Mott correlations in ABC graphene trilayer aligned with hBN

TL;DR

This study uses dynamical mean-field theory to analyze local electronic correlations in ABC trilayer graphene aligned with hBN, revealing significant spectral weight transfer and competing magnetic states near the Mott transition.

Contribution

It provides a detailed theoretical analysis of correlation effects and magnetic competition in ABC/hBN, highlighting phenomena occurring at realistic interaction strengths without symmetry breaking.

Findings

Spectral weight transfer occurs at moderate interactions relevant to experiments.

Onsite interactions induce antiferromagnetic states that may break C3 symmetry.

Electronic properties show anomalous temperature and doping dependence near the Mott transition.

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 moir\'e superlattice. This system has shown insulating phases at integer fillings of the moir\'e lattice, precisely the fillings at which a sufficiently strong Coulomb interaction (U$_{\rm Mott}$) 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$_{\rm Mott}$ 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.