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 weakcoupling Cooper pairs.

High-pressure synthesis and superconductivity of the novel laves phase BaIr2

“…In recent years, the search for new superconductors comprising 5d transition metals of Ir and Pt has been actively conducted because of the potential of distinctive superconducting states caused by the strong spin-orbit interaction (SOI) [1][2][3][4][5][6][7][8][9][10][11]. Verifications of unconventional superconductivity in such 5d transition metal-based materials have also been vigorously pursued [12][13][14].…”

Electronic, phononic and superconducting properties of trigonal Li2 MSi2 (M = Ir, Rh)

“…The crystal structure of Li 2 IrSi 2 and Li 2 RhSi 2 compounds was reported as a trigonal in the centrosymmetric space group R 3m (No. 166) [7]. The primitive cell concern one formula unit is Li 2 IrSi 2 (Li 2 RhSi 2 ) which has 2 Li, 1 Ir (Rh) and 2 Si atoms.…”

“…Transition metal compounds have a wide diversity of structure, magnetic, and electronic properties due to their incomplete d orbital. Among the d transition-metal compounds, the 3d compounds have attracted extensive attention; because of their unique physical properties, including charge and spin ordering, colossal magnetoresistance, and high-T c superconductivity [1][2][3][4][5][6][7]. Also, the electronic states are well localized due to the large Coulomb repulsion of 3d transition-metal compounds.…”

“…There are many other examples including the elements for transition metals, which mainly include, Co, Ni, Fe, Mo, W, Mn, Cu, Ru, Pd, Ir, and Rh. Distinctively, the Ir atom related 5d and Rh atom related 4d transition-metal compounds such as M 2 Ir 2 As 2 (M = Sr, Ba, Y, La) [13][14][15][16], Ir 1−x Pt x Te 2 [17,18], Sr 2 Ir 2 [19], B 2 IrT 2 (T = Mo, V) [20], MGe (M = Rh, Pd, Ir and Pt) [21,22], MIr 2 (M = Sc, Y, La), MIr 3 (M = La, Th, Ce), MIr 5 (M = La, Th, Ce), M 5 Ir 4 Si 10 (M = Sc, Y, Lu), M 5 Ir 4 Ge 10 (M = Y, Lu) [23][24][25], MIr 2 Si 2 (M = Y, La) [26], Li 2 Ir 2 Si 3 [27,28], Li 2 IrSi 2 [7], Li 2 RhSi 2 [7], Rh 17 S 15 [12], MRh 2 Sn (M = Sc, Lu, Y) [29], Y 5 Rh 6 Sn 18 [30] were studied and their superconductivity properties were characterized. Interestingly, these compounds with the Si atoms are crystallized with polar noncentrosymmetric crystal structures [27].…”

“…According to this study, Li 2 IrSi 3 is a weakcoupling electron-phonon pairing superconductor. Recently, Horigane et al have synthesized an alkali-metal iridium silicide, which is a new ternary compound superconductor with a centrosymmetric trigonal (rhombohedral) structure, using a high-pressure synthesis technique [7]. They reported that Li 2 IrSi 2 has a layered structure composed of a plane equilateral triangle Ir lattice, and the critical temperature was found to be about ∼3.3 K and revealed that Li 2 IrSi 2 is a type-II superconductor in its magnetic and electrical resistivity measurements.…”