September 5, 2024 -- Chunyu Guo, group leader in the Department for Microstructured Quantum Matter at the MPSD, has been awarded a Starting Grant by the European Research Council (ERC) for his Free-Kagome project. He will investigate the novel effects of electronic correlations in the recently discovered AV3Sb5 family of Kagome superconductors using a sophisticated framework that isolates the samples from external influences and makes it possible to control them with extremely high precision.

The atomic structure of Kagome materials resembles the pattern of the Japanese basket weaving method which they are named after. A non-trivial electronic order may occur upon this lattice – a current orbiting within the unit cell, known asthe orbital loop current. It is also responsible for setting the handedness of the chiral charge order and creating a magnetic moment. This results in a robust entanglement between the magnetic, electronic, and structural degrees of freedom and means that manipulating one order can affect or modify another, akin to the unique electromagnetic responses of multiferroics. It also renders the intrinsic characteristics inaccessible through conventional means, as even slight variations in experimental conditions can significantly affect the physical properties of these materials.

In his ERC project, Chunyu Guo will investigate the intrinsic orbital dynamics in Kagome materials using three different approaches: By atomically engineering the 2D Kagome nets, thermally quenching them to create 3D Kagome glass, and optically controlling the chiral domains via polarized light. Each step will provide unambiguous information about the intrinsic electronic orders in AV3Sb5..

Guo and his team bring unique skills to this research area due to their scientific background as well as their expertise in the use of Focused Ion Beam (FIB) technology. The FIB permits the nanometrically precise fabrication of AV3Sb5. microstructures. The samples are suspended via extremely soft springs carved out of thin silicon nitride membranes. This unique, force-free set-up permits a significant strain reduction of more than 99% compared to a conventional set-up. Without it, the material would show drastic changes due to residual strain, making it impossible to probe its intrinsic properties.

“In the past few years, we’ve dedicated ourselves to developing this technique,” says Chunyu Guo. “Now, thanks to the ERC Starting Grant, we can finally pursue the fascinating correlated orders in Kagome superconductors.”

The project team will be based in the Department for Microstructured Quantum Matter, led by Philip Moll, which was established at the MPSD in 2021. Its researchers investigate quantum materials whose electrons fundamentally behave differently than those in materials like, for example, copper or silicon. They apply apply controlled strain and strain gradients to microstructured quantum materials which are impossible to achieve on the macro scale.