Temperature dependence of NMR Knight shift in pnictides: proximity to a van Hove singularity

Abstract

The unconventional temperature variation of the Knight shift (static spin susceptibility) that has been observed in Fe-based superconductors AFe${}_2$As${}_2$ (A = K, Rb, Cs) is explained in terms of proximity to a van Hove singularity. Using the Hubbard model we show that when the Fermi energy is in the vicinity of a van Hove singularity, a downturn in spin susceptibility occurs as the temperature is lowered. This behavior is characterized by a temperature, $T^{\ast }$, which is determined by the difference in energy between the Fermi level and the van Hove singularity. When vertex corrections are taken into account in a dynamical mean-field approximation, the effect of correlations amplifies the relative drop in the Knight shift and moves $T^{\ast }$ to lower temperatures.

arXiv commentLatex, 4 figures, 4 pages

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Cited by in corpus (2)

• Normal state ${}^{17}$O NMR studies of Sr${}_2$RuO${}_4$ under uniaxial stress
• Van Hove singularities, chemical pressure and phonons: an angle-resolved photoemission study of KFe${}_2$As${}_2$ and CsFe${}_2$As${}_2$