Unconventional isotope effect on transition temperature in BiS2-based superconductor Bi4O4S3

TL;DR

This study investigates the sulfur isotope effect on the superconducting transition temperature in Bi4O4S3, revealing an unconventional pairing mechanism due to the negligible isotope effect observed.

Contribution

It provides the first experimental analysis of isotope effects in BiS2-based superconductors, indicating unconventional pairing states.

Findings

No clear correlation between Tc and isotope mass.

Isotope exponent (aS) estimated as -0.1 < aS < 0.1.

Results suggest unconventional pairing mechanisms.

Abstract

We report the sulfur isotope effect on transition temperature in a BiS2-based superconductor Bi4O4S3. Polycrystalline samples of Bi4O4S3 were prepared using 32S and 34S isotope chemicals. From magnetization analyses, the isotope exponent (aS) was estimated as -0.1 < aS < 0.1. Although the Tc estimated from electrical resistivity was scattered as compared to those estimated from the magnetization, we observed no clear correlation between Tc and the isotope mass. The present results suggest that unconventional paring states are essential in Bi4O4S3.