Paul M. Haney
National Institute of Standards and Technology Gaithersburg
Orbital Magnetism in Metals and Moiré Materials
Location: 1080 Physics Research Building
Faculty Host: Roland Kawakami
Abstract: A collection of charged particles undergoing orbital motion forms an orbital magnet. Although the orbital magnetic moment in solids is often assumed to be quenched due to the crystal field, I’ll argue that electronic orbital moments in solids are in fact ubiquitous. The orbital moment underpins much of contemporary spintronics, and provides a tangible manifestation of topology in electronic structure. I’ll discuss aspects of orbital magnetism in two materials systems, with an emphasis on its experimental signatures. The first system is twisted double bilayer graphene, where the moiré lattice introduces strong valley-dependent orbital magnetism. The magnetic field response, embodied in the Landau level spectra, provides detailed information on the orbital magnetic properties of this material. The second system is a metallic thin film, where optical measurements of current-induced surface orbital magnetism are utilized to quantify phenomena such as the orbital Hall effect. I discuss the different components of orbital magnetism that contribute to this optical response, and argue that additional phenomena, such as the surface Pockels effect, play a role in these measurements.
Bio: NIST Website Biography
