In the Van der Molen lab, we investigate the properties of low-dimensional materials, with an enthusiastic scientific team. We focus on two types of quantum systems.
First, we investigate charge transport (conductance) through molecules. The latter can be seen as quasi-one dimensional quantum systems, with properties that can be tuned by chemical synthesis. We have a specific interest in functional molecules, e.g. photochromic switches and spin-crossover compounds. J. Phys.: Cond. Matter 22 (2010) 133001
Second, we study the electronic properties of and charge transport in quasi two-dimensional systems. The most famous of these is undoubtedly graphene, a carbon layer of exactly one atom thick. But there are many more, e.g. hexagonal BN, MoS2 etc. Remarkably, such layers can be stacked to create novel materials with properites that we may be able to tune! To reach that point one day, we are accurately studying the electronic interaction between different layers within such 'Van der Waals materials'. We have a unique way to do this, thanks to special low-energy electron microscope (LEEM), that we have adapted to our needs.
Our Leem is called ESCHER. Due to its aberration correction, it has a record lateral resolution (1.4 nm). Still, our research program aims far beyond pure microscopy. One of our goals has been to make LEEM a key measurement system in condensed matter physics research as a whole and to use it for our research on Van der Waals materials, thin oxides and molecular layers in particular. Therefore, we have recently introduced various new techniques, such as LEEM-based potentiometry (Johannes Jobst), Angle-resolved reflected-electron spectroscopy (ARRES) (Nature Communications 6 (2015) 8926) and a novel form of transmission electron microscopy, operating at very low energies (eV-TEM) (Daniël Geelen). As a result, 'LEEM' is becoming an umbrella term for a measurement system that incorporates a plethora of unique techniques that can be used in real-time (also including LEED, dark-field imaging, ARPES, etc.).
ESCHER is part of the Leiden Center for Ultramicroscopy
VIDEO SHOT OF THE VAN DER MOLEN LAB.
Feel free to have a look at the video below. It features Daniël Geelen and Sense Jan van der Molen and was made by four Leiden MSc students (Sander van Lidth de Jeude, Jamie Culkin, Isabelle Jansen, and Anne Meeussen), together with Néstor Romero Clemente.
Our research group visiting former member Dr. Constant Guédon, at the Shell Laboratories in Amsterdam.