We report the discovery of superconductivity in a series of
noncentrosymmetric compounds La4βTX (T = Ru, Rh, Ir; X = Al, In), which
have a cubic crystal structure with space group F4Λ3m. La4βRuAl,
La4βRhAl, La4βIrAl, La4βRuIn and La4βIrIn exhibit bulk superconducting
transitions with critical temperatures Tcβ of 1.77 K, 3.05 K, 1.54 K, 0.58 K
and 0.93 K, respectively. The specific heat of the La4βTAl compounds are
consistent with an s-wave model with a fully open superconducting gap. In all
cases, the upper critical fields are well described by the
Werthamer-Helfand-Hohenberg model, and the values are well below the Pauli
limit, indicating that orbital limiting is the dominant pair-breaking
mechanism. Density functional theory (DFT) calculations reveal that the degree
of band splitting by the antisymmetric spin-orbit coupling (ASOC) shows
considerable variation between the different compounds. This indicates that the
strength of the ASOC is highly tunable across this series of superconductors,
suggesting that these are good candidates for examining the relationship
between the ASOC and superconducting properties in noncentrosymmetric
superconductors.Comment: 10 pages, 7 figure