Superconductivity without Fe or Ni in the phosphidesBaIr2P2andBaRh2P

Electron-phonon superconductivity in the ternary phosphidesBaM2P2(M=Ni,Rh,a

“…In general, the calculated lattice parameters and internal parameters for all the ternary phosphides BaM 2 P 2 are in good accordance with previous experimental [20,25,27,28,32] and theoretical [17,24,30] results. The maximum difference in the lattice parameters is around 2.0% for all the studied compounds, while the maximum difference in the internal parameter z is around 0.7% for BaNi 2 P 2 .…”

“…By integrating the Eliashberg spectral function, the average electron-phonon coupling parameter is determined for all the studied ternary phosphides. Finally, the calculated superconducting parameters for all the studied ternary phosphides are found in gratifying agreement with their corresponding experimental values [19,25,32,33].…”

“…Thus, it is interesting to find compounds that adopt the ThCr 2 Si 2 -type structure but do not include Fe or Ni. In 2009, heat capacity, resistivity, and magnetic susceptibility measurements suggested bulk superconductivity in single crystals of BaIr 2 P 2 (T c = 2.1 K) and BaRh 2 P 2 (T c = 1.0 K) [25,26]. These two materials, known since the early work of Wurth et al [27] and Lökhen et al [28], are isostructural to LaRu 2 P 2 and illustrate the existence of superconductivity over a large variety of layered transition metal pnictides.…”

“…In addition to this theoretical work, the structural and electronic properties of BaRh 2 P 2 and BaIr 2 P 2 have been investigated using the full-potential linearized augmented plane-waves (FP-LAPW) method and a generalized gradient approximation (GGA) for the exchange correlation potential [30]. The theoretical work of Shein and Ivanovskii indicates that the density of states at the Fermi level for BaRh 2 P 2 is larger than that for BaIr 2 P 2 although the T c value of BaRh 2 P 2 [25,26] is considerably lower than that of BaIr 2 P 2 . This led Shein and Ivanovskii to state that an increase in T c from 1.0 K for BaRh 2 P 2 to 2.1 K for BaIr 2 P 2 can be related to the difference in the vibrational properties of these materials rather than the electronic properties of them.…”

“…This led Shein and Ivanovskii to state that an increase in T c from 1.0 K for BaRh 2 P 2 to 2.1 K for BaIr 2 P 2 can be related to the difference in the vibrational properties of these materials rather than the electronic properties of them. Available experimental [25,26,31] and theoretical studies [29][30][31] on ternary phosphide superconductors signal that the lack of interlayer P-P bonding is crucial for superconductivity in these materials. According to these studies AM 2 P 2 materials can be categorized in two groups of extremely different P-P interatomic distances along the z direction.…”