Cooper pair cotunneling in single charge transistors with dissipative electromagnetic environment

TL;DR

This paper investigates how dissipative electromagnetic environments affect Cooper pair cotunneling in superconducting single charge transistors, revealing suppression of current with increased resistance and modulation by gate charge.

Contribution

It demonstrates the impact of on-chip resistors on Cooper pair cotunneling and provides experimental insights into the control of supercurrent in superconducting transistors.

Findings

Cooper pair cotunneling is observed and characterized.

Increasing resistance suppresses the supercurrent at low voltages.

Gate charge modulates Josephson coupling and cotunneling current.

Abstract

We observed current-voltage characteristics of superconducting single charge transistors with on-chip resistors of R about R_Q = h/4e^2 = 6.45 kOhm, which are explained in terms of Cooper-pair cotunneling. Both the effective strength of Josephson coupling and the cotunneling current are modulated by the gate-induced charge on the transistor island. For increasing values of the resistance R we found the Cooper pair current at small transport voltages to be dramatically suppressed.