Correlation between transport properties and atomic configuration of atomic contacts of zinc by low-temperature measurements

We report low-temperature measurements of the electrical transport properties of atomic contacts of the superconducting metal zinc, arranged with lithographically fabricated mechanically controllable breakjunctions (MCB) as well as with MCBs made from whiskers. The conductance histogram shows several peaks\char22{}not regularly observed for multivalent metals. The first peak\char22{}corresponding to the single-atom contact\char22{}is located slightly below one conductance quantum and is split into two subpeaks, indicating two preferred configurations of the single-atom contact. The existence of two configurations can also be traced by analyzing individual conductance vs distance curves of the MCB. The current-voltage characteristics in the superconducting state show nonlinearities due to multiple Andreev reflections (MAR), which we use for determining the transport channels. With the help of a tight-binding model for the transport channels we establish a correlation between the preferred conductance values and preferred atomic configurations.