Abstract
The quantum Hall (QH) effect supports a set of chiral edge states at the boundary of a 2-dimensional electron gas (2DEG) system. A superconductor (SC) contacting these states induces correlation of the quasi-particles in the dissipationless 1D chiral QH edge states. If the superconducting electrode is narrower than the superconducting coherence length, the incoming electron are correlated to outgoing hole along the chiral edge state by the Andreev process. In order to realize this crossed Andreev conversion (CAC), it is necessary to fabricate highly transparent and nanometer-scale superconducting junctions to QH system. Here we report the observation of CAC in a graphene QH system contacted with a nanostructured NbN superconducting electrode. The chemical potential of the edge states across the superconducting electrode exhibits a sign reversal, providing direct evidence of CAC. This hybrid SC/QH system is a novel route to create isolated non-Abelian anyonic zero modes, in resonance with the chiral QH edge.
Highlights
The microscopic picture of charge flow across the SC/quantum Hall (QH) system can be described by extending the Andreev process[1,2,3] between a SC and a normal conductor
When W
Unlike the case of the AES, the spatial separation of electrons and holes in CAC facilitates their independent detection by measuring the chemical potential of upstream and downstream edge states with respect to the ground SC electrode, which we demonstrate in this paper
Summary
The microscopic picture of charge flow across the SC/QH system can be described by extending the Andreev process[1,2,3] between a SC and a normal conductor. There can be two different regimes in this Andreev process, depending on the width of the SC electrode (W) compared to the superconducting coherence length ( s). When W >> s, the electron and hole will propagate along the edge of the SC electrode forming an Andreev edge state (AES)[1,2,3] (Fig. 1b).
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