The Critical Fluctuation of the Order Parameter in Type-II Superconductors

We study here the effect of the critical fluctuation (i.e. the thermodynamical fluctuation) of the order parameter in dirty type-II superconductors in a magnetic field H sligtly above the upper critical field. We find that the fluctuation gives rise to a singular contribution to various transport coefficients, which diverge like (H-Hc2)-1/2. It is shown at the same time that in the usual dirty superconductor (say, with the electronic mean free path l∼100 Å), the above effects will probably be unaccessible experimentally, because of the smallness of the coefficient in front of the singular terms. However, in extremely dirty superconductors (say with l∼ Å), we may expect significant modifications of the transport properties due to the fluctuation.