Individual molecules and ultrathin superconductors under the microscope

Tuesday 12 December 2023, 10:30 am
PhD student
W.M.J. van Weerdenburg
prof. dr. A.A. Khajetoorians
dr. M.N. Steinbrecher

The laws of quantum mechanics play an important role in materials at the level of individual atoms. Quantum effects can be revealed using a scanning tunneling microscope (STM). Indeed, the extremely high resolution of an STM can visualise individual atoms and measure both electronic and magnetic properties of materials. In this PhD thesis, the STM technique was further developed to also measure dynamic properties at very low temperatures, only 30 mK above absolute zero. This allows a single individual molecule to be examined on a surface to learn more about its exact structure, dynamics, and magnetism. This thesis also investigates how a superconducting material, namely aluminium, changes as the material becomes increasingly thin, down to thicknesses of just four atomic layers. It turns out that the superconductivity in these ultra-thin layers is three times stronger and very robust against parallel magnetic fields. New insights into atomic magnets and superconductors support the development of the next generation of quantum computers. 

Werner van Weerdenburg studied Physics and Astronomy at Radboud University in Nijmegen, and obtained his Master's degree in 2018. During his studies, he gained experience in experimental materials physics at the High Field Magnet Laboratory, led by Professor Nigel Hussey, and later at the Scanning Probe Microscopy group, led by Professor Alexander Khajetoorians. In 2019, he started his PhD research in this group, investigating the magnetic properties of individual atoms and molecules. He worked on developing electron spin resonance and pump-probe techniques to study spin dynamics at temperatures as low as 30 mK. He also studied two-dimensional superconductors combined with high magnetic fields and individual atoms/molecules on semiconductors and superconductors.