Attractive correlation and charge skipping in a metallic grain capacitively coupled to a superconducting island

Cecilia Holmqvist (1, 2) , Denis Feinberg (3) , Alex Zazunov (4, 5)

1 NEEL - Institut Néel
2 MC2 - Department of Microtechnology and Nanoscience
3 NEEL - ThQC - Théorie Quantique des Circuits
4 LPM2C - Laboratoire de physique et modélisation des milieux condensés
5 CPT - Centre de Physique Théorique - UMR 6207

Capacitively coupling a normal metallic grain to a superconducting island can lead to attractive correlation (negative-U center) in the grain. The considered setup geometry is similar to that of a Cooper pair box coupled to a single-electron transistor, but operates in the regime of strong capacitive coupling. In the Coulomb staircase for the grain, positive steps ($+2e$) skipping odd charge numbers are found to be followed by negative ones ($-e$) signaling the occurrence of a negative differential capacitance. The condition for charge skipping is analyzed as a function of the ratio between the Josephson ($E_J$) and charging energies. The non-monotonous charging curves are calculated in the limits of large and small $E_J$.

Mots clés: Nanostructures; Superconductivity; Coulomb blockade

Domaines: Systèmes mésoscopiques et effet Hall quantique [cond-mat.mes-hall]

Cecilia Holmqvist, Denis Feinberg, Alex Zazunov. Attractive correlation and charge skipping in a metallic grain capacitively coupled to a superconducting island. 2007. ⟨hal-00136840v1⟩