K Haule and G Kotliar 2009 New J. Phys. 11 025021 doi:10.1088/1367-2630/11/2/025021
Coherence–incoherence crossover in the normal state of iron oxypnictides and importance of Hund's rule coupling
Focus on Iron-Based SuperconductorsK Haule1 and G Kotliar
Show affiliationsPart of Focus on Iron-Based Superconductors
A new class of high-temperature superconductors based on iron and arsenic was recently discovered (Kamihara et al 2008 J. Am. Chem. Soc. 130 3296), with the superconducting transition temperature as high as 55 K (Ren et al 2008 Chin. Phys. Lett. 25 2215). Here we show, using microscopic theory, that the normal state of the iron pnictides at high temperatures is highly anomalous, displaying a very enhanced magnetic susceptibility and a linear temperature dependence of the resistivity. Below a coherence scale T*, the resistivity sharply drops and susceptibility crosses over to Pauli-like temperature dependence. Remarkably, the coherence–incoherence crossover temperature is a very strong function of the strength of Hund's rule coupling JHund. On the basis of the normal state properties, we estimate JHund to be ~0.35 eV. In the atomic limit, this value of JHund leads to the critical ratio of the exchange constants J1/J2~2. While normal state incoherence is common to all strongly correlated superconductors, the mechanism for emergence of the incoherent state in iron oxypnictides is unique due to its multiorbital electronic structure.
- PACS
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74.25.Fy Transport properties (electric and thermal conductivity, thermoelectric effects, etc.)
- Subjects
- Dates
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Issue 2 (February 2009)
Received 16 December 2008
Published 27 February 2009
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Coherence–incoherence crossover in the normal state of iron oxypnictides and importance of Hund's rule coupling
K Haule and G Kotliar 2009 New J. Phys. 11 025021
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