Abstract
We focus on studying two kinds of tunneling properties of cuprate superconductors, namely, the Andreev reflection tunneling and the Josephson tunneling. In particular, we emphasize how the pseudogap of underdoped cuprates influence these tunneling properties.
In the discussion of Andreev reflection, our calculation semi-quantitatively explains the two gap scenario at underdoping revealed in tunneling experiments. The tunneling spectral we obtain is in good agreement with the experimental data. Our calculations support those models in which the pseudogap at underdoping is due to the partial truncation of the Fermi surface through an insulating gap in the antinodal regions, but not due to preformed Cooper pairs.
In the discussion of Josephson tunneling, we aim to test the cooperon physics in underdoped cuprates. Our calculation gives a good description of the temperature-dependent enhanced Josephson tunneling in experiments. More detailed analysis shows that the contribution from the cooperon excitation is significant and is comparable with that from the nodal quasi-particles.