Anatomy of the band structure of the newest apparent near-ambient superconductor LuH$_{3-x}$N$_x$

TL;DR

This study investigates the electronic structure of nitrogen-doped lutetium hydride using DFT+U, revealing how doping modifies states at the Fermi level and potentially enhances superconductivity with T_c exceeding 100K.

Contribution

It provides a detailed electronic structure analysis of nitrogen-doped lutetium hydride, highlighting the role of N-2p and H-1s states in promoting superconductivity, which was not previously understood.

Findings

Nitrogen doping introduces N-2p states at the Fermi level.

Doping nearly doubles the density of states at the Fermi level.

Simple BCS analysis suggests T_c can exceed 100K with doping.

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 LuH$_3$ and nitrogen doped lutetium hydride LuH$_{2.75}$N$_{0.25}$. We calculated corresponding bands, density of states and Fermi surfaces. It is shown that in the stoichiometric system the Lu-5d 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. For instance, nitrogen doping almost doubles the value of DOS at the Fermi level. Simple BCS analysis shows that the nitrogen doping of LuH$_3$ can provide T$_c$ more than 100K and even increase it with further hole doping.