Nernst Coefficient in High-Tc Superconductors: the Role of Superconducting Fluctuations

In hole-doped high-Tc cuprates, the Nernst coefficient (ν) as well as the magnetoresistance (Δρ/ρ ) increase drastically below the pseudo-gap temperature, T*. This unexpected result attracts much attention in that it reflects the fundamental feature of the electronic state in the pseudo-gap region, which has been a central issue on high-Tc cuprates. In this article, we study these transport phenomena in terms of the fluctuation-exchange (Flex)+T-matrix approximation. We focus on the role of the vertex corrections (VC's) which are necessary to keep the conservation laws, and find that both ν and Δρ/ρ are strongly enhanced by the VC's due to the antiferromagnetic (AC) and the superconducting (SC) fluctuations. In conclusion, the pseudo-gap region in high-Tc cuprates is well described by the AF and SC fluctuation scenario based on the Fermi liquid theory. (author)