Effects of spin fluctuations on the tunneling spectroscopy in high-Tcsuperconductors

We investigate the effects of spin fluctuations on the tunneling spectra of the normal-metal–superconductor junction. In the high junction resistance limit, the dip/hump structure observed in ARPES data for the high $T_c$ superconductors is reproduced in a random-phase approximation treatment of the $t-t^{\prime }-J$ model. It is shown that the dip/hump structure weakens as doping increases as reflected in the data. In the other limit, we predict that the zero bias Andreev peak can coexist with the dip/hump structure. Furthermore, the c-axis tunneling spectra is found to be very similar to recent scanning tunnel microscope data once these fluctuations are included.