Structural and physical properties of the new layered transition metal material Na4Cu3TaAs4

Abstract

We report the synthesis, structural and physical properties of a new layered transition metal arsenide Na4Cu3TaAs4. This material adopts the space group I 4 ¯ 2 m , with lattice parameters of a =5.9101(3) A and c =13.8867(12) A. This structure contains two layers of Na sandwiched by anti-PbO-type (Cu/Ta)As layers, similar to the “111”-type iron-based superconductor NaFeAs. The transition metal sites are occupied by 75% Cu and 25% Ta, with Ta forming a well-defined 2 × 2 × 2 superstructure. Cu and Ta were determined to be +1 and +5 oxidation state respectively. The band structure of the Na4Cu3TaAs4 measured by angle resolved photoemission spectroscopy (ARPES) is in good agreement with the density functional theory (DFT) calculation. Both ARPES and resistivity measurement indicate that this material exhibits metallic behavior with p-type carriers. Magnetic susceptibility measurement shows that the material exhibits nearly T -independent diamagnetism. This new material extends the material system with anti-PbO-type layers and offers a good playground to investigate this material system further.