Oxygen-annealing effects on superconductivity in polycrystalline Fe1-xTe1-ySey

TL;DR

This study shows that oxygen annealing removes interstitial iron in Fe1-xTe1-ySey, inducing superconductivity up to 14 K, with the process being irreversible and linked to iron oxide formation.

Contribution

It demonstrates that oxygen annealing enhances superconductivity in Fe1-xTe1-ySey by removing interstitial iron, a novel approach for tuning iron chalcogenide properties.

Findings

Oxygen annealing induces superconductivity in non-superconducting samples.

Superconducting transition temperature reaches up to 14 K.

Iron oxides form during annealing, indicating iron removal.

Abstract

Superconductivity in anti-PbO-type iron chalcogenides Fe1-xTe1-ySey (x = 0, 0.1, y = 0.1 0.4) depends on the amount (x) of interstitial iron atoms located between the FeTe1-ySey layers. Non-superconducting samples of nominal Fe1.1Te1-ySey convert to superconductors with critical temperatures up to 14 K after annealing at 300{\deg}C in an oxygen atmosphere. The process is irreversible upon subsequent hydrogen annealing. Magnetic measurements are consistent with the formation of iron oxides suggesting that oxygen annealing preferably extracts interstitial iron from Fe1-xTe1-ySey which interfere with superconductivity.