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arXiv · 1207.3033

Strong electronic correlations from Hund's coupling

Antoine Georges·Luca de' Medici·Jernej Mravlje
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Abstract

Strong electronic correlations are often associated with the proximity of a Mott insulating state. In recent years however, it has become increasingly clear that the Hund's rule coupling (intra-atomic exchange) is responsible for strong correlations in multi-orbital metallic materials which are not close to a Mott insulator. Hund's coupling has two effects: it influences the energetics of the Mott gap and strongly suppresses the coherence scale for the formation of a Fermi-liquid. A global picture has emerged recently, which emphasizes the importance of the average occupancy of the shell as a control parameter. The most dramatic effects occur away from half-filling or single occupancy. The theoretical understanding and physical properties of these `Hund's metals' are reviewed, together with the relevance of this concept to transition-metal oxides of the 3d, and especially 4d series (such as ruthenates), as well as to the iron-based superconductors (iron pnictides and chalcogenides).

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Antoine Georges, Luca de' Medici, Jernej Mravlje. 2012-07-12. Strong electronic correlations from Hund's coupling. https://doi.org/10.1146/annurev-conmatphys-020911-125045

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