Electronic correlation effects on optical, electronic and magnetic properties of materials through model Hamiltonians and Green’s functions

A. Honet1, L. Henrard1 and V. Meunier2

1Department of Physics and Namur Institute of Structured Materials, University of Namur, Rue de Bruxelles 61, 5000 Namur, Belgium

2Engineering Science and Mechanics Department, Pennsylvania State University

 

Optical or magnetic properties from materials can be deduced from their electronic properties. Among numerical techniques for electronic structure calculations, the most popular are ab initio techniques such as Density-Functional Theory. Besides model Hamiltonians that are parametrized and thus (semi-)empirical keep a huge interest. Indeed, the computational cost is reduced by several order of magnitudes, rending possible to model larger nanosystems or to account for effects that are usually set aside in ab initio computations, such as correlation. 

We present here a Green’s functions formalism applied to model Hamiltonians that allows for computing electronical, optical and magnetic properties of nanoparticles, including correlation, through the GW approximation of the Hubbard model. Optical properties of small polycyclic aromatic hydrocarbons have been previously investigated and compared to experiments (see Ref. 1). We show fundamental effects of correlation for very small systems [2] as well as preliminary results on the magnetic states of graphene nanoribbons (GNRs) that are extensively studied these last years, both numerically and theoretically (mostly within mean-field theory, neglecting correlation effects). These GNRs are now foreseen as potential building blocks for new electronic and spintronic devices.

Fundamental effects of correlation on electronic, optical and magnetic properties are still misunderstood while they are playing an important role in collective phenomena such as plasmons. 

 

 

  1. A. Honet, L. Henrard, V. Meunier, “Semi-empirical many-body formalism of optical absorption in nanosystems and molecules”, Carbon Trends 4, 100073 (2021).
  2. A. Honet, L. Henrard, V. Meunier, "Exact and many-body perturbation solutions of the Hubbard model applied to linear chains”, AIP Advances 12, 035238 (2022).