Structural phase transitions and superconductivity induced in antiperovskite phosphide CaPd${}_3$P

Abstract

In this study, we succeeded in synthesizing new antiperovskite phosphides $M$Pd${}_3$P ($M$ = Ca, Sr, Ba) and discovered the appearance of a superconducting phase (0.17 $\le$ $x$ $\le$ 0.55) in a solid solution (Ca${}_{1-x}$Sr${}_x$)Pd${}_3$P. Three perovskite-related crystal structures were identified in (Ca${}_{1-x}$Sr${}_x$)Pd${}_3$P and a phase diagram was built on the basis of experimental results. The first phase transition from centrosymmetric ($Pnma$) to non-centrosymmetric orthorhombic ($Aba$2) occurred in CaPd${}_3$P near room temperature. The phase transition temperature decreased as Ca${}^{2+}$ was replaced with a larger-sized isovalent Sr${}^{2+}$. Bulk superconductivity at a critical temperature ($T$${}_c$) of approximately 3.5 K was observed in a range of $x$ = 0.17 - 0.55; this was associated with the centrosymmetric orthorhombic phase. Thereafter, a non-centrosymmetric tetragonal phase ($I$41$md$) remained stable for 0.6 $\le$ $x$ $\le$ 1.0, and superconductivity was significantly suppressed as samples with $x$ = 0.75 and 1.0 showed ($T$${}_c$) values as low as 0.32 K and 57 mK, respectively. For further substitution with a larger-sized isovalent Ba${}^{2+}$, namely (Sr${}_{1-y}$Ba${}_y$)Pd${}_3$P, the tetragonal phase continued throughout the composition range. BaPd${}_3$P no longer showed superconductivity down to 20 mK. Since the inversion symmetry of structure and superconductivity can be precisely controlled in (Ca${}_{1-x}$Sr${}_x$)Pd${}_3$P, this material may offer a unique opportunity to study the relationship between inversion symmetry and superconductivity.

7 pages, 8 figures, 3 tables

References in corpus (1)

• Spin Triplet Superconducting State due to Broken Inversion Symmetry in Li_2Pt_3B

Cited by in corpus (1)

• Hidden Structural and Superconducting Phase Induced in Antiperovskite Arsenide SrPd${}_3$As