Regularization of the Density of States Fluctuation Contribution in Magnetic Field

Abstract

The fit of the experimental data on c-axis magnetoresistance of HTS above the transition temperature with the theory based on the fluctuation renormalization of the one-electron density of states (DOS) is exellent in weak magnetic fields but meets the noticible difficulties in the region of strong fields. This is due to the formal divergency of the DOS contribution to conductivity and the dependence of the cut-off parameter on the magnetic field itself. We propose the scheme of the regularization of the problem. This permits us to obtain the expression for the magnetic field dependent part of DOS conductivity as a convergent serie independent on cut-off. We also calculate analitically the asymptotics for all regions of magnetic fields. The results demonstrate the robustness of the DOS contribution with respect to the magnetic field effect: in strong fields it decreases logarithmically only while Aslamazov-Larkin and anomalous Maki-Thompson contributions diminish as powers of H_{c2}/H.