Parity effect in a superconducting island in a tunable dissipative environment

We have experimentally studied Coulomb oscillation in a superconducting single-electron transistor, where electromagnetic-environment impedance was controlled using a one-dimensional array of superconducting quantum interference devices. By decreasing environment impedance, the Coulomb oscillation exhibited a crossover from 2e to 1e periodicity. In addition, the 1e component was enhanced when additional noise was introduced by connecting a potential meter to the central island of the transistor. We propose a theoretical analysis for this parity effect that includes the effect of fluctuations arising from the finite noise temperature of the electromagnetic environment.