Robust Superconductivity in (Zn_xCu_1–x)_0.5IrTe₂

Abstract

Here, we report the effect of electron doping Zn for Cu on the physical properties of Cu0.5IrTe2. Slight Zn doping concentration (x) becomes detrimental to the charge density wave (CDW) order, while the superconducting state can persist over a large change in chemical composition. The x dependence of the superconducting transition temperature (T c) exhibits a weak dome-like shape with the highest T c of 2.82 K at x = 0.5, whereas there is only a subtle change in T c. The normalized electronic specific heat ΔC el./γT c value of 1.45 for the optimal doping composition Zn0.25Cu0.25IrTe2 approaches the Bardeen–Cooper–Schrieffer (BCS) value (1.43), indicating the bulk nature of superconductivity. Magnetization and resistivity results further imply that our Zn-doped Cu0.5IrTe2 are type II superconductors. We propose that these robust (Zn x Cu1–x )0.5IrTe2 (0 ≤ x ≤ 0.9) superconductors may be suited to some research based on exfoliated crystal flakes and film devices.

Superconducting dome associated with the suppression and re-emergence of charge density wave states upon sulfur substitution in CuIr2Te4 chalcogenides

“…Concretely, the CDW signature in the resistivity disappears with a small S doping content x, whereas it reemerges for 0.2 x 0.5 and is enhanced as x increases in the doping range of 0.2 to 0.5. This phenomenon is similar to the case of single doped Cu 1−x Ag x Ir 2−y Zr y Te 4−z (I/Se) z [22,32,60,61], but it differs from the CuIr 2−x (Ru/Ti) x Te 4 and Cu 0.5−x Zn x IrTe 2 systems without reappearance of CDW transition in the high doping range [21,31,62]. Meanwhile, light blue represents the emergence and evolution of SC upon sulfur substitution, in which a small amount S substitution for Te can slightly enhance the T c and yields the highest T c of about 2.82 K at x = 0.15 for which the improvement of the SC may be due to the enhanced in electron-phonon coupling induced by the S doping, followed by a drop of T c where the degradation of T c is may due to the continuous shrinkage of the lattice which is not beneficial for the SC, which was observed in some other reported superconductors…”

“…Correspondingly, we can further calculate the Ginzburg-Landau coherence length ξ GL (0) from the formula H c2 = ϕ 0 /2πξ 2 GL , using the H c2 (0) data from the WHH model, where the flux quantum φ 0 = 2.07 × 10 −3 T μm 2 . The calculated values of ξ GL (0)s for CuIr 2 Te 3.9 S 0.05 , CuIr 2 Te 3.925 S 0.075 and CuIr 2 Te 3.85 S 0.15 are [20] T e 4 [21] I 0.1 [23] T e 2 [22] T e 4 [59] S e 0.1 [32] T e 4 [57] T c (K) 3.17 47.81, 42.88 and 45.21 nm, respectively. On the other hand, μ 0 H c1 is correlated to the coherence length ξ and the magnetic penetration depth λ through the relation μ 0 H c1 = (φ 0 /4πλ 2 ) [ln(κ) + 0.5], where κ = λ/ξ is the GL parameter [55].…”

“…The first-principles calculation analysis implies that the density of states (DOS) near the Fermi energy for CuIr 2 Te 4 mainly originates from the Ir d and Te p orbitals [20]. Subsequently, it is experimentally proved that the CDW and SC are both sensitive to the diverse chemical dopants and the three doping sites (Cu-site, Ir-site and Te-site) in the pristine CuIr 2 Te 4 [21][22][23]. Therefore, it is still of interest to explore the path from the layer CuIr 2 Te 4 chalcogenide to the CuIr 2 S 4 spinel by chemical alloying.…”

Anomalous charge density wave state evolution and dome-like superconductivity in CuIr2Te4−x Se x chalcogenides

“…Unexpectedly, the higher Se concentration (x > 0.2) induces the reappearance of CDWlike state with a lower transition value than that of the Sefree host material. Such tendency of CDW has been found by iodine doping for Te [57] but not by Zn doping in Cu site or Ru, Al, Ti doping in Ir site [58][59][60]. Thus, the CDWlike transition in this system seems to be dopant-dependent.…”