Ab-initio methods for electronic spectroscopy: Applications to bulk and layered semiconductors

Ab-initio methods for electronic spectroscopy: Applications to bulk and layered semiconductors

Optoelectronic properties are at the basis of remarkable technological applications, ranging from energy conversion to transparent electronics. Among the most powerful investigation tools are spectroscopy techniques such as photoemission, absorption, luminescence or electron energy loss spectroscopy. Theoretical simulations of spectral
properties are therefore essential on one hand as complementary tools for the analysis, but also to guide technological advances. Though, reliable predictions can not be obtained within standard approaches based on Density Functional Theory.
In the first part of the talk, I will progressively and didactically introduce state-of-the-art methods based on Many Body Perturbation Theory for the calculation of accurate band structure, of quasiparticle spectra and dielectric properties related to optical and electron energy loss spectroscopies. Theoretical results on paradigmatic semiconductors will be discussed and compared with measurements. The capabilities and limitations of the methods will be illustrated discussing some predictions and spectral analysis.
In the second part, I will focus on bidimensional systems. In this context, the standard supercell approach, which assumes periodic boundary conditions, hinders the simulation of isolated films. I will show how this problem has been partially solved in ab-initio calculations and how simple models can be employed to deal with this issue.
Recent results on black phosphorus will serve as examples.