Structure and physical properties of the noncentrosymmetric superconductorMo3Al2C

Abstract

We have synthesized polycrystalline samples of the noncentrosymmetric superconductor Mo 3 Al 2 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 T c ~ 9.2 K, while the density of states at the Fermi surface is found to be dominated by Mo d-orbitals. Using the measured values for the lower critical field H c1 , upper critical field H c2 , and the specific heat C, we estimated the thermodynamic critical field H c (0), coherence length ξ(0), penetration depth λ(0), and the Ginzburg-Landau parameter κ(0). The specific heat jump at T c , ΔC/γT c = 2.14, suggests that Mo 3 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 T c from our electronic specific heat measurements. Above 2K 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.

Superconducting properties of noncentrosymmetric superconductorCaIrSi3investigated by muon spin relaxation and rotation

“…We note that conventional superconductivity in NCSCs is not uncommon [50][51][52][53] , despite the theoretical possibility of exotic behavior. It has been suggested that the presence of substantial electronic correlations is a necessary ingredient for appreciable spin-triplet pairing in NCSCs 54 , which is one possible explanation for the apparent lack of unconventional behavior in the uncorrelated compound CaIrSi 3 .…”

Superconductivity in noncentrosymmetric YPtBi under pressure

“…5 , CeIrSi 3 (T c = 1.6 K under pressure) 6 , Li 2 Pt 3 B (T c = 2.6 K) 7 and Mo 3 Al 2 C (T c = 9.2 K) 8,9 . For several NCS SCs solid evidence for an odd-parity component in the SC order parameter has been extracted from critical magnetic fields exceeding the spin-singlet Pauli paramagnetic limit and/or line or point nodes in the SC gap function…”

Multigap superconductivity in chiral noncentrosymmetric TaRh2B2

“…Li 2 Pd 3 B is an s-wave superconductor, while the stronger ASOC in Li 2 Pt 3 B enhances the triplet component, producing line nodes in the gap, as revealed by the linear temperature dependence of the magnetic penetration depth λ(T ) at low T [11,12]. Mo 3 Al 2 C (NCS chiral space group P 4 1 32) is a strongly coupled superconductor with a T c of 9 K. NMR and electronic heat capacity data, along with a pressure-enhanced T c , suggest Mo 3 Al 2 C has a nodal gap with singlet-triplet mixing [13,14].…”