Experimental determination of the Berry phase in a superconducting charge pump

TL;DR

This paper reports the first experimental measurement of the Berry phase in a superconducting Cooper pair pump, demonstrating the accumulation of geometric phase during adiabatic charge transfer and validating theoretical models.

Contribution

It provides the first direct measurement of the Berry phase in a superconducting charge pump, distinguishing dynamic and geometric phases experimentally.

Findings

Measured Berry phase accumulation per cycle

Quantified dynamic and geometric phase responses

Confirmed theoretical predictions of phase dependencies

Abstract

We present the first measurements of the Berry phase in a superconducting Cooper pair pump. A fixed amount of Berry phase is accumulated to the quantum-mechanical ground state in each adiabatic pumping cycle, which is determined by measuring the charge passing through the device. The dynamic and geometric phases are identified and measured quantitatively from their different response when pumping in opposite directions. Our observations, in particular, the dependencies of the dynamic and geometric effects on the superconducting phase bias across the pump, agree with the basic theoretical model of coherent Cooper pair pumping.