The upper critical field of thin superconducting films with large resistance

The influence of the electron-electron interaction on the upper critical fieldH_c2 of thin superconducting films with large resistance and of layered superconductors is investigated theoretically. The orbital effect only is taken into account. It is shown that the electron-electron interaction in the diffusion and Cooper channels influencesH_c2 in different manners. The interaction in the diffusion channel (dynamically screened Coulomb interaction) leads to essential deviations from the standard BCS dirty limitH_c2(T) curve at low temperatures and as a result upward curvature inH_c2(T) is possible. The interaction in the Cooper channel is significant only at temperaturesT_c–TT_c and enlarges the slopedH_c2(T)/dt atT=T_c.