Incoherent Cooper pair tunneling and energy band dynamics in small Josephson junctions - A study of the Bloch Oscillating Transistor

TL;DR

This paper explores the properties of small Josephson junction devices, focusing on incoherent Cooper pair tunneling and energy band dynamics, and demonstrates the operation of a Bloch oscillating transistor as a mesoscopic amplifier.

Contribution

It applies phase fluctuation theory and energy band analysis to small Josephson junctions, realizing and characterizing a Bloch oscillating transistor with high current gain.

Findings

Current gain up to 30 measured in stable mode

Device functions as an amplifier for impedances 100 kΩ to 10 MΩ

Theoretical and simulation results align with experimental data

Abstract

We discuss the properties of devices of small Josephson junctions in the light of the phase fluctuation theory and the energy band structure, which arises from the delocalization of the phase variable. The theory is applied in the realization of a mesoscopic amplifier, the Bloch oscillating transistor. The device characteristics and comparison with theory and simulations are discussed. The current gain of the device in a stable operating mode has been measured to be as high as 30. Measurements on input impedance and the power gain show that the BOT is an amplifier designed for middle-range impedances, ranging from 100 k$\Omega$ - 10 M$\Omega$.