Unusual quantum phenomena: Competition between magnetic orders

The system: A crystal lattice made of light traps atoms in several bilayer sheets. Tomographic images show the (spin-) densities in a single layer. They provide information about the magnetic ordering of the atoms. The image on the right shows the density of one layer averaged over twelve realizations (orange red). Credit: © Marcell Gall, Nicola Wurz et al./ Nature

Researchers at the University of Bonn have used ultracold atoms to gain new insights into previously unknown quantum phenomena. They found out that the magnetic orders between two coupled thin films of atoms compete with each other.

The team uses so-called quantum simulators, consisting of ultra-cold atoms, which mimic the interaction of several quantum particles. Even state-of-the-art computer models cannot calculate complex processes such as magnetism and electricity down to the last detail.

The atoms are cooled down using lasers and magnetic fields. The atoms are located in optical lattices, i.e. standing waves formed by superimposing laser beams. This way, the atoms simulate the behavior of electrons in a solid state.

Within the quantum simulator, the scientists have, for the first time, succeeded in measuring the magnetic correlations of exactly two coupled layers of a crystal lattice.

To study the distribution of atoms in the optical lattice, the physicists used a high-resolution microscope with which they were able to measure magnetic correlations between the individual lattice layers. In this way, they investigated the magnetic order, i.e. the mutual alignment of the atomic magnetic moments in the simulated solid state. They observed that the magnetic order between layers competed with the original order within a single layer, concluding that the more strongly layers were coupled, the more strongly correlations formed between the layers. At the same time, correlations within individual layers were reduced. (SciTechDaily)

The work has been published in the journal Nature.

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