) of 34\nK was observed for the x = 0.1 sample, while the x = 0.21 sample exhibited\ntrace superconductivity at 45 K. First-principles band calculations\ndemonstrated the presence of almost cylindrical Fermi surfaces, favorable for\nthe high Tc in La-doped CaFeAs2.\n