Thermoelectric Detection of Crossed Andreev Reflections in Quantum Hall/Superconductor Hybrid Structures

Hybrid structures that couple the chiral edge states of a quantum Hall insulator to an s-wave superconductor have emerged as a promising platform for non-Abelian quasiparticles and Cooper pair splitters. These devices can feature crossed Andreev reflections (CAR) that convert electrons from chiral edge modes that are upstream from the superconductor into holes that are injected into the downstream modes. Here, we interface the quantum Hall edge modes of cadmium arsenide (Cd₃As₂) films with a thin superconducting NbN strip. We observe oscillations in magnetic fields in the downstream resistance and thermoelectric response. While electron-like carriers dominate the sign of the ohmic response, likely due to the large elastic co-tunneling contribution, the downstream thermoelectric response alternates in sign. The results point to thermoelectric measurements as a promising probe to elucidate the competing nature of Andreev and tunneling processes at quantum Hall/superconductor interfaces.