Recent observations of quasi-particle gap via ARPES and STM revealed
important clues to the nature of superconductivity in the underdoped
cuprates. Here, we study the quasi-particle gap theoretically in the
presence of a larger pseudo-gap, within the strong coupling limit.
Without any free parameter, the resulting quasi-particle gap is found
to agree very well with the experimental observations. Most
surprisingly, at very low doping, the symmetry is found to deviate
significantly from the simple d-wave shape of the order parameter. In
contrast to the Bogoliubov excitation, a new interpretation of the
nature of the quasi-particles at the edge of the gap will be presented.