Functional renormalization group for d-wave superconductivity

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.