Humboldt-Universität zu Berlin - Faculty of Mathematics and Natural Sciences - Theory of excitations in low-dimensional systems


Are you interested in doing your Bachelor / Master Thesis in a young and stimulating environment?
Contact us! We are working on several topics about light-matter interaction from first principles.
You may have a look at our recent works here.
Examples of thesis topics are reported below. Please consider that these are general themes. Bachelor / Master theses will be flexibly designed together with the candidate, considering her/his interests and skills, as well as the given time frame. Whenever possible, collaborations with experimental partners and/or other theory groups are envisaged. 


Doping in organic semiconductors

We investigate doping in organic semiconductors by means of first-principles methods. We are interested in identifying the fundamental physical mechanisms leading to doping that occur when donor and acceptor molecules are brought together. To achive this goal it is essential to characterize the electronic stucture of the individual components. We propose Bachelor and Master thesis topics in this research area in close collaboration with our experimental partner groups. 

Reference: P. Beyer, et al., Chem. Mater. in press (2019).

First-principles characterization of materials for photocathodes from many-body perturbation theory

The on-going efforts towards the next generation of X-ray electron free lasers and other light sources goes hand in hand with the development of optimized photocathodes that enable this technology. In this respect, materials science and the most advanced computational techniques related to it can provide a significant contribution to the field. The goal of this study is to provide an in-depth characterization of semiconducting materials for photo-cathodes. For this purpose, beyond-DFT methods based on many-body perturbation theory will be employed to achieve a quantitative description of key properties such as band structures, band gaps, optical absorption spectra, and excitation character. This work is part of a collaboration with the group of Dr. Thorsten Kamps at the Helmholtz-Zentrum Berlin.


Ultra-fast dynamics and nonlinear optical properties of light-absorbing systems from first principles 

The response of light-harvesting systems to intense laser sources is a crucial topic in view of exploiting such systems in practical applications. The advent of ultra-fast laser techniques has enabled the study of the excitations in their earliest stage of formation. Concomitantly, the irradiation from intense beams triggers nonlinear response of the absorbing elements. The goal of this project is to describe, analyze, and understand the fundamental mechanisms ruling these phenomena. This study will be performed in the framework of real-time time-dependent density-functional theory. Depending on the candidate’s skills and interests, methodological advancements, computational developments, and/or a detailed description of realistic systems are envisaged.

Reference: C. Cocchi et al., Phys. Rev. Lett. 112, 198303 (2014).


Light-matter interaction in low-dimensional materials and heterostructures

The possibility of designing novel materials by vertically stacking two-dimensional layers has been attracting increasing attention in the last few years throughout an interdisciplinary community of physicists, chemists, and material scientists. In particular, the combination of dielectric and metallic layers can open fascinating perspectives to further tune the response of the systems to electromagnetic radiation. An interesting aspect to investigate is how building blocks with different and possibly complementary behavior with respect to light absorption behave when forming a heterostructures. The scope of this work is to determine the nature of the excited states in these materials and to understand whether and how different types of excitations interact or even enhance each other. Excited-state properties will be computed from first-principles, in the framework of density-functional theory and many-body perturbation theory. Methodological and code developments are envisaged to study systems of technological relevance.

Reference: W. Aggoune, C. Cocchi et al., J. Phys. Chem. Lett. 8, 1464-1471 (2017).