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Johan Mentink: ‘Doing science is like a pilgrimage to the borders of knowledge’

Interview with dr. Johan Mentink (Ultrafast Spectroscopy of Correlated Materials)

Johan Mentink is Assistant Professor in the Ultrafast Spectroscopy of Correlated Materials (USCM) and Spectroscopy of Solids and Interfaced (SSI) departments within the Institute for Molecules and MaterialsJohan Mentink (IMM) at Radboud University. In this research group, Mentink studies ultrafast dynamics of condensed matter systems, especially the theoretical description and numerical simulation of (quantum) many-body effects in the ultrafast dynamics of magnetism. He is well-known for the strong interactions with experimentalists and actively involved in the application of ultrafast magnetic phenomena for the development of new concepts for faster, smaller and more energy-efficient computing.

Mentink lives in Oosterbeek, together with his wife and children.

We interviewed Johan Mentink about his research background, his research focus within IMM and himself.

Where exactly did your curiosity for science start?

“I have always been interested in how things work. As a child, I built a lot of technical Lego. Even then, how it was put together fascinated me. I was curious about the mechanisms behind it; how and why do things work the way they do.”

What did you study?

“I studied technical engineering (in Dutch: LTS and MTS) and applied physics at the Fontys University of Applied Sciences in Eindhoven. After the first year, I continued my bachelor and master studies at the Eindhoven University of Technology (TU/e). After graduation, I combined physics and engineering and worked on infrasound at the Royal Netherlands Meteorological Institute (KNMI) for some years. In this job, I was actively involved as researcher in the LOFAR project. As physics remained close to my heart, I followed scientific updates closely. Via Tijdschrift voor Natuurkunde, I learned about the research of professor Rasing. Immediately I was interested in the fundamental research performed in his group that could trigger revolutions in future technology. Later, I started as PhD candidate in his group.”

What was your PhD research about?

“My research was a collaboration with the group of Professor Katsnelson where I focused on developing theory to understand the all-optical switching. At that time this effect was just discovered experimentally and we did not have a clue how it worked. It was an extremely inspiring atmosphere in Rasing’s group with lots of interactions between theory and experiments. It inspired me as the fundamental studies offered me a very broad perspective. Can we push the boundaries of knowledge in magnetism and make the impossible possible?”

What did you do after your PhD?

“I was awarded a Rubicon Grant to work as postdoctoral researcher at the University of Hamburg. The aim of the project was to find out how to manipulate the strongest interactions in magnetism, to ultimately exploit these forces to manipulate magnetism on faster time scales. It was a new and challenging research environment for me and I could further build my network with other theoretical and experimental physicists. Meanwhile, I also continued working together with the experimental and theoretical groups in Nijmegen, and mastered new computational methods.”

How did you end up at Radboud University?

“Towards the end of my postdoc project, I was asked by Professor Misha Katsnelson to work as post doc in his group. I returned to Nijmegen and there I received a VENI grant to further develop my research line. Subsequently, I received a grant from NWO and Shell, which allowed me to start as tenure track assistant professor in the SSI group.”

What is your research focus now?

“We want to understand magnetism on the shortest length scale and time scale. In this condition, magnets behave very differently than normal. One example is the very small topological spin patterns, the so-called skyrmions. With the new European XFEL and supported by numerical simulations, my collaborators and I have discovered a new much faster route to create skyrmions. This exemplifies again the close interaction with experimentalists. But I also work on predictions for new experiments. To this end we apply and develop new methods inspired by machine learning, with which we can simulate the effect of very strong quantum many-body effects for the first time. Eventually, this may lead to new concepts for much faster, smaller and more energy-efficient data storage and information processing.”

skyrmions

What makes you happy going to work every day?

“I enjoy working with students, from giving lectures to supervision and performing research together. In my research, I love to disclose new physics and obtain deeper understanding. To take up the challenge to understand how things work. And very important, be active in outreach to help others understand it too.”

You are a pioneer in science, aren’t you?

“Pioneers utilize and apply their expertise to drive forward innovation. To some extent, I feel like a pilgrim on the route to the borders of knowledge; searching for the ‘greater’ or ‘higher’ which brings broad perspectives! Science is also a service to society, aiming to discover fundamentally new things for a better world of tomorrow. Our knowledge needs to progress, the real power of science is not just to optimize something, but to make things possible that you could not have imagined before."

You are actively involved in Green IT. Tell us more about this.

“Data plays a crucial role in the 21st century economy and society. With the continuous increase of the amount of produced data, and the corresponding rapid increase of the energy consumption, finding ways to store data faster, at higher density and with less energy has become a major challenge. Currently the knowledge to meet all these demands simultaneously is missing, which limits technological development. Our goal is to understand and fully control magnetism on the shortest possible timescale operating on ultra-small dimensions with ultralow energy cost. On the long term, this may lead to novel concepts for more sustainable data storage and data processing (e.g. datacenters, hard disk drives, computers). On shorter term, we also try to be more energy-efficient ourselves. For example, we were recently awarded a GreenIT voucher, to collaborate with companies like IBM and benchmark todays neuromorphic chips for more energy-efficient numerical simulations."

You like working in IMM, do you?

“I sure do! I like working together in interdisciplinary projects, IMM is an excellent place for that. There are many opportunities to work together with other IMM groups, as exemplified for being involved in two departments (SSI and USCM), which both focus on very similar topics with experimental methods. Science really is teamwork, the pilgrimage never occurs in isolation. Looking at the same problem from different perspectives enriches me. Together we can make much more impact!”

Text: Miriam Heijmerink