Advent calendar - December 12th - Gijsbert ten Hoven

In the Zernike Institute Advent Calendar, we are presenting 24 short spotlights in December. In these specials, we highlight PhD students, postdocs, support staff and technicians of our research groups and team - providing a glimpse into their typical day at work. In Episode 12 meet Gijsbert ten Hoven, PhD researcher in the Theory of Condensed Matter group of Prof. Thomas la Cour Jansen.

I am Gijsbert, a third year PhD candidate in the Theory of Condensed Matter Group. (Has it been over two years already?!) When people ask about my research topic, I usually tell them that I study the quantum mechanics of photosynthesis. Within our subgroup 'Computational Spectroscopy' we study the spectroscopic and transport properties of a wide variety of systems, with a particular focus on photosynthetic ones.

In my Bachelor days I studied Astronomy and Physics with a focus on theoretical subjects. During my Master's I continued this path to study Theoretical Physics and ended up doing a project in the ToCM group. This was a good experience and is how I ended up doing a PhD here. I was fortunate to have a relatively easy PhD start, as the friends I met during my master project helped me get into the PhD life.

My days are a balanced mix of writing papers, developing code, doing mathematical derivations and joining various discussions/meetings. I like developing theory and implementing it on the computer cluster. It is fun to try and put as much physics as possible into the computing power we have available. This forces us to ask which aspects to a problem are important and which are less relevant. My promotors and I discuss science almost every week and while we are quite goal oriented, it is particularly nice how leisurely these discussions can feel.

Last year we studied the timescales of energy transfer in chlorosomes, which are the light harvesting antennae of green sulfur bacteria. Chlorosomes are huge, self assembled molecular aggregates that consist of many thousands of chromophores. Their size and efficiency help green sulfur bacteria thrive in extremely low light conditions. Specifically, we modeled the exciton population transfer between aggregate layers, which is an important step in the overall functioning of the light harvesting complex. What I find so appealing about energy transfer in photosynthetic systems is that it is a key process for life on Earth. We can model the energy transport in these systems with a combination of techniques, such as molecular dynamics simulations and exciton theory software.

A cool thing that occurs in chlorosomes is that excitations are delocalised, meaning that they are shared over many molecules, such that incident light excites delocalised excitons. This 'collectively carried energy' is then funneled to the molecular reaction center, where it can be converted. My most recent work is a theory on higher order corrections and the role of system memory in exciton transfer, which we plan to apply to a variety of systems.

I am grateful to have been part of the research that was done by the two master students whom I supervised. They investigated the role of aggregate orientation in the excitation energy transfer that occurs in chlorosomes and made interesting predictions. Collaborating with others and supervising students are the most rewarding aspects of doing this PhD, and I often marvel at what can be achieved through collaborative effort.

Happy Holidays everyone!

See all Advent Calendar items 2025 here!