Beating Fabry-P\'erot interference pattern in a magnonic scattering junction in the graphene quantum Hall ferromagnet

TL;DR

This paper investigates magnon interference in graphene's quantum Hall ferromagnet at specific filling factors, revealing how spin and pseudospin modes create observable beating patterns that inform on the ground state's properties.

Contribution

It introduces a theoretical analysis of magnon interference in a Fabry-Pérot junction in graphene, linking interference patterns to the ground state's spin or pseudospin polarization.

Findings

Interference patterns depend on the ground state's polarization.

Beating patterns reveal information about low-energy anisotropies.

Pseudospin and spin modes exhibit similar interference behavior.

Abstract

At filling factor $\nu=0,\pm1$, the ground state of graphene is a particular SU(4) ferromagnet which hosts a rich phase diagram along with several spin, pseudospin or "entanglement" magnon modes. Motivated by recent experiments, we study a $\nu=-1|0|-1$ Fabry-P\'erot magnonic junction. If the ground state at $\nu=0$ is spin polarized, there exist two spin modes which interfere and create a beating pattern, while pseudospin modes are reflected. The same scenario occurs for pseudospin magnon if the $\nu=0$ ground state is pseudospin polarized. The observation of such an interference pattern would provide information on the low-energy anisotropies and thus on the ground state.