Quantum Monte Carlo studies of edge magnetism in chiral graphene nanoribbons

TL;DR

This study uses quantum Monte Carlo simulations to explore how electron-electron interactions influence the magnetic and electronic properties of chiral graphene nanoribbons, revealing long-range spin correlations and spectroscopic signatures.

Contribution

It provides a detailed analysis of magnetic correlations and electronic states in chiral graphene nanoribbons beyond mean-field approximations, highlighting the effects of width and chirality.

Findings

Long-range spin correlations in sufficiently wide ribbons.

Enhanced magnetic correlations linked to energy gaps.

Spectroscopic signatures of electronic correlations accessible via STM.

Abstract

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 ribbon 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 and which can be accessed scanning tunneling spectroscopy.