Dielectric screening in two-dimensional insulators: Implications for excitonic and impurity states in graphane

By P. Cudazzo, I. Tokatly, Á. Rubio. 2011

508 citations recorded by the source corpus.

For atomic thin layer insulating materials we provide an exact analytic form of the two-dimensional (2D) screened potential. In contrast to three-dimensional systems where the macroscopic screening can be described by a static dielectric constant, in 2D systems the macroscopic screening is nonlocal ($q$ dependent) showing a logarithmic divergence for small distances and reaching the unscreened Coulomb potential for large distances. The crossover of these two regimes is dictated by 2D layer polarizability that can be easily computed by standard first-principles techniques. The present results have strong implications for describing gap-impurity levels and also exciton binding energies. The simple model derived here captures the main physical effects and reproduces well, for the case of graphane, the full many-body $\mathrm{GW}$ plus Bethe-Salpeter calculations. As an additional outcome we show that the impurity hole-doping in graphane leads to strongly localized states, which hampers applications in electronic devices. In spite of the inefficient and nonlocal two-dimensional macroscopic screening we demonstrate that a simple $\mathbf{k}\ifmmode\cdot\else\textperiodcentered\fi{}\mathbf{p}$ approach is capable to describe the electronic and transport properties of confined 2D systems.

Subfields: Atomic and Molecular Physics, and Optics, Materials Chemistry

View Paper: https://www.semanticscholar.org/paper/001077e75f7e8854bf7343645a8bc1a43d2095c6

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In Atomic and Molecular Physics, and Optics

In Materials Chemistry

Citations in the corpus

VASPKIT: A user-friendly interface facilitating high-throughput computing and analysis using VASP code (2019, background): “(37)-(41) are not well-defined for low-dimensional materials since the dielectric function is not straightforward and depends on the thickness of the vacuum layer when the low-dimensional systems are simulated using a periodic stack of layers with sufficiently large interlayer distance L to avoid ar”
Calculating excitons, plasmons, and quasiparticles in 2D materials and van der Waals heterostructures (2017, background): “The reason for the large exciton binding energies in 2D materials is a combination of geometric confinement [87] and reduced dielectric screening [23, 41, 45].”
The Computational 2D Materials Database: high-throughput modeling and discovery of atomically thin crystals (2018, background): “it cannot be represented by a qindependent dielectric constant, and that Coulomb interactions tend to be weakly screened at large distances (small q vectors) [119, 161, 162].”
Excitons in van der Waals heterostructures: The important role of dielectric screening (2015, methodology): “[15] P.”