Role of 4f states in superconducting nickelate

For a long time, condensed matter physicists have a question whether there may be nickelates that can host a cuprate-type superconductor. Very recently, NdNiO₂ by 20%-Sr doping leads to superconducting up to T_c=15 K, while another most promising candidate LaNiO₂ has never been superconducting. These discovery has been rejuvenated the long standing issue. In this presentation, we will focus on a primary distinction between NdNiO₂ and LaNiO_2. An obvious difference is that La³⁺ is closed shell and nonmagnetic, while Nd³⁺ with Hund’ rule ground state S=3/2, L=6, J=9/2 has a Curie-Weiss moment of about 3μ_B. Our results indicate that this magnetic interaction in Nd_0.8Sr_0.2NiO₂ causes spin-disorder broadening of the Γ-centered Nd-driven electron Fermi surfaces and should be included in models of normal and superconducting states of Nd_0.8Sr_0.2NiO₂