Investigation of normal and superconducting states in noncentrosymmetric Re24Ti5.

We report a detailed characterization of the noncentrosymmetric superconductor Re24Ti5 using powder x-ray diffraction (XRD), magnetic susceptibility, electrical resistivity, thermal conductivity, Seebeck coefficient, and specific heat measurements. Rietveld refinement of powder XRD data confirms that Re24Ti5 crystallizes in the α-Mn structure. All measured quantities demonstrate a bulk superconducting transition at Tc = 5:8 K. Our low-temperature specific heat data measured down to 0.5 K yield a Sommerfeld coefficient γ = 111:8 mJ mol-1 K-2, which implies a high density of states at the Fermi level. Moreover, the electronic specific heat in the superconducting state was found to obey a typical s-wave expression, revealing a single gap Δ/kB = 10:6 K. This value gives a ratio of 2Δ/kBTc D 3:68, higher than the value of 3.5 predicted from BCS theory. On this basis, we conclude that the noncentrosymmetric Re24Ti5 compound can be characterized as a moderately coupled BCS-type superconductor. Furthermore, the obtained parameters from the present study of Re24Ti5 were compared to those of the isostructural compound Re23:8Nb5:2, indicating the similarity between both systems. [ABSTRACT FROM AUTHOR]