Superconductivity in a new layered triangular-lattice system Li2IrSi2

Abstract

We report on the crystal structure and superconducting properties of a novel iridium-silicide, namely Li _2 IrSi _2 . It has a Ag _2 NiO _2 -type structure (space group R-3m) with the lattice parameters a = 4.028 30(6) Å and c = 13.161 80(15) Å. The crystal structure comprises IrSi _2 and double Li layers stacked alternately along the c -axis. The IrSi _2 layer includes a two-dimensional Ir equilateral-triangular lattice. Electrical resistivity and static magnetic measurements revealed that Li _2 IrSi _2 is a type-II superconductor with critical temperature ( T _c ) of 3.3 K. We estimated the following superconducting parameters: lower critical field H _c1 (0) ∼ 42 Oe, upper critical field H _c2 (0) ∼ 1.7 kOe, penetration depth λ _0 ∼ 265 nm, coherence length ξ _0 ∼ 44 nm, and Ginzburg–Landau parameter κ _GL ∼ 6.02. The specific-heat data suggested that superconductivity in Li _2 IrSi _2 could be attributed to weak-coupling Cooper pairs.

Keywords

• supreconductivity
• iridium-silicide
• spin–orbit coupling