Inverse Iron Isotope Effect on the transition temperature of the (Ba,K)Fe2As2 superconductor

TL;DR

This study demonstrates an inverse iron isotope effect in (Ba,K)Fe2As2 superconductors, where heavier isotopes lead to higher transition temperatures, suggesting an unconventional pairing mechanism.

Contribution

First experimental evidence of inverse isotope effect in high-Tc superconductors, highlighting a potential exotic coupling mechanism.

Findings

Heavier Fe isotopes correlate with higher Tc.

Inverse isotope effect observed consistently across measurements.

Suggests unconventional superconducting pairing mechanism.

Abstract

We report that (Ba,K)Fe2As2 superconductor (a transition temperature, Tc = 38 K) shows inverse Iron isotope effect (-0.18) (the sample including the larger atomic weight of Fe depicts higher Tc). Measurements of both temperature dependent magnetization and resistivity reveal a clear inverse shift by systematic studies on Tc using three types of Fe-isotopes (Fe-54, natural Fe and Fe-57). This indicates the first evidence of the inverse isotope effect in high-Tc superconductors. This atomic mass dependence on Tc implies the exotic coupling mechanism.