  The asymmetric tunneling in cuprate superconductors is studied based on the
kinetic energy driven superconducting mechanism. By taking into account the
interplay between the superconducting gap and normal-state pseudogap, the
essential feature of the evolution of the asymmetric tunneling with doping and
temperature is qualitatively reproduced. In particular, the asymmetry of the
tunneling spectrum in the underdoped regime weakens with increasing doping, and
then the symmetric tunneling spectrum recovers in the heavily overdoped regime.
The theory also shows that the asymmetric tunneling is a natural consequence
due to the presence of the normal-state pseudogap.
