On the role of chalcogen vapor annealing in inducing bulk superconductivity in Fe$_{1+y}$Te$_{1-x}$Se$_{x}$

TL;DR

This study investigates how Te vapor annealing induces bulk superconductivity in Fe$_{1+y}$Te$_{1-x}$Se$_{x}$ by forming FeTe complexes that suppress magnetic moments, with implications for enhancing superconducting properties.

Contribution

It reveals that Te vapor annealing primarily quenches magnetic moments by forming FeTe complexes, providing a detailed mechanism for vapor-induced superconductivity in these materials.

Findings

Te vapor forms FeTe complexes that suppress magnetic moments.

Remaining FeTe complexes still hinder superconductivity.

Removing FeTe complexes could further enhance superconductivity.

Abstract

Recent investigations have shown that Fe$_{1+y}$Te$_{1-x}$Se$_{x}$ can be made superconducting by annealing it in Se and O vapors. The current lore is that these chalcogen vapors induce superconductivity by removing the magnetic excess Fe atoms. To investigate this phenomenon we performed a combination of magnetic susceptibility, specific heat and transport measurements together with scanning tunneling microscopy and spectroscopy and density functional theory calculations on Fe$_{1+y}$Te$_{1-x}$Se$_{x}$ treated with Te vapor. We conclude that the main role of the Te vapor is to quench the magnetic moments of the excess Fe atoms by forming FeTe$_{m}$ (m $\geq$ 1) complexes. We show that the remaining FeTe$_{m}$ complexes are still damaging to the superconductivity and therefore that their removal potentially could further improve superconductive properties in these compounds.