No abstract

We present a very-compact bicomponent-permanent-magnet design capable of generating 1.25 T in a small volume, significantly above the 0.6 T available from a single uniformly magnetized permanent magnet. In addition to the enhanced maximum field, our design drastically limits the stray field present around a standard permanent magnet. These features make it suitable for retrofitting existing experiments with a substantial magnetic field, in particular, scanning probes and optical, Raman, and photoemission spectroscopy, in diverse environments, from ambient to ultrahigh vacuum and over a wide temperature range.

Magnetic fields can have profound effects on the motion of electrons in quantum materials. Two-dimensional (2D) electron systems subject to strong magnetic fields are expected to exhibit quantized Hall conductivity, chiral edge currents, and distinctive collective modes referred to as magnetoplasmons and magnetoexcitons. Generating these propagating collective modes in charge-neutral samples and imaging them at their native nanometer length scales have thus far been experimentally elusive tasks. In this study, we visualize propagating magenetoexction polaritons at their native length scales and report their magnetic-field-tunable dispersions in near-charge-neutral graphene. Imaging of these collective modes and their associated opto-electrical responses at the sample edges is enabled by innovations to our cryogenic near-field optical microscope that allows us to nano-image the optical responses of 2D materials in magnetic fields up to 7 Tesla. This novel nano-magneto-optics approach represents a new paradigm for exploring and manipulating magnetopolaritons in specimens with low carrier doping via harnessing high magnetic fields.