  We investigate the phase diagram of two-component fermions in the BCS-BEC
crossover. Using functional renormalization group equations we calculate the
effect of quantum fluctuations on the fermionic self-energy parametrized by a
wavefunction renormalization, an effective Fermi radius and the gap. This
allows us to follow the modifications of the Fermi surface and the dispersion
relation for fermionic excitations throughout the whole crossover region. We
also determine the critical temperature of the second order phase transition to
superfluidity. Our results are in agreement with BCS theory including Gorkov's
correction for small negative scattering length a and with an interacting Bose
gas for small positive a. At the unitarity point the result for the gap at zero
temperature agrees well with Quantum-Monte-Carlo simulations while the critical
temperature differs.
