Interplay of structure, magnetism, and superconductivity in Se substituted iron telluride with excess Fe

TL;DR

This study explores how selenium substitution affects the phase diagram, magnetism, and superconductivity in Fe$_{1+y}$Te with excess Fe, revealing the emergence of superconductivity at higher Se levels despite high Fe content.

Contribution

It provides a detailed phase diagram showing the interplay of structure, magnetism, and superconductivity in Se-substituted Fe telluride with excess Fe.

Findings

Superconductivity appears for Se concentrations x ≥ 0.1.

Se substitution causes the two magneto-structural transitions to merge.

Superconductivity emerges despite high Fe excess.

Abstract

We investigated the evolution of the temperature-composition phase diagram of Fe$_{1+y}$Te upon Se substitution. In particular, the effect of Se substitution on the two-step, coupled magneto-structural transition in Fe$_{1+y}$Te single crystals is investigated. To this end, the nominal Fe excess was kept at $y$ = 0.12. For low Se concentrations, the two magneto-structural transitions displayed a tendency to merge. In spite of the high Fe-content, superconductivity emerges for Se concentrations, $x \geq$ 0.1. We present a temperature-composition phase diagram to demonstrate the interplay of structure, magnetism, and superconductivity in these ternary Fe chalcogenides.