Physicists have discovered a fascinating phenomenon: when a material is made incredibly thin, it can transform and gain new properties.
A team led by Prof. Ursula Wurstbauer from the University of Münster has been exploring how to control the properties of these ultra-thin, two-dimensional crystals.
Their goal is to make these materials act like insulators, electrical conductors, superconductors, or even ferromagnets.
In their latest study, published in Physical Review Letters, the team achieved a breakthrough by demonstrating how the behavior of electrons within these crystals can be influenced by their energy landscapes.
This understanding could pave the way for new advancements in quantum technology.
To achieve these unique properties, the scientists stacked two layers of a two-dimensional crystal and twisted them slightly.
This twisting created moiré patterns, similar to the intricate designs seen when two layers of thin fabric overlap.
These patterns significantly slow down the movement of electrons, causing them to interact more intensely with each other, leading to what is known as “strongly correlated behavior.”
Prof. Wurstbauer explains that electrons within these moiré patterns “feel and see” each other. Because of the repulsion between electrons (as described by Coulomb’s law), a moiré lattice site near an electron can only be occupied with great difficulty or high energy input.
The resulting behavior of electrons depends on the specific pattern and the number of electrons present.
Wurstbauer uses the analogy of dancing to illustrate this concept. In a moiré pattern, electrons move unpredictably, like “wild” dancers at a disco, compared to the orderly dance patterns of traditional dances.
The way electrons “dance” or move within these patterns depends on the energy landscape created by the pattern and the number of charge carriers.
This research is not just important for basic science. The properties of these moiré crystal systems have potential applications in quantum technology and the development of neuromorphic components and circuits, which mimic the neural structures of the human brain.
The team, which included scientists from the University of Hamburg, RWTH Aachen University, and the Max Planck Institute for the Structure and Dynamics of Matter in Hamburg, combined experimental work with theoretical analysis.
They prepared different two-dimensional crystals, such as graphene, molybdenum diselenide, and tungsten diselenide. These samples were then analyzed using optical spectroscopy methods at very low temperatures, a technique known as resonant inelastic light scattering spectroscopy.
This innovative research opens up new possibilities for controlling the electronic properties of materials at the atomic level.
By manipulating the interactions between electrons and their energy landscapes, scientists can develop new technologies that could revolutionize various fields, from electronics to quantum computing.
Source: University of Münster.
