Controlling the magnetic properties of a single molecule

In today’s world, electronic computational devices are present everywhere around us. While they have proven to be a great driving factor for societal progress, computers have also started to contribute significantly to the global energy consumption. “More radical ideas to change the nature of the bits, the 1’s and 0’s, used in computational devices have recently been gaining ground. Proposals like quantum computing and spintronics (computers built out of magnetic circuitry) replace the electric current used in today’s electronics by magnetic signals instead. The large benefit that magnetic signals have over electric currents is that they are not susceptible to resistance and therefore are much more energy efficient”, says Dr. Lukas Veldman, post-doctoral researcher at the Institute for Functional Matter and Quantum Technologies (FMQ) at the University of Stuttgart. “While the idea of quantum computing is still in the very early stage of development, recent proof of concept measurements have been promising”, says the surface physicist.

“To build magnetic circuitry, we need to understand how these signals travel through materials, from one molecule to the next. In Stuttgart, we do this by isolating a single magnetic molecule and study how it interacts with its environment. The goal is to be able to control the magnetic moment via these interactions and build circuits out of a few coupled molecules.”

Veldman is currently working on a series of elaborate quantum experiments with which he hopes to clarify fundamental questions about the magnetic properties of certain classes of molecules. “Currently, our main goal is to understand how the tiny magnetic moments in molecules interact with each other and with their environment. These interactions are governed by the laws of quantum mechanics and have proven to be quite delicate and complex. Once fully characterized, we aim to use them to gain complete control over the magnetic properties of the molecules and start building conceptual devices for quantum computing and spintronics.”

These types of experiments studying single molecules are made possible by a class of remarkable instruments: scanning probe microscopes. These machines can zoom in so far that the individual atoms that make up matter become visible. “Our microscopy techniques are sensitive to the quantum dynamics of atoms and molecules. We can reveal previously unseen details and gain critical insights for novel technologies that operate at the atomic level," says Prof. Dr. Sebastian Loth, managing director of the FMQ and fellow of the Center for Integrated Quantum Science and Technology (IQST), Stuttgart.

Veldman, originally from the Netherlands, already developed expertise with this highly specialized microscopy technique during his doctoral thesis at the TU Delft. There, he studied magnetic interactions between individual atoms. “During my doctoral studies I used innovative techniques that were introduced to the field by two people: Prof. Sebastian Loth and Dr. Susanne Baumann. They both work in Stuttgart, so I knew where I had to go next.”

Veldman has been awarded a prestigious two-year Humboldt Research Fellowship for postdoctoral researchers to support his Stuttgart project. Through this fellowship program, the Alexander von Humboldt Foundation supports outstanding international scientists, allowing them to conduct research in Germany. Veldman deliberately chose the University of Stuttgart as his host institution. “Stuttgart offers an ideal environment for quantum researchers. I work here in a state-of-the-art laboratory and am part of a strong quantum community.”

In Stuttgart, Veldman is part of the Loth Group, which consists of 15 scientists from six countries. “In our research group, we test physical limits of miniaturization and study the emergence of quantum behavior in magnetic nanostructures and correlated-electron materials”, says Prof. Loth. “Lukas is a rising star in scanning probe science and we’re happy that he chose Stuttgart for his Humboldt fellowship.”