The temperature dependence of d-wave superconducting order for two dimensional fermions with d-wave attraction is investigated by means of the functional renormalization group with partial bosonization. Below the critical temperature T_c we find superconductivity, a gap in the electron propagator and a temperature dependent anomalous dimension. At T_c the renormalized "superfluid density" jumps and the approach to T_c from above is characterized by essential scaling. These features are characteristic for a phase transition of the Kosterlitz-Thouless (KT) type.
Categories: cond-mat.str-el cond-mat.supr-con hep-th