Highlighted papers December 2024 - January 2025

Materials with a ‘twist’ show unexpected electronic behaviour

In the search for new materials that can enable more efficient electronics, scientists are exploring so-called 2-D materials. These are sheets of just one atom thick, that may have all kinds of interesting electronic properties. If two sheets are placed on top of each other at specific angles, this may lead to new properties such as superconductivity. University of Groningen materials scientist Antonija Grubišić-Čabo and her colleagues studied such a ‘twisted’ material and discovered that it defied theoretical predictions.

Together with colleagues from Poland, Germany, France, and Italy, Grubišić-Čabo and her team studied sheets of a 2-D material called tungsten disulfide. According to theoretical predictions, when two sheets, (called a  bilayer), are stacked at an angle of 4.4 degrees, the electrons within the material should show a collective behaviour. ‘And when they are so closely connected, their collective behaviour can create new, fascinating effects,’ says Giovanna Feraco, first author of the study.

Collective behaviour

However, she did not see this collective behaviour in experiments, which can be explained by the interactions between atoms in the bilayer. The twist normally enables these interactions. ‘But by studying the electronic structure in the bilayer, we discovered that this material tends to “relax” into large, untwisted regions,’ Feraco explains. In technical terms, the twisted bilayer partially reverts to a lower-energy, untwisted configuration.

This finding highlights the importance of understanding how the two sheets of the bilayer form different regions with varying properties. The study has also enhanced scientists’ ability to predict and manipulate the behaviour of 2-D structures, paving the way for future applications in different types of electronics.

Reference: Giovanna Feraco et al: Nano-ARPES investigation of structural relaxation in small angle twisted bilayer tungsten disulfide. Physical Review Materials, 26 December 2024

International collaboration uncovers structure of Huntington’s disease protein

Huntington’s disease (HD) is an inherited disorder in which the nerve cells in parts of the brain gradually break down and die. It is caused by a protein called huntingtin, which forms unnatural clumps as a result of a mutation.

However, until now it was unknown what these clumps exactly look like, unlike in other diseases caused by clumping of defective proteins, such as Alzheimer’s or Parkinson’s. An international team of scientists, including University of Groningen Professor of Solid State NMR Spectroscopy Patrick van der Wel, has used a combination of computer and experiment-based techniques to present the first detailed picture of these disease-related clumps. The study provides new insights into the ‘fuzzy coat’ that these clumps have on their surface.

Diagnostics and treatments       

Similar to the clumps in Alzheimer’s and Parkinson’s, the clumps in Huntington’s disease are elongated shapes called fibrils. However, the Huntington’s fibrils differ in important ways from those in other fibril-induced diseases.

‘Knowing the structure of the protein clump is a critical piece of the puzzle of how these proteins play their role in the disease,’ says Van der Wel. It also paves the way for developing diagnostics and perhaps even treatments. ‘It’s important to monitor the disease proteins in patients, for example during experimental treatments.’ The project was supported by Huntington’s disease foundations, which are largely funded by families of patients and the general public.

Reference: Mahdi Bagherpoor Helabad, Irina Matlahov, Raj Kumar, Jan O. Daldrop, Greeshma Jain, Markus Weingarth, Patrick C. A. van der Wel & Markus S. Miettinen: Integrative determination of atomic structure of mutant huntingtin exon 1 fibrils implicated in Huntington disease. Nature Communications, 30 December 2024

Every month, the FSE Science Newsroom publishes a number of short articles on recent scientific publications from the faculty. On this page, you can read about the papers highlighted in December/January.