Quantum charge pumping through a superconducting double barrier structure in graphene

TL;DR

This paper investigates quantum charge pumping in graphene with a superconducting double barrier, revealing that superconducting gaps enable large pumped charge via resonance, contrasting with minimal pumping in normal barriers.

Contribution

It introduces a novel superconducting double barrier setup in graphene for charge pumping, highlighting the role of superconducting gaps and resonances in enhancing pumped charge.

Findings

Superconducting gaps create a transmission resonance in the Delta_1-Delta_2 plane.

Enclosing the resonance contour results in large pumped charge.

Pumped charge behavior depends on pumping strength, phase difference, and incident angle.

Abstract

We consider the phenomenon of quantum charge pumping of electrons across a superconducting double barrier structure in graphene in the adiabatic limit. In this geometry, quantum charge pumping can be achieved by modulating the amplitudes (Delta_1 and Delta_2) of the gaps associated with the two superconducting strips. We show that the superconducting gaps give rise to a transmission resonance in the Delta_1-Delta_2 plane, resulting in a large value of pumped charge, when the pumping contour encloses the resonance. This is in sharp contrast to the case of charge pumping in a normal double barrier structure in graphene, where the pumped charge is very small, due to the phenomenon of Klein tunneling. We analyse the behaviour of the pumped charge through the superconducting double barrier geometry as a function of the pumping strength and the phase difference between the two pumping parameters, for various angles of the incident electron.