14.8.2026
Prof. Dr. Katharina Ollefs has been Professor of Solid-State Physics at Heidelberg University’s Kirchhoff Institute for Physics (KIP) since August 1, 2025– a fitting occasion for Managing Director of the Department Johanna Schwarz to look back with Katharina Ollefs on her first year at KIP. They talk about research on magnetic materials, the importance of bringing theory and experiment together, and why science and family life do not have to be at odds.
Johanna:
Katharina, you’ve now been at the Kirchhoff Institute for almost exactly a year. How did you experience your start in Heidelberg?
Katharina:
I felt very warmly welcomed right from the beginning – not only at the Kirchhoff Institute, but throughout the entire department. My colleagues were incredibly open and helpful. By now, we have also settled in very well as a family here in Heidelberg. Several colleagues supported me even before I officially started – whether with practical advice, for example about childcare, or simply by always being approachable. That made settling in much easier.
Johanna:
You came to Heidelberg from the University of Duisburg-Essen. What has that move meant for you, both professionally and personally?
Katharina:
The two faculties are quite different. The physics department in Duisburg-Essen is considerably smaller, with fewer students, and has a strong focus on solid-state physics. Heidelberg, by contrast, offers a much broader scientific spectrum. Here, I meet colleagues with very different perspectives and research interests. I find that kind of scientific exchange particularly exciting.
On a personal level, the move was a big step as well. I hardly knew Heidelberg before coming here. My husband studied here and had always really liked the city, so he particularly happy to come back.
Johanna:
What are you researching here at the Kirchhoff Institute, and how does your work connect with the research already being done within the department?
Katharina:
My research is essentially based on X-ray absorption. During my as a Postdoc at the European Synchrotron Radiation Facility in Grenoble, I already realized just how many different connections this method allows you to make. It can be used to study a wide variety of materials – from molecules and layered systems all the way to bulk materials – and to address very different scientific questions at the same time.
The most direct connection here at the institute is, of course, through solid-state physics, for example with Rüdiger Klingeler’s groupor in the Physical Chemitry department with Felix Deschler for example. But I also find the collaboration with Maurits Haverkort particularly exciting, because his theoretical work allows to describe exactly what I measure experimentally.
Johanna:
Why is the connection between theory and experiment so important?
Katharina:
I have actually always enjoyed working with theorists. When you look at an X-ray spectrum, you can already extract quite a lot of information just by looking at it. But to really understand in detail why certain signals appear and what they tell us about the material, you need theoretical models.
We do some of the simpler calculations ourselves within the group. But having the opportunity to work with specialists such as Maurits Haverkort means that we can really discuss the finer details. In the end, this close exchange leads to a much deeper understanding.
Johanna:
Sounds complex – can you explain it once more for all the non-physicists, in a “tell me like I’m five” format?
Katharina:
Absolutely: There is a story by Janosch in which Doctor Brausefrosch uses his X-ray machine to discover that the little tiger is ill because one of the stripes on his fur has slipped out of place. You can imagine our research in a somewhat similar way. We use X-rays to make things visible that you cannot see otherwise – for example, the domainwalls between magnetic domains in a permanent magnet, which can also shift.
To put it a little more scientifically: We use X-rays to look inside materials. This allows us to make structures visible that would otherwise remain hidden and to better understand why materials have certain magnetic properties.
Johanna:
From research to teaching: What can our students expect from your lectures?
Katharina:
Solid-state physics naturally plays a central role in my teaching. One particular focus is on magnetic materials and spectroscopic methods. In the upcoming semester for example, I will be offering a lecture on magnetic functional materials. The idea is to explore the physical principles that are crucial for the properties and functionality of these materials – for example, how to achieve a particularly large magnetic hysteresis in permanent magnets, or which physical processes are behind magnetocaloric materials.
What matters to me is not only teaching the fundamentals, but also showing why certain material properties are relevant for technological applications.
Johanna:
Staying with technological applications: What kind of benefit can your research have for society?
Katharina:
Among other things, we work on magnetic functional materials, for example for permanent magnets. If we can understand these materials better and thereby improve their properties, we can increase the efficiency of things like electric motors or wind turbines. That can make a direct contribution to the energy transition.
