We investigate how coherent Cooper-pair tunneling depends on the competition between Josephson coupling energy Ej and charging energy Eq. Measurements were performed on a circuit consisting of two dc-SQUIDs in series, with a gate capacitively coupled to the central island. As the Ej/Ec ratio decreased, coherent Cooper pairs tended to tunnel incoherently. Measured data show good agreement with theoretical calculations in strong and weak coupling limits. This experiment implies the manifestation of Heisenberg's uncertainty principle in a superconductor.
All Science Journal Classification (ASJC) codes
- Physics and Astronomy(all)