Quantum Phase Slip as a Dual Process to Josephson Tunneling

Superconducting properties of metallic nanowires can be entirely different from those of bulk superconductors because of the dominating role played by thermal and quantum fluctuations of the order parameter. Fundamental attributes of superconductivity such as zero resistivity, persistent currents in closed loops, energy gap in excitation spectra can be drastically violated by fluctuations. Here we report the experimental study of I-V characteristics of thin superconducting titanium nanowires governed by quantum phase slips. The thinnest samples imbedded in high-ohmic environment demonstrated counterintuitive behavior for a superconductor: Coulomb blockade. The magnitude of the Coulomb gap correlates with the rate of quantum phase slips. The observation confirms the similarity of quantum charge dynamics in a Josephson junction and in a quasi-one-dimensional superconducting channel governed by quantum fluctuations of the order parameter.