New Intermetallic Ternary Phosphide ChalcogenideAP2−xXx(A= Zr, Hf;X= S, Se) Superconductors with PbFCl-Type Crystal Structure

Abstract

We have synthesized a series of intermetallic ternary phosphide chalcogenide superconductors, AP2−xXx (A = Zr, Hf; X = S, Se), using the high-pressure synthesis technique. These materials have a PbFCl-type crystal structure (space group P4/nmm) when x is greater than 0.3. The superconducting transition temperature Tc changes systematically with x, yielding dome-like phase diagrams. The maximum Tc is achieved at approximately x = 0.7, at which point the Tc is 6.3 K for ZrP2−xSex (x = 0.75), 5.5 K for HfP2−xSex (x = 0.7), 5.0 K for ZrP2−xSx (x = 0.675), and 4.6 K for Hfp2−xSx (x = 0.5). They are typical type-II superconductors and the upper and lower critical fields are estimated to be 2.92 T at 0 K and 0.021 T at 2 K for ZrP2−xSex (x = 0.75), respectively.