New Lithium-based full Heusler superconductors

There are more than 1000 reported compounds in the full Heusler family and only 35 reveal superconductivity. Here we present details of the synthesis and physical properties (resistivity, magnetization and heat capacity) of the recently reported Li-based ternary intermetallic superconductors LiGa2Ir [1] and LiPd2Ge [2]. The first compound, together with isoelectronic LiGa2Rh, is one of the only two superconductors known in this system with valence electron count (VEC) = 16. The experiments confirm bulk superconductivity with Tc = 2.95 K and suggest that LiGa2Ir is a weak-coupling type-II superconductor (e-p = 0.57, ¬C/¬Tc = 1.4). The second compound (LiPd2Ge) was synthesized together with LiPd2Si and LiPd2Sn. Superconductivity above 1.7 K was found only in LiPd¬2Ge (Tc = 1.96 K) but theoretical studies suggest that LiPd2Si and LiPd2Sn should also reveal superconducting behavior. We propose that the enhanced electron-phonon coupling in LiPd2Ge is due to presence of the soft phonon modes. Surprisingly, LiPd2Ge is a type-I superconductor, which is very rare among ternary intermetallic compounds.

We acknowledge support from the National Science Centre (Poland), grant number: 2017/27/B/ST5/03044 (Gdansk Tech.) and 2017/26/E/ST3/00119 (AGH-UST).

[1] K. Górnicka, G. Kuderowicz, E.M. Carnicom, K. Kutorasiński, B. Wiendlocha, R.J. Cava and T. Klimczuk, Phys. Rev. B, 102, 024507 (2020)
[2] K. Górnicka, G. Kuderowicz, M.J. Winiarski, B. Wiendlocha, and T. Klimczuk, Scientific Reports, 11, 16517 (2021)