Zero-bias anomaly in one-dimensional ultrathin metallic nanowires

The electronic properties of ultrathin bimetallic Au/Ag nanowires with 2-3 nm in diameter were explored by scanning tunneling microscopy (STM) and scanning tunneling spectroscopy (STS) at liquid-nitrogen temperature. A pronounced dip around zero-bias, followed by a series of discrete single electron tunneling peaks at both negative and positive bias, is observed in the tunneling spectra. Several possible mechanisms, such as exchange interaction and Luttinger-liquid behavior, for the presence of the dip around zero-bias in the Au/Ag nanowires are excluded. Our experimental results and analysis indicate that the disorder of the bimetallic nanowire as the origin of the dip around zero-bias.