Absence of superconductivity in electron-doped chromium pnictides ThCrAsN$_{1-x}$O$_x$

TL;DR

This study synthesized and characterized ThCrAsN and its oxygen-doped variants, finding no superconductivity above 30 mK despite heavy electron doping, and revealing their magnetic and electronic properties differ from iron-based superconductors.

Contribution

It provides experimental and theoretical insights into the magnetic and electronic properties of electron-doped chromium pnictides, challenging assumptions about their potential for superconductivity.

Findings

All samples show metallic conduction without superconductivity above 30 mK.

Magnetic structure is G-type antiferromagnetic.

Heavy electron doping does not significantly alter Cr--Cr interactions.

Abstract

Theoretical studies predicted possible superconductivity in electron-doped chromium pnictides isostructural to their iron counterparts. Here, we report the synthesis and characterization of a new ZrCuSiAs-type Cr-based compound ThCrAsN, as well as its oxygen-doped variants. All samples of ThCrAsN$_{1-x}$O$_x$ show metallic conduction, but no superconductivity is observed above 30 mK even though the oxygen substitution reaches 75\%. The magnetic structure of ThCrAsN is determined to be G-type antiferromagnetic by magnetization measurements and first-principles calculations jointly. The calculations also indicate that the in-plane Cr--Cr direct interaction of ThCrAsN is robust against the heavy electron doping. The calculated density of states of the orbital occupations of Cr for ThCrAs(N,O) is strongly spin-polarized. Our results suggest the similarities between chromium pnictides and iron-based superconductors shouldn't be overestimated.