Pieter Zeeman Prize for physics alumnus Berend Zwartsenberg
The biennial Pieter Zeeman Prize for the best Master thesis in physics has been awarded to Berend Zwartsenberg for his thesis entitled 'Taking control of the surface electronic structure of 3D topological insulators'.
The Pieter Zeeman Prize is organised and financed by the Foundation Pieter Zeeman Fund and brings its winner €2500. Responsibility for the selection process lies in the hands of the University of Amsterdam and the award ceremony is organised by the university in collaboration with the secondary school - Pontes Pieter Zeeman - in Zierikzee, the town where Zeeman was born and brought up, and with the council of Schouwen-Duiveland in Zeeland.
Berend Zwartsenberg was awarded the prize for his Master Thesis research into topological insulators, which he carried out under the supervision of Prof. Mark Golden. The prize jury - which chose to honour Zwartsenberg's work ahead of almost one hundred M-Phys theses - contained experts from particle physics (Ivo van Vulpen), experimental soft matter physics (Noushine Shahidzadeh) and theoretical physics (Bernard Nienhuis).
Electrons in crystalline solids live in what are called bands. These can be considered a kind of road network, and just like with roads a distinction is made between bands which are occupied (for bands: with electrons) and those which are empty. Insulators are materials in which one group of bands is filled with electrons and at higher energy another band or group of bands are empty. If temperature is insufficient for an electron to jump from the occupied set of bands (what we call the valence bands) up to the unoccupied set (the conduction bands), then the material does not conduct electricity and is thus an insulator.
In his thesis research, Berend Zwartsenberg conducted experiments based on the photoelectric effect, with which he was able to image the special surface states in topological insulator samples grown in Amsterdam. Using such images, he showed that it is possible to change the energy of these surface states using an ultraviolet light beam. To showcase this principle, Zwartsenberg showed that pre-defined patterns (in this case the acronym for the physics institute IoP) could be written into the surface state energy landscape of a topological insulator, in letters small enough to fit onto a human hair. These results provide a flexible and powerful 'knob' with which scientists and engineers can reversibly tune the electronic properties of these promising new materials.