Imaging magnon transport in a quantum Hall ferromagnet: Part 1

Graphene exhibits quantum Hall ferromagnetism at partial fillings in the N=0 Landau level where its SU(4) isospin symmetry is spontaneously broken due to strong electron-electron interactions. It has been demonstrated that it is possible to generate and detect magnons, collective excitations of spins, in the ν= ±1 quantum Hall ferromagnets by exploiting equilibration of spin-polarized edge states. However, the nature of magnon transport in the system is still under active investigation. In this two-part talk, we will discuss scanning gate microscopy (SGM) of magnon transport in the graphene quantum Hall ferromagnet. Using a metallic scanning tip, a small region of graphene can be gated away from integer filling, effectively acting as a barrier for magnon transport inside the system. In this talk, we present a general scheme of performing SGM of magnon transport, and report observation of localized response in transport as we place the local barrier near the magnon generation and absorption sites.