Fully superconducting Bloch-oscillating transistor: Amplification and bifurcation based on Bloch oscillations and counterflowing Cooper pairs

TL;DR

This paper presents a fully superconducting Bloch-oscillating transistor that uses Bloch oscillations and counterflowing Cooper pairs for amplification and bifurcation, offering new control schemes in superconducting quantum devices.

Contribution

It introduces an alternative superconducting implementation of the BOT utilizing only tunnel junctions and reveals novel amplification mechanisms based on quasimomentum control.

Findings

Discovery of new amplification schemes using quasimomentum control.

Observation of resonant Cooper-pair transport in opposite directions.

Experimental and theoretical validation of the device's operation.

Abstract

The Bloch-oscillating transistor (BOT) is an amplifier that utilizes semiclassical dynamics of states in energy bands under traveling quasimomentum. In a BOT, a single quasiparticle tunneling across a base tunnel junction switches the state of a superconducting tunnel junction to a lower Bloch band, triggering a series of resonant Cooper-pair tunnelings through an emitter Josephson junction (Bloch oscillations). Here, we investigate experimentally and theoretically an alternative realization of this device, based only on superconducting tunnel junctions. We discover new amplification schemes, where the periodic motion of the quasimomentum is used to control charge transport between the electrodes. Remarkable, in operation the resonant Cooper-pair transport across the base Josephson junction occurs repeatedly to two opposite directions.