Zero bias anomaly in the low-temperature scanning tunneling spectra of Sr3Ru2O7*

We have studied a zero bias anomaly in scanning tunneling spectra of Sr3Ru2O7 as function of temperature. The dip-like feature in the dI/dV spectra is observed in an energy range of --20meV to +20meV around Fermi energy. The depth of the dip decreases with increasing temperature in a temperature range of 5 to 30 Kelvin. The temperature dependence of the dip is not due to the thermal broadening connected to the tunneling process. The results on Sr3Ru2O7 are compared with temperature dependent scanning tunneling spectra of Sr2RuO4. Finally, we discuss different effects as possible explanations for the zero bias anomaly.