Superconductivity and Charge Density Wave in Iodine-Doped CuIr₂Te₄

Abstract

We report a systematic investigation on the evolution of the structural and physical properties, including the charge density wave (CDW) and superconductivity of the polycrystalline CuIr2Te4−x I x for 0.0 ≤ x ≤ 1.0. X-ray diffraction results indicate that both of a and c lattice parameters increase linearly when 0.0 ≤ x ≤ 1.0. The resistivity measurements indicate that the CDW is destabilized with slight x but reappears at x ≥ 0.9 with very high T CDW. Meanwhile, the superconducting transition temperature T c enhances as x increases and reaches a maximum value of around 2.95 K for the optimal composition CuIr2Te1.9I0.1 followed by a slight decrease with higher iodine doping content. The specific heat jump (ΔC/γT c) for the optimal composition CuIr2Te3.9I0.1 is approximately 1.46, which is close to the Bardeen–Cooper–Schrieffer value of 1.43, indicating that it is a bulk superconductor. The results of thermodynamic heat capacity measurements under different magnetic fields [C p(T, H)], magnetization M(T, H) and magneto-transport ρ(T, H) measurements further suggest that CuIr2Te4−x I x bulks are type-II superconductors. Finally, an electronic phase diagram for this CuIr2Te4−x I x system has been constructed. The present study provides a suitable material platform for further investigation of the interplay of the CDW and superconductivity.

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 Cu1-xAgxIr2-yZryTe4-z(I/Se)z, [23,32,60,61] but it differs from the CuIr2-x(Ru/Ti)xTe4 and Cu0.5-xZnxIrTe2 systems without reappearance of CDW transition in the high doping range. [21,22,62] 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 Tc and yields the highest Tc 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 Tc where the degradation of Tc 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.…”

“…[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 CuIr2Te4. [22][23][24] Therefore, it is still of interest to explore the path from the layer CuIr2Te4 chalcogenide to the CuIr2S4 spinel by chemical alloying.…”

Negative Chemical Pressure Effect on the Superconductivity and Charge Density Wave of Cu0.5Ir1–xZrxTe2

“…As shown in Figure S2a, the Hall traces show a linear dependence on the perpendicular magnetic field at different selected temperatures from 2–200 K. The nearly identical slope of different samples indicates that the carrier concentration does not show obvious change with increasing Zr doping. Moreover, the carrier density shown in Figure S2b of the Zr-doped samples is comparable to that of undoped Cu 0.5 IrTe 2 . Thus, the Hall results suggest that the carriers are not doped by Zr substitution in this system.…”

“…This shows a clear contrast to the Cu 0.5 Ir 1– x Ru x Te 2 and Cu 0.5 Ir 1– x Ti x Te 2 systems, where the CDW order is quickly suppressed and vanishes in all Ru/Ti-substituted compounds. In addition, in Te-site doping, the CDW order in the Cu 0.5 IrTe 2– x I x system also re-emerges at x ≥ 0.45 . It should be noted that I substituting Te causes the cell parameters to expand, that is, it creates negative chemical pressure .…”

Spatially Separated Superconductivity and Enhanced Charge-Density-Wave Ordering in an IrTe2 Nanoflake

“…The competition, coexistence, or cooperation of various collectively ordered electronic states has been a breeding ground for novel states of matter. , Charge density wave (CDW) order, one of the most studied correlated states, is a periodic modulation of the atoms and conduction electron densities in low-dimensional compounds. , Strong electron–phonon coupling would open a small gap on the Fermi surface and induce a metal–insulator transition. As for superconductivity (SC), the strong electron–phonon interaction leads to condensations of paired electrons within the BCS framework.…”