Impurity-induced magnetic moments on the graphene-lattice Hubbard model: an inhomogeneous cluster DMFT study

TL;DR

This study uses an advanced inhomogeneous cluster DMFT method to analyze how nonmagnetic impurities induce magnetic moments in graphene, revealing interaction-driven antiferromagnetic correlations and bound states, aligning with prior theories.

Contribution

It introduces the inhomogeneous cluster DMFT approach to study impurity effects in graphene, capturing dynamical correlations and providing insights into impurity potential and interaction strength.

Findings

Impurity induces local antiferromagnetic correlations.

Bound states are visible in the local density of states.

Results agree qualitatively with previous mean-field and DFT studies.

Abstract

Defect-induced magnetic moments are at the center of the research effort on spintronic applications of graphene. Here we study the problem of a nonmagnetic impurity in graphene with a new theoretical method, inhomogeneous cluster dynamical mean field theory (I-CDMFT), which takes into account interaction-induced short-range correlations while allowing long-range inhomogeneities. The system is described by a Hubbard model on the honeycomb lattice. The impurity is modeled by a local potential. For a large enough potential, interactions induce local antiferromagnetic correlations around the impurity and a net total spin $\frac12$ appears, in agreement with Lieb's theorem. Bound states caused by the impurity are visible in the local density of states (LDOS) and have their energies shifted by interactions in a spin-dependent way, leading to the antiferromagnetic correlations. Our results take into account dynamical correlations; nevertheless they qualitatively agree with previous mean-field and density functional theory (DFT) studies. Moreover, they provide a relation between impurity potential and on-site repulsion $U$ that could in principle be used to determine experimentally the value of $U$.