"Magnetism in Graphene"
Magnetism in solids is one of the most striking manifestations of collective electronic behavior and spontaneous symmetry breaking. In graphene and other van der Waals materials, where electrons move in an atomically thin, perfectly crystalline environment, interactions can drive a remarkable range of correlated and topological phenomena. Using nanoscale superconducting quantum interference devices (SQUID-on-tip), we directly image the local magnetic response and thermodynamic quantum oscillations in rhombohedral and moiré graphene systems with unprecedented sensitivity. In the first part of the talk, I will discuss spontaneous magnetism in rhombohedral multilayer graphene. Exchange interactions among spin and valley degrees of freedom give rise to isospin magnetic textures, spin- and valley-polarized metals, and orbital ferromagnetism. These measurements reveal how intervalley exchange and Berry-curvature–driven orbital magnetization lead to spontaneous time-reversal symmetry breaking and rich isospin order. The quantitative local
magnetometry further enables direct estimates of the spin–orbit coupling and exchange energies, providing key constraints on the microscopic origin of the magnetic anisotropy [1].
In the second part, I will focus on field-induced magnetism, manifested through de Haas–van Alphen thermodynamic quantum oscillations of the magnetization. Imaging these oscillations in multilayer and twisted graphene systems reveals spatially resolved pseudomagnetic fields [2], Coulomb- and lattice-relaxation–driven band reconstructions, and magnetic breakdown [3], as well as interaction-induced nematic semimetal phases [4]. Together, these phenomena demonstrate how the interplay between electronic interactions and lattice relaxation reshapes the moiré band landscape.
The resulting measurements establish quantum oscillation imaging as a quantitative thermodynamic spectroscopy that directly resolves band topology, renormalization, and reconstruction with nanoscale precision—providing a powerful route to mapping the many-body energy landscape of strongly correlated two-dimensional systems.
