CeIr₃: superconductivity in a phase based on tetragonally close packed clusters

Abstract

We present the crystallographic analysis, superconducting and spectroscopic characterization, and theoretical modeling of CeIr3. Lattice parameters a = 5.2945(1) Å and c = 26.219(1) Å are found for the R-3m symmetry crystal structure, which are close to the literature values. CeIr3 is a moderate type-II superconductor (κGL = 17, λe–p = 0.65) below 2.5 K. Ce ions exhibit a strongly intermediate valence character as evidenced by x-ray photoelectron spectroscopy. The normal state magnetic susceptibility is weakly temperature dependent and follows the inter-configuration fluctuation model with a singlet Ce−4 f 0 ground state. Theoretical calculations support a non-magnetic ground state of the system and reveal that Ir−5d states are dominant at the Fermi level.

Single Crystal Growth and Anisotropy of the Upper Critical Field of CeIr3

“…Figure 1(c) shows the temperature dependence of electrical resistivity ρ for the electrical current J || a-axis at zero field. ρ(T ) decreases with decreasing temperature and shows a slightly convex curvature, as reported previously [12,14]. The electrical resistivity suddenly drops to zero, and the transition temperature T c was determined to be 3.4 K using the criteria of the midpoint of the resistivity drop.…”

“…By analyzing the superconducting transition temperature in La-and Th-doped system, the valence number has been estimated to be 3.6 in CeIr 3 [13]. Lately, the strongly intermediate valence character of CeIr 3 has also been reported by X-ray photoelectron spectroscopy [14]. It appears that the valence fluctuations in CeIr 3 may be related to its superconducting properties.…”

NbIr2B2 and TaIr2B2 – New Low Symmetry Noncentrosymmetric Superconductors with Strong Spin–Orbit Coupling

“…Having the calculated Debye temperature Θ D , the electron–phonon constant λ e–p , a dimensionless number that describes the coupling between the electron and the phonon, can be calculated from the inverted McMillan formula [ 24 ] where µ * is the Coulomb pseudopotential parameter having typical material specific values in the range 0.1 ≤ µ * ≤ 0.15, where 0.13 is typically used for intermetallic superconductors. [ 9,25–27 ] The constant λ e–p = 0.74 for NbIr 2 B 2 and λ e–p = 0.70 for TaIr 2 B 2 , suggesting that both compounds are moderately or strongly coupled superconductors.…”

“…where μ* is the Coulomb pseudopotential parameter having typical material specific values in the range 0.1 ≤ μ* ≤ 0.15, where 0.13 is typically used for intermetallic superconductors. [9,[25][26][27] The constant λ e-p = 0.74 for NbIr 2 B 2 and λ e-p = 0.70 for TaIr 2 B 2 , suggesting that both compounds are moderately or strongly coupled superconductors. The temperature dependence of the electronic specific heat (C el ) below T c for NbIr 2 B 2 is shown in Figure 3c.…”

Electronic structure of CeIr3 superconductor: DMFT studies

“…As shown in previous works [8,9], CeIr 3 is a nonmagnetic, type-II superconductor with T c =2.5 K and moderately-strong electron-phonon coupling (EPC), with a generally conventional BCS-type behavior seen e.g. in the heat capacity measurements [8]. The EPC constant λ ep , estimated based on the T c and McMillan formula [10], is λ ep = 0.65.…”