Physicists at ETH Zurich have developed a quantum simulator that allows arranging atoms in a way that they mimic the behaviour of electrons in magnetic materials.
Magnetic materials owe their properties to the intricate interplay between a myriad of tiny magnets. These elemental magnets come typically in the form of individual electrons, each of which is weakly magnetic. Observable magnetism arises when these magnetic building blocks are arranged in specific patterns, in which they are held by quantum-mechanical interactions. A typical fridge magnet, for example, is composed of several ferromagnetic sections; in each segment all elemental magnets are aligned in parallel, giving rise to the known magnetic behaviour.
In other magnetic materials the situation is much more subtle, and the elemental magnets are arranged into more complicated patterns. Examples include so-called quantum spin liquids, where the elemental magnets interact in a way that prevents them from ever reaching an ordered state such as that found in a ferromagnet. Physicists and material scientists are interested in such unusual magnets as they are landmark problems in many-body quantum physics, but also because these materials possess properties that may be the basis of robust and compact magnetic data-storage devices or of novel forms of information processors.
The physicists build their artificial materials by making atoms to act like electrons and loading them into a “crystal” created by interfering laser beams. Both the laser beams and the trapped atoms can be controlled with exquisite accuracy. “In this way we can simulate the quantum-mechanical behaviour of different magnetic materials,” explains Esslinger, and adds: “One of our next goals is to address unsolved questions in the context of spin liquids.”
Exploring the properties of a quantum system with another one that can be better controlled is known as ‘quantum simulation’. In the past few years, there has been intense research into developing a quantum simulator for magnetic materials — this specific application is considered to be one of the main goals in the field. Esslinger and his team have now for the first time managed to construct such a device that directly reproduces the behaviour of a large number of electrons in a magnetic material.
“The key to our success has been a method that allows us to reach the extremely low temperatures required to explore quantum magnetism,” explains Daniel Greif, a PhD student in the group of Esslinger and first author of the study. With their method, the physicists were able to create a magnetic system containing 5’000 atoms. Teaming up with the group of Matthias Troyer, a professor at the Institute for Theoretical Physics, they are currently investigating whether the behaviour of this state can be reproduced on a conventional computer.
The flexibility of the quantum-simulation approach opens up an avenue to studying a wide range of possible scenarios of how electrons interact with each other. The results of these simulations can then be compared with the behaviour of natural magnetic materials, in order to gain insight into the mechanisms that defines their properties. But there is also the prospect of discovering magnetic behaviours that has not been seen yet in natural materials. This, in turn, could spur novel applications, says Esslinger: “Future technologies are often driven by the development of new materials like high-temperature superconductors, graphene or new magnetic materials.”
This story is reprinted from material from ETH, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.