Article

# Nonanalytic Spin Susceptibility of a Fermi Liquid: The Case of Fe-Based Pnictides

Max-Planck-Institut für Physik komplexer Systeme, D-01187 Dresden, Germany.
(Impact Factor: 7.51). 07/2009; 102(23):236403. DOI: 10.1103/PhysRevLett.102.236403
Source: PubMed

ABSTRACT We propose an explanation of the peculiar linear temperature dependence of the uniform spin susceptibility chi(T) in ferropnictides. We argue that the linear in T term appears to be due to the nonanalytic temperature dependence of chi(T) in a two-dimensional Fermi liquid. We show that the prefactor of the T term is expressed via the square of the spin-density-wave (SDW) amplitude connecting nested hole and electron pockets. Because of an incipient SDW instability, this amplitude is large, which, along with a small value of the Fermi energy, makes the T dependence of chi(T) strong. We demonstrate that this mechanism is in quantitative agreement with the experiment.

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Available from: Dmitri V. Efremov, Sep 25, 2015
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• "The former saturates below 50 − 60K, as the nematic order parameter tends to a constant [25]. At the same time the anisotropic part of the transverse susceptibility changes due to non-Fermi liquid effects caused by the enhanced spin fluctuations [28], leading to the observed decrease in ∆K a in the normal state. The issue that remains open from the NMR data is the precise pattern of orbital ordering that is formed. "
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Nature Material 02/2015; 14:210. DOI:10.1038/nmat4138 · 36.50 Impact Factor
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ABSTRACT: We report the Hall resistivity, rho(xy), of polycrystalline SmFeAsO1-xFx for four different fluorine concentrations from the onset of superconductivity through the collapse of the structural phase transition. For the two more highly doped samples, rho(xy) is linear in magnetic field up to 50 T with only weak temperature dependence, reminiscent of a simple Fermi liquid. For the lightly doped samples with x < 0.15, we find a low temperature regime characterized as rho(xy) (H) being both nonlinear in magnetic field and strongly temperature-dependent even though the Hall angle is small. The onset temperature for this nonlinear regime is in the vicinity of the structural phase (SPT)/magnetic ordering (MO) transitions. The temperature dependence of the Hall resistivity is consistent with a thermal activation of carriers across an energy gap. The evolution of the energy gap with doping is reported.
Journal of Physics Condensed Matter 10/2009; 21(41). DOI:10.1088/0953-8984/21/41/412201 · 2.35 Impact Factor