Superconductivity induced by Mg deficiency in noncentrosymmetric phosphide Mg2Rh3P

The search for noncentrosymmetric superconductors that may exhibit unusual physical properties and unconventional superconductivity has yielded the synthesis of a noncentrosymmetric phosphide Mg2Rh3P with an Al2Mo3C-type structure. Although stoichiometric Mg2Rh3P does not exhibit superconductivity at temperatures above 2 K, we found that an Mg deficiency of approximately 5 at.% in the Mg2Rh3P-induced superconductivity at 3.9 K. Physical properties such as the lattice parameter a = 7.0881 angstrom, Sommerfeld constant gamma(n) = 5.36 mJ mol(-1) K-2, specific heat jump Delta C-el/gamma T-n(c) = 0.72, electron-phonon coupling constant lambda(e-p) = 0.58, upper critical field H-c2 (0) = 24.3 kOe, and pressure effect dT(c)/dP = -0.34 K/GPa were measured for the superconducting Mg2-delta Rh3P (delta similar to 0.1). Band-structure calculations indicate that exotic fermions, which are not present in high-energy physics, exist in Mg2Rh3P. Since Mg, Rh, and P are the first elements used at each crystal site of Al2Mo3C-type compounds, the discovery of Mg2Rh3P may guide the search for new related materials.