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Tunneling of Cooper pairs across voltage biased asymmetric single-Cooper-pair transistors

J. Leppäkangas·E. Thuneberg·R. Lindell·P. Hakonen
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Abstract

We analyze tunneling of Cooper pairs across voltage biased asymmetric single-Cooper-pair transistors. Also tunneling of Cooper pairs across two capacitively coupled Cooper-pair boxes is considered, when the capacitive coupling and Cooper pair tunneling are provided by a small Josephson junction between the islands. The theoretical analysis is done at subgap voltages, where the current-voltage characteristics depend strongly on the macroscopic eigenstates of the island(s) and their coupling to the dissipative environment. As the environment we use an impedance which satisfies Re[Z]<<R_Q and a few LC-oscillators in series with Z. The numerically calculated I-V curves are compared with experiments where the quantum states of mesoscopic SQUIDs are probed with inelastic Cooper pair tunneling. The main features of the observed I-V data are reproduced. Especially, we find traces of band structure in the higher excited states of the Cooper-pair boxes as well as traces of multiphoton processes between two Cooper-pair boxes in the regime of large Josephson coupling.

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J. Leppäkangas, E. Thuneberg, R. Lindell, P. Hakonen. 2006-04-04. Tunneling of Cooper pairs across voltage biased asymmetric single-Cooper-pair transistors. https://doi.org/10.1103/physrevb.74.054504

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