  Recent excperiments (ARPES, Raman) suggest the presence of two distinct
energy gaps in high-Tc superconductors (HTSC), exhibiting different doping
dependences. Results of a variational cluster approach to the superconducting
state of the two-dimensional Hubbard model are presented which show that this
model qualitatively describes this gap dichotomy: One gap (antinodal) increases
with less doping, a behavior long considered as reflecting the general gap
behavior of the HTSC. On the other hand, the near-nodal gap does even slightly
decrease with underdoping. An explanation of this unexpected behavior is given
which emphasizes the crucial role of spin fluctuations in the pairing
mechanism.
