CONDUCTANCE STEPS AND QUANTIZATION IN ATOMIC-SIZE CONTACTS

The conductance of metallic contacts of atomic size has been studied u sing a scanning tunneling microscope at low temperature. As the contac t area is changed by pressing the tip into the sample, a series of rep roducible features and jumps in the conductance at integer multiples o f 2e2/h is observed. The jumps are interpreted as atomic rearrangement s, while the underlying conductance structure strongly suggests quantu m-size effects.