Hunt for topological odd-parity superconductivity in locally noncentrosymmetric heavy-fermion systems

Topological superconductors represent a fascinating, long-sought quantum state of matter, where the unconventional pairing symmetry can give rise to exotic quasiparticles living at the surfaces, edges, or inside vortex cores – so-called Majorana zero modes [1, 2]. Ce- and U-containing materials, in which conduction electrons interact strongly with localized f states, are considered prime candidates for realizing topological superconductivity. In my talk, I will focus on our recent efforts, guided by simple structural design principles, to systematically screen for locally noncentrosymmetric heavy-fermion compounds with the desired traits for odd-parity superconductivity. I will present thermodynamic and electrical transport studies down to dilution-fridge temperatures of selective candidates based on XYZ₂ (X = Ce or U, Y being a group 8 to 11 transition metal and Z = Si or Ge) with the locally noncentrosymmetric CeNiSi₂ structure (Cmcm). Chemical pressure and band filling tune the ground states of these systems from magnetic to superconducting to non-magnetic behavior, offering a rich platform for exploring unconventional superconductivity.

 

[1] M. Sato & Y. Ando,  Reports on Progress in Physics 80, 076501 (2017)

[2] C. Nayak et al., Reviews of Modern Physics 80, 1083-1159 (2008)