Mott correlations in ABC graphene trilayer aligned with hBN

Abstract

The nature of the correlated phases found in some graphene heterostructures is under debate. We use dynamical mean-field theory (DMFT) to analyze the effect of local correlations close to half-filling on one of such systems, the ABC trilayer graphene aligned with hexagonal boron nitride (ABC/hBN), which presents a moiré superlattice. This system has shown insulating phases at integer fillings of the moiré lattice, precisely the fillings at which a sufficiently strong Coulomb interaction (U${}_{\mathrm{Mott}}$) may produce a metal-insulator Mott transition. Our calculations show that the electronic states are strongly affected by a significant spectral weight transfer at interactions with magnitudes expected to be relevant in experiments. This effect, which emerges at interactions considerably smaller than U${}_{\mathrm{Mott}}$ and does not require symmetry breaking, impacts the electronic properties at temperatures above the magnetic transitions producing anomalous temperature and doping dependences not present without alignment to hBN. Close to the Mott transition we find that onsite interactions promote an antiferromagnetic (AF) state, probably breaking the C${}_3$ symmetry, that will compete with the ferromagnetism arising from intersite exchange interactions to determine the ground state.

9 pages, 4 figures (including the supplemental material)

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• Topological flat bands in rhombohedral tetralayer and multilayer graphene on hexagonal boron nitride moire superlattices
• Strong correlations in ABC-stacked trilayer graphene: Moiré is important
• Spin-valley magnetism on the triangular moiré lattice with SU(4) breaking interactions
• Analogue of atomic collapse for adatoms on rhombohedral multilayer graphene