Effect of uranium deficiency on normal and superconducting properties in unconventional superconductor UTe$_2$

TL;DR

This study investigates how uranium deficiency affects the superconducting and normal properties of UTe$_2$, revealing that near-stoichiometry correlates with superconductivity and specific electronic characteristics.

Contribution

It provides detailed analysis of the relationship between stoichiometry and superconductivity in UTe$_2$, highlighting the importance of precise composition control.

Findings

Superconducting UTe$_2$ is nearly stoichiometric within 1% error.

Non-superconducting samples deviate significantly from ideal composition.

Superconducting samples show a partially gapped density of states in the normal state.

Abstract

Single crystals of the unconventional superconductor UTe$_2$ have been grown in various conditions which result in different superconducting transition temperature as well as normal state properties. Stoichiometry of the samples has been characterized by the single-crystal X-ray crystallography and electron microprobe analyses. Superconducting samples are nearly stoichiometric within an experimental error of about 1 \%, while non-superconducting sample significantly deviates from the ideal composition. The superconducting UTe$_2$ showed that the large density of states was partially gapped in the normal state, while the non-superconducting sample is characterized by the relatively large electronic specific heat as reported previously.