Phys. Rev. Lett. 72, 3234–3237 (1994)2e to e periodic pair currents in superconducting Coulomb-blockade electrometersReceived 27 January 1994; published in the issue dated 16 May 1994 We have measured the current as a function of gate charge Q in superconducting Coulomb blockade electrometers with charging energies Ec≪Δ, the superconducting gap. We find a large pair current which exhibits a clear transition from 2e to e periodicity at about 250 mK. To explain our data, we propose an equilibrium model in which the current is due entirely to Cooper pairs. The periodicity change results from rapid shifts in the instantaneous effective Q, caused by fluctuations in quasiparticle number. We find good agreement, and predict the loss of 2e periodic current for large Ec. © 1994 The American Physical Society URL:
http://link.aps.org/doi/10.1103/PhysRevLett.72.3234
DOI:
10.1103/PhysRevLett.72.3234
PACS:
73.40.Rw, 73.40.Gk, 74.50.+r
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