Possibility of Skyrmion Superconductivity in Doped Antiferromagnet K${}_2$Fe${}_4$Se${}_5$

Abstract

Intercalated Fe chalcogenide K${}_2$Fe${}_4$Se${}_5$ family exhibits high Tc ($\sim$ 30 K) superconductivity and spin-8 high T${}_{\mathrm{N}}$ ($\sim$ 560 K) antiferromagnetism (AFM). We present a model Hamiltonian and suggest \textit{Skyrmion superconductivity}. A doped electron creates an orbitally non degenerate S=7\half state in a F${}_4$Se${}_9$ cluster and moves in a single correlated band, exchange coupled to a robust S=8 AFM order. Skyrmion, a topological excitation of 2 dimensional AFM order acquires an \textit{induced charge -2e} through a quantum anomaly and becomes a Cooper pair. Superconductivity emerges for a range of doping. Fluctuating superconductivity, arising from preformed Cooper pairs (stable Skyrmions), around room temperatures is predicted. We offer hope for higher Tc's in large-S Mott insulators.

4 pages, 4 figures

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