Enhancement of the Chiral Andreev Edge State Interference Signals

We study the interference effects of chiral Andreev edge states (CAES) formed along the

interface of a quantum Hall (QH) edge and a superconductor, as reported earlier by our

group. The modes consist of electron and hole states hybridized by the superconductor,

which propagate along the contact interface in the direction determined by the magnetic

field. Specifically, we observe CAES interference in the form of voltage fluctuations

downstream from the grounded superconducting contact. Our previous measurements of the

downstream voltage fluctuations have produced small signals which inhibit the prospect of

coherently manipulating the CAES. Further studies have produced larger signals, however

the fabrication parameters responsible are poorly understood. Here we discuss attempts to

increase the prominence of the interference effects through studies of the

superconductor-graphene interface. Devices of different materials and various interface

lengths are considered to better understand the parameters determining the signal strength.

We also present fabrication techniques that are expected to improve device performance.