Coulomb blockade oscillation in a single atomic junction

Abstract

The first observation of the Coulomb blockade effect in the smallest possible system with a single atom as the central island of a double-barrier tunnel junction is reported. Our system consists of a single tungsten atom as the central island and a tungsten STM tip and a silicon reconstructed surface as the two electrodes. The use of a single atom as the central island makes the change in the electrostatic potential due to a variation of number of electrons in the island of the order of 1 eV and thus the Coulomb blockade effect is made more controllable and stable even at room temperature. A specific shape of the tip apex forms a tunnel junction between an apex atom and the rest of the tip with the energy-level broadening of the apex atom smaller than the change in the charging energy due to the change in the number of electrons in the single tungsten atom. This theoretical prediction was confirmed by the experimental results of I-V measurements with an STM tip made from a W(111) single-crystal wire where the change in the charging energy is 1.1 eV.