Kateryna Kusyak awarded prize for best Master's thesis

Kateryna Kusyak, a PhD student in James McIver’s research group at the MPSD at CFEL, has been honored with the Jean-Marie Lehn and Klaus von Klitzing Prize for the best Master’s thesis in Nanoscience in the winter semester 2021/22.

Kateryna Kusyak © MPSD

In her thesis, Kateryna demonstrated how to increase the bandwidth of on-chip terahertz spectroscopy by 40%. This spectroscopy technique is used to investigate what color of light is absorbed by small solid structures. This information, in turn, provides new insights into the behavior of the electrons in the sampled material.

“Measuring these devices is challenging, because traditional optics can only focus light down to a specific size which is limited by physical fundamentals called the diffraction limit,” explains Kateryna. “For the color of light we are interested in, the size of the light beam is a hundred times larger than the size of the sample. My project was to expand the range of colors we can shine onto these samples, called the bandwidth.”

To generate a particular light color, researchers in the McIver group use a photoconductive switch which needs to flick from ‘on’ to ‘off’ at a particular speed. This speed determines how big the range of colors of the light is. However, unlike conventional switches, a photoconductive switch turns itself off again, without being switched by an operator.

“In my project, I figured out that if we make these switches in a different way, we can get them to turn off more quickly,” says Kateryna. “This quicker turn off time resulted in a larger bandwidth which equals more colors of light. Moreover, we changed the design of the guides contacting the switches, such that it is coupled capacitively, thus more bandwidth is achieved. The result of my thesis was an improvement of the bandwidth by 40% as well as the inclusion of a built-in referencing possibility.”

This approach makes it possible to investigate the phases of small Van-der-Waals heterostructures. Kateryna feels honored to receive this reward – and of the official recognition for her Master’s thesis: “Receiving the award is the cherry on the top of an amazing learning opportunity in a great work atmosphere with some of the best scientists. During my Master’s degree I learned a lot in the group which makes me incredibly grateful.”

Kateryna gained her Bachelor degree in Nanoscience at the University of Hamburg 2019. She has now started her PhD in physics with the McIver group as part of the Center for Non-equilibrium Quantum Phenomena, a collaborative research initiative between MPSD, the Max Planck Institute for Polymer Research, Columbia University and the Flatiron Institute in New York. She investigates photo-induced currents in Van-der-Waals materials related to topological states.