QF Fellow and Associate seminar: Owen Sheekey

Imaging spin and orbital magnetism in rhombohedral trilayer graphene

Rhombohedral graphene multilayers provide a clean and highly reproducible platform to explore the emergence of superconductivity and magnetism in a strongly interacting electron system. The high density of states near the van Hove singularities lead to a variety of broken symmetry phases – including exotic forms of spin and valley ferromagnetism [2, 3]. Because of their combined spin and valley ‘isospin’ degrees of freedom, these Stoner magnets exhibit an approximate SU(4) symmetry with a neardegeneracy in the many body phase diagram. In reality, this SU(4) symmetry is only approximate, weak symmetry breaking arises at both from single particle effect -- intrinsic spin-orbit coupling -- and from inter-particle interactions. Using a combination of nanoSQUID-on-tip (nSOT) magnetometry and measurements of inverse compressibility, we study the magnetic phase diagram of rhombohedral trilayer graphene (RTG). We directly image the spin and orbital magnetism that emerges when RTG is doped with either hole or electron carriers under a strong perpendicular electric field. Further, we study the character of these magnetic phases as a function of electronic density and perpendicular electric field.