Anatomy of the Band Structure of the Newest Apparent Near-Ambient Superconductor LuH3 –xNx

Abstract

Recently it was claimed that nitrogen-doped lutetium hydride exhibited a near-ambient superconducting transition with a temperature of 294 K at a pressure of only 10 kbar, this pressure being several orders of magnitude lower than previously demonstrated for hydrides under pressure. In this paper, we investigate within DFT + U the electronic structure of both parent lutetium hydride LuH3 and nitrogen doped lutetium hydride LuH2.75N0.25. We calculated corresponding bands, density of states and Fermi surfaces with and without spin-orbit coupling (SOC). It is shown that in the stoichiometric system the Lu-5 d states cross the Fermi level while the H- 1s states make almost no contribution at the Fermi level. However, with nitrogen doping, the N‑ 2p states enter the Fermi level in large quantities and bring together a significant contribution from the H‑ 1s states. The presence of N- 2p and H-1s states at the Fermi level in a doped compound can facilitate the emergence of superconductivity. Surprisingly, SOC splits quite significantly (0.1–0.25 eV) nitrogen bands in LuH2.75N0.25 just below the Fermi level. For instance, nitrogen doping almost doubles the value of DOS at the Fermi level. Simple BCS analysis shows that the nitrogen doping of LuH3 can provide Tc more than 100 K and even increase it with further hole doping.