Quantum Monte Carlo studies of edge magnetism in chiral graphene nanoribbons

We investigate chiral graphene nanoribbons using projective quantum Monte Carlo simulations within the local Hubbard-model description and study the effects of electron-electron interactions on the electronic and magnetic properties at the ribbons' edges. Static and dynamical properties are analyzed for nanoribbons of varying width and edge chirality and compared to a self-consistent Hartee-Fock mean-field approximation. Our results show that for chiral ribbons of sufficient width, the spin correlations exhibit exceedingly long correlation lengths, even between zigzag segments that are well separated by periodic armchair regions. Characteristic enhancements in the magnetic correlations for distinct ribbon widths and chiralities are associated with energy gaps in the tight-binding limit of such ribbons. We identify specific signatures in the local density of states and low-energy modes in the local spectral function which directly relate to enhanced electronic correlations along graphene nanoribbons. These signatures in the local density of states might be accessed by scanning tunneling spectroscopy on graphene nanoribbons.