Imaging magnon transport in a quantum Hall ferromagnet: Part 2*

The spin-polarized ν=1 quantum Hall state of monolayer graphene constitutes a unique laboratory for studying mesoscopic magnetic phenomena. Among many interesting properties, the system supports magnons which can be generated and detected electrically. Here we study the ν=1 state of graphene using a scanning single-electron transistor (SET) operated simultaneously as a local gate and electrometer. Processes involving localized states near device contacts are shown to strongly influence transport response, suggesting a microscopic mechanism for magnon generation and absorption. Moreover, operating the SET as an electrometer enables us to perform local compressibility measurements which further clarify the effects of magnon generation on the system.