Experimental Studies on Cooper Pair Transport in Josephson Junction Arrays

Abstract

We have investigated how the transport properties of small-Josephson-junction arrays vary depending on a quantum control parameter (the ratio of the Josephson coupling energy E J to the charging energyE C ), the magnitude of dissipation, and the dimensionality d of the system. We found that the arrays show Coulomb blockade behavior when R S is larger than about dR Q (R Q ≡h/4e 2 = 6.45 kΩ) and E J /E C is smaller than a threshold depending on the value of R S and the dimensionality. The result is discussed in terms of quantum phase transition induced by the charging effect and the dissipation.

Intermediate bosonic metallic state in the superconductor-insulator transition

“…The saturating temperature dependence of the oscillation amplitude is consistent with that of the resistance, indicating that phase coherence saturation should be crucial to the formation of the anomalous metallic state. For the insulating films, as the link resistance rises beyond R Q = h/4e 2 with decreasing temperature, the inter-island capacitance and self-capacitances of the islands can produce a Coulomb blockade to Cooper pair transport (38). Thus, G osc and the phase coherence length decrease as the Cooper pairs become localized.…”