Doping Driven ($\pi, 0$) Nesting and Magnetic Properties of Fe$_{1+x}$Te Superconductors

TL;DR

This study uses first-principles calculations to explore how doping in Fe$_{1+x}$Te alters its electronic structure and magnetic properties, revealing a new nesting mechanism that supports a similar superconductivity mechanism as in Fe arsenides.

Contribution

It uncovers a doping-induced ($ ext{ extpi}, 0$) nesting in Fe$_{1+x}$Te, providing new insights into its magnetic structure and superconductivity mechanism.

Findings

Doping leads to a ($ extpi, 0$) Fermi surface nesting in Fe$_{1+x}$Te.

Magnetic interactions depend critically on doping levels.

The results reconcile theoretical models with experimental observations.

Abstract

To understand newly discovered superconductivity in Fe--based systems, we investigate electronic structure and magnetic properties of Fe$_{1+x}$Te using first--principles density functional calculations. While the undoped FeTe has the same Fermi surface nested at ($\pi ,\pi $) as in Fe arsenides, doping by $\sim 0.5$ electrons reveals a novel square--type Fermi surface showing a strong ($\pi, 0$) nesting and leading to a different magnetic structure. Our result strongly supports the same mechanism of superconductivity in chalcogenides as in the arsenides, reconciling theory to existing experiments. Calculated magnetic interactions are found to be critically dependent on doping and notably different from the arsenides.