Superconducting and topological properties of compound Lu$_4$H$_7$N

TL;DR

This study predicts the superconducting and topological properties of Lu4H7N using first-principles calculations, revealing potential for high Tc under pressure and topological surface states, thus guiding future topological superconductor discovery.

Contribution

It proposes a stable structure for Lu4H7N, analyzes its superconducting Tc, topological features, and effects of electron doping, providing new insights into Lu-H-N compounds.

Findings

Tc of 1.044 K at ambient pressure

Tc enhanced to 11.721 K at 150 GPa

Presence of nontrivial Z2 topological surface states

Abstract

A recent experiment has reported a nitrogen-doped lutetium hydride acheving a remarkable Tc of 294 K at just 1 GPa, significantly reducing the required pressure for obtaining room temperature superconductivity. However, subsequent experimental and theoretical investigations have encountered difficulties in replicating these results, leaving the structure of this Lu-H-N compound shrouded in uncertainty. Here, we propose a stable structure for Lu$_4$H$_7$N employing first-principles calculations. Our calculations reveal that Lu$_4$H$_7$N has a Tc of 1.044 K, which can be substantially enhanced to 11.721 K at 150 GPa, due to the increasing electron-phonon coupling (EPC). Notably, we delve into the nontrivial Z2 band topology of Lu$_4$H$_7$N, featuring discernible surface states near the Fermi level, and we explore its spin Hall conductivity characteristics. Furthermore, we find that the electron doping can enhance the EPC strength and Tc of Lu$_4$H$_7$N, such as the Lu$_4$H$_7$O structure we predict simulating electron doping for Lu$_4$H$_7$N with an impressive Tc of 3.837 K. This work demonstrates the coexistence of superconducting and topological properties in a Lu-H-N system compound, which holds the promise of guiding the search for novel topological superconducting materials.