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Interview former PhD candidate Erik van Loon

'From electrons to material properties'

Erik van Loon - former PhD candidateErik van Loon was a PhD candidate in the department Theory of Condensed Matter of Prof. dr. Mikhail Katsnelson. His research was trying to find out how certain material properties emerge from the atomic structure of a material, one of the core missions of the Institute for Molecules and Materials (IMM).

Why do some materials conduct electricity while others do not? Material properties can change suddenly, with minor changes in the atomic structure.

From electrons to material properties

Van Loon was specifically looking at the behaviour of electrons in the material. The small negatively charged particles can often move within the material and determine some important properties, like magnetic and electronic behaviour. ‘These are features you want to exploit in future applications, like electronics and storage devices’, Van Loon says.

The research is theoretical, so there was little lab work for Van Loon. His computer is his lab, which ‘produces’ models and calculations. ‘We look at how and the particles move through the material’, he says. ‘Also, we try to calculate whether this behaviour changes when a magnetic field is applied to the material. In this way we can determine how fundamental material properties emerge.’

Ultra flat materials

A material called niobium sulphide has the special interest of Van Loon. It consists of only a one atom thick layer, like it’s more famous brother material graphene. For these ultra flat materials it is notoriously difficult to predict the properties, due to the large amount of electrons moving through the material. ‘The electrons also interact with each other. Therefore, you have to look at the collective behaviour of the particles. That is why the models often become complex and the calculations take very long. The only way to overcome this is to make use of approximations in the models’, Van Loon explains. The calculations are mostly done with a supercomputer of the IMM, and can take hours, days or even a week.

Side view of the molecular structure of niobium sulphide. Gunnar Schönhoff, Universiteit Bremen

World leading research

Van Loon did his Bachelor and Master in Physics at Radboud University. He also went to the University of Hamburg for an internship. After his Master he wanted to stay in Nijmegen. ‘I liked the city and university and I could continue the topic I was working on in Hamburg. On top of that the research of this department is world leading. It was a logical step to do this PhD project in Nijmegen.’

Next to the theoretical research like that of Van Loon, a lot of practical work is done within the IMM. Material properties are determined and tested in extreme environments, like experiments with graphene in high magnetic fields. Van Loon likes the interaction with the ‘experimental’ researchers. ‘You get to know the questions they have and the limitations of their experiments’, he says. ‘On the other hand you get a feeling of which questions they can answer for theorists like me. This is an advantage of being part of a broad research institute like the IMM.’

From physical problems to solving societal challenges

Van Loon also learned a lot of the courses he followed, like those on teaching and writing skills. ‘I particularly liked learning how to use acting techniques to give better presentations. That was an eye-opener for me’, he says.

Many companies have already introduced themselves during Van Loon’s PhD project. ‘There is an interest in PhD graduates in my field. Companies are looking for data analysts, for doing calculations of complex systems. You can often use experience of solving physical problems in addressing complex societal or economical questions.’