Superconductivity in Metal-Rich Chalcogenide Ta2Se

TL;DR

This paper reports the discovery of superconductivity at 3.8 K in the layered metal-rich chalcogenide Ta2Se, highlighting its unique structure and electronic properties influenced by van Hove singularities and spin-orbit coupling.

Contribution

It provides the first experimental and theoretical investigation of superconductivity in Ta2Se, revealing its distinct properties from related compounds.

Findings

Superconductivity observed at Tc = 3.8 K in Ta2Se.

Layered tetragonal structure with Se-Ta-Ta-Ta-Ta-Se networks.

Van Hove singularities near the Fermi level influenced by spin-orbit coupling.

Abstract

The metal-metal bond in metal-rich chalcogenide is known to exhibit various structures and dominate interesting physical properties. Ta2Se can be obtained by both arc-melting and solid-state pellet methods. Ta2Se crystallizes a layered tetragonal structure with space group P4/nmm (S.G.129, Pearson symbol tP6). Each unit cell consists of four layers of body-centered closed packing Ta atoms sandwiched between two square nets of Se atoms, forming the Se-Ta-Ta-Ta-Ta-Se networks. A combined result of magnetic susceptibility, resistivity, and heat capacity measurements on Ta2Se indicate the bulk superconductivity with Tc = 3.8 (1) K. According to the first-principal calculations, the d orbitals in Ta atoms dominate the Fermi level in Ta2Se. The flat bands at gamma-point in the Brillouin zone (BZ) yield to the van Hove singularities in density of states (DOS) around the Fermi level, which is intensified by introducing spin-orbit coupling (SOC) effect, thus, could be critical for the superconductivity in Ta2Se. The physical properties especially superconductivity is completely different from Ta-rich alloys or transition metal dichalcogenide TaSe2.