Strongly coupled edge states in a graphene quantum Hall interferometer

TL;DR

This paper demonstrates how strong repulsive interactions between edge channels in a graphene quantum Hall interferometer cause phase jumps and Aharonov-Bohm frequency doubling, revealing insights into electron pairing phenomena.

Contribution

It shows that interaction-driven frequency doubling in a graphene quantum Hall interferometer can be explained by charge screening and edge channel interactions, advancing understanding of correlated 1D electron systems.

Findings

Observation of periodic phase jumps correlating with AB frequency doubling.

Tuning electron density modulates interaction strength and interference patterns.

Charge screening between edge channels explains the frequency doubling phenomenon.

Abstract

Electronic interferometers using the chiral, one-dimensional (1D) edge channels of the quantum Hall effect (QHE) can demonstrate a wealth of fundamental phenomena. The recent observation of phase jumps in a Fabry-P\'erot (FP) interferometer revealed anyonic quasiparticle exchange statistics in the fractional QHE. When multiple integer edge channels are involved, FP interferometers have exhibited anomalous Aharonov-Bohm (AB) interference frequency doubling, suggesting putative pairing of electrons into 2e quasiparticles. Here, we use a highly tunable graphene-based QHE FP interferometer to observe the connection between interference phase jumps and AB frequency doubling, unveiling how strong repulsive interaction between edge channels leads to the apparent pairing phenomena. By tuning electron density in-situ from filling factor {\nu}<2 to {\nu}>7, we tune the interaction strength and observe periodic interference phase jumps leading to AB frequency doubling. Our observations demonstrate that the combination of repulsive interaction between the spin-split {\nu}=2 edge channels and charge quantization is sufficient to explain the frequency doubling, through a near-perfect charge screening between the localized and extended edge channels. Our results show that interferometers are sensitive probes of microscopic interactions and enable future experiments studying correlated electrons in 1D channels using our highly tunable platform.