Physical Meaning of the Current Vertex Corrections: DC and AC Transport Phenomena in High-Tc Superconductors

Famous non-Fermi liquid-like behaviors of the transport phenomena in high-Tc cuprates (Hall coefficient, magnetoresistance, thermoelectric power, Nernst coefficient, etc) are caused by the current vertex corrections in neary antiferromagnetic (AF) Fermi liquid, which was called the backflow by Landau. We present a simple explaination why the backflow is prominent in strongly correlated systems. In nearly AF Fermi liquid, R_H is enhanced by the backflow because it changes the effective curvature of the Fermi surfaces. Therefore, the relaxation time approximation is not appricalbe to a system near a magnetic quantum critical point (QCP).