Theory of Infrared Hall Conductivity Based on the Fermi Liquid Theory : Analysis of High-T_c Superconductors(Condensed matter: electronic structure and electrical, magnetic, and optical properties)

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We study optical Hall conductivity for high-T_c superconductors on the basis of microscopic Fermi liquid theory. Current vertex corrections (CVCs) are correctly taken into account to satisfy the conservation laws, and are performed for the first time for optical conductivities based on the fluctuation-exchange (FLEX) approximation. We find that (I) the CVC emphasizes the ω-dependence of σ_<xy>(ω) significantly when the antiferromagnetic (AF) fluctuations are strong. For this reason, the relation σ_<xy>(ω)〜{σ_<xx>(ω)}^2, which is satisfied in the extended Drude model given by the relaxation time approximation (RTA), is completely violated for a wide range of frequencies. Consequently, (II) the optical Hall coefficient R_H(ω) strongly depends on ω below infrared frequencies, which is consistent with experimental observations. Interestingly, although σ_<xx>(ω) does not follow a simple Drude form due to theω-dependence of the relaxation time τ, θ_H(ω) and σ_<xy>(ω) follow approximate simple Drude forms since theω-dependences of τ and CVC almost cancel each other out. In conclusion, anomalous optical transport phenomena in high-T_c superconductors, which had been frequently assumed to be as evidence of the breakdown of the Fermi liquid state, can be well explained in terms of the nearly AF Fermi liquid once the CVC is taken into account.
社団法人日本物理学会の論文
2007-07-15