Tracing magnetism and pairing in FeTe-based systems

Abstract

Magnetism in the Fe-chalcogenide FeTe, under various modulations, provides important clues with regard to possible precursors to superconductivity. In this study, we monitor the non-superconducting chalcogenide FeTe and follow its transitions under insertion of oxygen, Fe, doping with Se, and vacancies of Fe using spin-polarized band structure methods (utilizing GGA) originating 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. For the most part, the calculated values of magnetic moments agree well with available experimental data prior to superconducting transitions with some of the modulations leading to significant changes in the bicollinear or collinear magnetic moments/arrangements. The total energies of these systems indicate that the collinear-derived structure is the more favorable one prior to a possible superconducting transition. Using the Hubbard model on a 8-site Betts-cluster-based lattice, we show why these systems favor electron or hole pairing under appropriate modulations and could lead to a common understanding of charge and spin pairing in the cuprates, pnictides, and chalcogenides.

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http://link.springer.com.sci-hub.tw/article/10.1007/s10853-012-6608-7