Superconductivity at 28.3 and 17.1 K in (Ca4Al2O6-y)(Fe2Pn2) (Pn = As and P)

TL;DR

This paper reports the synthesis of a new iron-pnictide superconductor with the highest transition temperatures among similar compounds, achieved through high-pressure techniques, highlighting unique structural features linked to superconductivity.

Contribution

The study introduces a novel high-pressure synthesis method for (Ca4Al2O6-y)(Fe2Pn2) compounds with record low lattice parameters and demonstrates their superconductivity at notable transition temperatures.

Findings

Superconductivity observed at 28.3 K and 17.1 K for Pn = As and P.

Al-42622(Pn) has the smallest lattice parameters among iron-pnictide superconductors.

Unique structural features correlate with superconducting properties.

Abstract

We have successfully synthesized (Ca4Al2O6-y)(Fe2Pn2) (Pn = As and P) (Al-42622(Pn)) using high-pressure synthesis technique. Al-42622(Pn) exhibit superconductivity for both Pn = As and P with the transition temperatures of 28.3 K and 17.1 K, respectively. The a-lattice parameters of Al-42622(Pn) (a = 3.713 {\AA} and 3.692 {\AA} for Pn = As and P, respectively) are smallest among the iron-pnictide superconductors. Correspondingly, Al-42622(As) has the smallest As-Fe-As bond angle (102.1 {\deg}) and the largest As distance from the Fe planes (1.500 {\AA}).