Tracing magnetism and pairing in FeTe-based systems

TL;DR

This study investigates how magnetism and superconductivity interact in FeTe-based systems by examining magnetic transitions under various modifications using computational methods, providing insights into pairing mechanisms across different superconductors.

Contribution

It combines spin-polarized band structure calculations with Hubbard model analysis to elucidate magnetic structures and pairing tendencies in FeTe systems, linking them to broader superconducting phenomena.

Findings

Oxygen insertion significantly alters magnetic moments.

The collinear magnetic structure is energetically favored before superconductivity.

The Hubbard model reveals why certain magnetic arrangements promote pairing.

Abstract

In order to examine the interplay between magnetism and superconductivity, we monitor the non- superconducting chalcogenide FeTe and follow its transitions under insertion of oxygen, doping with Se and vacancies of Fe using spin-polarized band structure methods (LSDA with GGA) starting from the collinear and bicollinear magnetic arrangements. We use a supercell of Fe8Te8 as our starting point so that it can capture local changes in magnetic moments. The calculated values of magnetic moments agree well with available experimental data while oxygen insertions lead to significant changes in the bicollinear or collinear magnetic moments. The total energies of these systems indicate that the collinear-derived structure is the more favorable one prior to a possible superconducting transition. Using a 8-site Betts-cluster-based lattice and the Hubbard model, we show why this structure favors electron or hole pairing and provides clues to a common understanding of charge and spin pairing in the cuprates, pnictides and chalcogenides.