Quantum charge fluctuations in a superconducting grain

M. Houzet, D. A. Pesin, A. V. Andreev, L. I. Glazman

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12 Citations (Scopus)


We consider charge quantization in a small superconducting grain that is contacted by a normal-metal electrode and is controlled by a capacitively coupled gate. At zero temperature and zero conductance G between the grain and the electrode, the charge Q as a function of the gate voltage Vg changes in steps. The step height is e if Δ<Ec, where Δ and Ec are, respectively, the superconducting gap and the charging energy of the grain. Quantum charge fluctuations at finite conductance remove the discontinuity in the dependence of Q on Vg and lead to a finite step width G2Δ. The resulting shape of the Coulomb blockade staircase is of a novel type. The grain charge is a continuous function of Vg while the differential capacitance, dQ dVg, has discontinuities at certain values of the gate voltage. We determine analytically the shape of the Coulomb blockade staircase also at nonzero temperatures.

Original languageEnglish
Article number104507
JournalPhysical Review B - Condensed Matter and Materials Physics
Issue number10
Publication statusPublished - 1 Sep 2005
Externally publishedYes


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