Superconductivity of epsilon-Fe: complete resistive transition

TL;DR

This paper reports the first observation of a complete resistive transition indicating superconductivity in epsilon-iron at high pressure, highlighting its sensitivity to disorder and its nearly ferromagnetic normal state.

Contribution

It provides definitive evidence of superconductivity in epsilon-iron with a complete resistive transition, a significant advancement over previous inconclusive reports.

Findings

Superconductivity observed at 22.2 GPa with T_c just above 2 K

Superconductivity develops only when electronic mean free path exceeds a threshold

Normal state resistivity suggests epsilon-iron is a nearly ferromagnetic metal

Abstract

Last year, iron was reported to become superconducting at temperatures below 2K and pressures between 15 and 30 GPa. The evidence presented was a weak resistivity drop, suppressed by a magnetic field above 0.2 T, and a small Meissner signal. However, a compelling demonstration, such as the occurrence of zero resistance, was lacking. Here we report the measurement of a complete resistive transition at 22.2 GPa with an onset slightly above 2 K in two very pure samples of iron, of different origins. The superconductivity appears unusually sensitive to disorder, developing only when the electronic mean free path is above a threshold value, while the normal state resistivity is characteristic of a nearly ferromagnetic metal.