Magnetocaloric materials, which could potentially enable more efficient cooling systems in the future, are another focus of our research. The current heatwave makes it particularly clear just how much we need innovative cooling technologies.
Johanna:
Overall, what role does the potential for practical applications play in physics research for you?
Katharina:
For me, there are two sides to this. Fundamental research is incredibly important, and we shouldn’t make the mistake of judging research solely by the immediate gains in efficiency it might deliver. Many important developments come from simply trying to understand how something works. And sometimes that leads to entirely new, even disruptive possibilities that no one could have anticipated.
At the same time, I find it incredibly motivating when scientific findings eventually lead to real-world applications. If you see that your research has the potential to benefit society, I think it’s important to pursue that opportunity. That’s why I find spin-offs and start-ups so exciting: they take scientific discoveries a step further and show how fundamental research can ultimately translate into something that benefits all of us.
Johanna:
Is there anything from your career so far that has particularly shaped you?
Katharina:
There is one German saying I have never forgotten: “Mer muss och jünne künne (You have to be able to let others have their fun, too- a „law“from Cologne).” There isn’t really a perfect English translation, but to me it means recognizing that someone else’s success doesn’t take anything away from your own. There is an incredible amount of wisdom in that. It makes life much more relaxed when you don’t constantly compare yourself with others – and much happier when you can genuinely celebrate other people’s success. I think that is exactly what creates a good environment for collaboration, and it is something I definitely want to hold on to.
Johanna:
Is there an aspect of the faculty culture in Duisburg-Essen that you would like to transfer to Heidelberg?
Katharina:
Indeed, there is: In Duisburg-Essen, we started a Women’s Lunch. Women from across the department would meet for lunch at regular intervals, from scientist, technical and administrative staff to students. These were not big events, but simply opportunities to get together and talk. I always found that exchange incredibly valuable. Informal formats like this create space for questions, shared experiences and mutual support. I would therefore really like to establish something similar here in Heidelberg.
Johanna:
You moved to Heidelberg with your family. What helps you combine science and family life?
Katharina:
For me, the most important things are understanding and trust among colleagues. With young children, you simply cannot always plan everything perfectly. It helps enormously when colleagues know that you can be relied on even if you are not physically present in the office all the time.
I also really appreciate the University’s family-friendly initiatives. My children, for example, really enjoy activities such as the new Kinderkolloquium, the children’s lecture series. It makes them feel welcome here and they already feel a real sense of connection to the University. That has also made it much easier for us to settle in as a family.
And of course, a lot of this would not be possible without the support of my husband and our families. Whenever something unexpected comes up, my parents or my parents-in-law will, whenever they can, jump in the car and come over. I’m very grateful for that. It’s not something I take for granted.
Johanna:
And what do you do when you are not in the lab or the office?
Katharina:
I love spending time with my family, preferably outdoors. In the Odenwald or the Black Forest, for instance! Just last weekend, we went gemstone hunting together in the Spatschlucht. Although in the end, our pockets probably contained more stones than gemstones...
Johanna:
And what advice would you give to new colleagues coming to Heidelberg in the future?
Katharina:
Coming to Heidelberg, I have experienced first-hand how important it is for people to actively reach out to one another. That is exactly the kind of openness I would like to pass on. New colleagues should feel welcome from the very beginning – that is a culture we should definitely preserve.
Johanna:
Coming back to research one last time: What has excited you most in science recently?
Katharina:
That’s a good question.A lot, since I get excited about science easily.But actually, the first thing that comes to mind at the moment isn’t a new research result. What really impresses me at the moment is the spin-off „Magotherm“ led by Max Fries that emerged from the Functional Materials Group at TU Darmstadt. It is fascinating to see how they are managing to take this technology towards the market and demonstrate that these devices can be more efficient.
For me, it makes tangible that the work we do does not just stay somewhere in the lab, but can actually make its way into real life. And that is incredibly motivating – it makes me want to keep working on these materials and understand them even better.
Johanna:
Thank you very much for this wonderful conversation! I wish you every success as you build your “Complex Materials Spectroscopy” group, many exciting scientific moments ahead, and all the best to you and your family as you continue making Heidelberg your home!
KATHARINA OLLEFS
