Superconducting and normal state properties of the layered boride OsB2

Abstract

OsB_2 crystallizes in an orthorhombic structure (Pmmn) which contains alternate boron and osmium layers stacked along the c-axis. The boron layers consist of puckered hexagons as opposed to the flat graphite-like boron layers in MgB_2. OsB_2 is reported to become superconducting below 2.1 K. We report results of the dynamic and static magnetic susceptibility, electrical resistivity, Hall effect, heat capacity and penetration depth measurements on arc-melted polycrystalline samples of OsB_2 to characterize its superconducting and normal state properties. These measurements confirmed that OsB_2 becomes a bulk superconductor below T_ c = 2.1 K. Our results indicate that OsB_2 is a moderate-coupling Type-II superconductor with an electron-phonon coupling constant λ_{ep} \approx 0.4 to 0.5, a small Ginzburg-Landau parameter κ\sim 1 to 2 and an upper critical magnetic field H_{c2}(0.5 K) \sim 420 Oe for an unannealed sample and H_{c2}(1 K) \sim 330 Oe for an annealed sample. The temperature dependence of the superfluid density n_{s}(T) for the unannealed sample is consistent with an s-wave superconductor with a slightly enhanced zero temperature gap Δ(0) = 1.9 k_{B}T_c and a zero temperature London penetration depth λ(0) = 0.38(2) μm. The n_{s}(T) data for the annealed sample shows deviations from the predictions of the single-band s-wave BCS model. The magnetic, transport and thermal properties in the normal state of isostructural and isoelectronic RuB_2, which is reported to become superconducting below 1.6 K, are also reported.

16 pages, 23 figures, 1 table; v2: New data and analysis on an annealed sample of OsB2

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• Multi-gap superconductivity and Shubnikov-de Haas oscillations in single crystals of the layered boride OsB_2
• Magnetic, Thermal, and Transport Properties of Layered Arsenides BaRu2As2 and SrRu2As2
• Low-temperature properties of single-crystal CrB${}_2$
• Role of electronic correlations in the Kagome lattice superconductor LaRh${}_3$B${}_2$
• Possible multigap Type-I superconductivity in the layered Boride RuB${}_2$
• Discovery of superconductivity in technetium-borides at moderate pressures
• Fluctuations in superconducting rings with two order parameters
• Electron-phonon coupling and superconductivity in LiB${}_{1+x}$C${}_{1-x}$
• Spectroscopic signature of two superconducting gaps and their unusual field dependence in RuB${}_2$
• Machine-learning Guided Search for Phonon-mediated Superconductivity in Boron and Carbon Compounds