Nadav Auerbach: Hole-doped rhombohedral tetralayer graphene: magnetic band reconstruction due to valley-Zeeman effect and visualizing isospin magnetic textures

"Hole-doped rhombohedral tetralayer graphene: magnetic band reconstruction due to valley-Zeeman effect and visualizing isospin magnetic textures"

Abstract: I will present our group’s recent experimental investigation of dualgated tetralayer rhombohedral graphene in the hole-doped regime. By combining zero field and finite field transport measurements with scanning SQUID-on-Tip (SOT) techniques, we identify multiple spontaneous isospin symmetry broken phases, including a full metal (FM) symmetric phase, a half metal (HM) phase, and a quarter metal (QM) phase. In both the FM and HM phases, we observe a distinct π-phase shift in quantum oscillations, which serves as a direct signature of a strong valley-Zeeman effect. We detect sharp magnetic transitions marking the onset of the HM and QM phases. Through 2D SOT magnetic imaging under both out-of-plane and in-plane magnetic fields, we demonstrate that the magnetic moments in the HM phase align closely with the applied field, putting a higher bound on the spin anisotropy in this phase. Conversely, in the QM phase, we find that the spin moments align with the orbital moments (out-of-plane), even in the presence of substantial inplane fields, providing a lower bound on the Kene-Mele type spin orbit coupling in ABCA graphene.