Resonant tunneling through a macroscopic charge state in a superconducting SET transistor

TL;DR

This paper predicts and experimentally confirms a resonant tunneling peak in a superconducting SET transistor's conductance, analogous to quantum resonant tunneling, with universal peak height and linear co-tunneling behavior.

Contribution

It introduces the concept of macroscopic resonant tunneling in superconducting SET transistors and demonstrates the universal peak height and co-tunneling characteristics.

Findings

Observation of a universal conductance peak with height e^2/2πħ.

Clear evidence of linear co-tunneling current away from resonance.

Theoretical prediction aligns with experimental results.

Abstract

We predict theoretically and observe in experiment that the differential conductance of a superconducting SET transistor exhibits a peak which is a complete analogue in a macroscopic system of a standard resonant tunneling peak associated with tunneling through a single quantum state. In particular, in a symmetric transistor, the peak height is universal and equal to $e^2/2\pi \hbar$. Away from the resonance we clearly observe the co-tunneling current which in contrast to the normal-metal transistor varies linearly with the bias voltage.