Structure and physical properties of the noncentrosymmetric superconductor Mo3 Al2 C

We have synthesized polycrystalline samples of the noncentrosymmetric superconductor Mo3 Al2 C by arc and RF melting, measured its transport, magnetic and thermodynamic properties, and computed its band structure. Experimental results indicate a bulk superconducting transition at Tc ∼9.2 K while the density of states at the Fermi surface is found to be dominated by Mod orbitals. Using the measured values for the lower critical field Hc1, upper critical field Hc2, and the specific heat C, we estimated the thermodynamic critical field Hc(0), coherence length ξ (0), penetration depth λ (0), and the Ginzburg-Landau parameter κ (0). The specific-heat jump at Tc, ΔC/γ Tc =2.14, suggests that Mo3 Al 2 C is moderately to strongly coupled, consistent with the fast opening of the gap, as evidenced by the rapid release of entropy below Tc from our electronic specific-heat measurements. Above 2 K the electronic specific heat exhibits the power-law behavior, suggesting that synthesis of single crystals and measurements at lower temperature are needed to establish whether the gap is anisotropic. The estimated value of the upper critical field H c2 (0) is close to the calculated Pauli limit, therefore further studies are needed to determine whether the absence of an inversion center results in a significant admixture of the triplet component of the order parameter. © 2010 The American Physical Society