A novel 2-dimensional quantum substance has been discovered. The material is composed of atom-thin layers of cerium, silicon, and iodine (CeSiI) and is the first example of a two-dimensional material with heavy fermions. It is reported in a new study published in Nature by Uppsala University and other materials science specialists.
A new quantum material is unique as it has a 2D-like crystal structure with clearly separated, atom-thin layers. The layers consist of cerium, silicon and iodine (CeSiI) and are the first example of a 2D material with heavy fermions. Image Credit: Uppsala University
The electrons in CeSiI behave as if they have up to 100 times more mass than electrons in ordinary materials. This is why they are called heavy fermions. What is extra special about CeSiI is that this effective mass is anisotropic, that it depends on the direction in which the electrons move in the atomic layers.
Chin-Shen Ong, Researcher, Department of Physics and Astronomy, Uppsala University
The study is a partnership between researchers in materials theory at Uppsala University and Columbia University in the United States. Uppsala University materials researchers were primarily concerned with theoretically investigating the quantum characteristics of electrons in the material.
One family of materials where electrons interact very strongly is known as heavy fermion compounds. They coordinate their motions in what are known as quantum fluctuations to achieve this. The electrons behave as though they have up to 100 or 1,000 times more mass than electrons in typical materials because of this interaction.
Many yet unexplained quantum phenomena, including magnetism and unconventional superconductivity—the ability of an electric current to flow through a material without losing energy—are believed to be significantly influenced by these quantum fluctuations.
Although there have been decades of research on materials containing heavy fermions, up until now, the emphasis has been on materials with closely spaced atoms in three dimensions. With considerable success, Uppsala University researchers first turned their attention to cerium-based materials in the 1970s.
However, the new material—synthesized in a lab at Columbia University—is distinct because it has a crystal structure resembling two dimensions with distinct, atom-thin layers. The layers, which are the first instance of a two-dimensional material with heavy fermions, are made of cerium, silicon, and iodine (CeSiI).
Ong concluded, “With this discovery, we now have a significantly improved material platform for investigating correlated electron structures. 2D materials are like a construction kit with LEGO pieces. Our partners are already working on adding layers from other 2D materials to create a new material with customized quantum properties.”
Journal Reference:
Posey, V. A., et. al. (2024) Two-dimensional heavy fermions in the van der Waals metal CeSiI. Nature. doi:10.1038/s41586-023-06868-x.