Observation of superconductivity in the intermetallic compound β-IrSn₄

Abstract

Low-temperature dc-magnetization, ac electrical resistivity and specific heat measurements were performed on single crystals of the intermetallic compound β-IrSn4. The compound crystallizes in the tetragonal MoSn4-type structure (space group I41/acd) and exhibits superconductivity below Tc = 0.9 ± 0.05 K. Further, the magnitude of the ratios ΔCp/(γnkBTc) = 1.29, 2Δ/(kBTc) = 3.55 and of the electron-phonon coupling λ[overline](e-ph) = 0.5 imply that superconductivity in β-IrSn4 can be ascribed to a s-wave weak coupling regime. We determined crucial thermodynamic characteristics of the superconducting state. It turned out that depending on the assumption of either a spherical or non-spherical Fermi surface, the superconductivity can be ascribed to either a type-I and type-II/1 or type-II in clean limit, respectively. However, the behavior of the upper critical field and the anisotropic crystalline structure of the studied compound provide strong support to the type-II superconductivity. In the normal state the resistivity exhibits a prominent quadratic temperature dependence, which together with a large Kadowaki-Woods ratio and with the enhanced effective mass indicate that the electrons in β-IrSn4 are strongly correlated.

Type-I superconductivity in KBi2single crystals

“…Based on this, two different assumptions can be made: either (i) KBi 2 is a type-II SC that the upper critical field H c2 is very small and close to the lower critical field H c1 ; or (ii) KBi 2 is a type-I SC and the departure from the ideal step-like transition at critical field may be attributed to a strong pinning of domain walls in the intermediate state or to unclear demagnetization. 23 For the latter case, the critical field H c is defined as the field where the sample enters to the normal state (M (H) = 0). On the other hand, when temperature decreases, the critical field shifts to higher field.…”

Electronic band structure and superconducting properties of SnAs

“…Figure 8 shows isothermal magnetization loop M (H) at T = 2 K. The shape of the curve is nearly typical for type-I superconductor, however it reveals a small hysteresis. Such hysteresis is observed in other compounds considered to be type-I superconductors and, generally, is associated with sample shape effects, domain or grain walls etc [29,[31][32][33][34]. Temperature dependences of the specific heat in various magnetic fields are shown on Fig.…”

“…This effect is observed for mixed state of type-I superconductors or in type-II superconductors with close H c1 and H c2 values. considered to be type-I superconductors and, generally, is associated with sample shape effects, domain or grain walls etc [29,[31][32][33][34]. Temperature dependences of the specific heat in various magnetic fields are shown on Fig.…”

Ab initio investigation of electronic structure and optical properties of IrSn4

“…It was surprising enough that superconductivity in the β-IrSn 4 phase was observed by Tran et al 7 Based on experimental data, the authors suggested that the presence of superconductivity in β-IrSn 4 is due to a weak electron–phonon pairing, even if the possible existence of d-electrons favors strong correlation. 7 The discovery of superconductivity in β-IrSn 4 invites further investigation, not only due to the fact that strong correlations are often the origin of many interesting physical phenomena in materials, such as metal–insulator transitions, magnetic ordering, and superconductivity, 8,9 but also owing to the need to answer some crucial questions, e.g. : (i) how does the strong electron correlation affect the superconductivity of β-IrSn 4 ?…”