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The material with the rather complex name CsV₃Sb₅, composed of caesium, vanadium, and antimony atoms, does not occur naturally; it is synthesised as a high-quality crystal. It belongs to the family of so-called kagome metals, whose name has a simple origin: their atoms form a lattice reminiscent of the traditional Japanese woven pattern known as kagome. This distinctive geometry forces electrons to behave in unusual ways. Scientists are particularly interested in the fact that CsV₃Sb₅ exhibits a state known as a charge-density wave, associated with the breaking of conventional symmetries and unusual electronic phenomena.

From a "Blurry Photo" to Perfect Detail

This is where the method known as magneto-ARPES played a crucial role. The conventional ARPES technique – angle-resolved photoemission spectroscopy – works by shining light onto a sample, which ejects electrons whose direction and velocity can then be measured by scientists. In this way, researchers obtain something akin to a map of the “highways” along which electrons travel through the material.

Until recently, however, magnetic fields could not be used in such measurements. A magnetic field acts on the trajectories of electrons with a force that deflects them, which completely blurs the resulting image – rather like bringing a strong magnet close to an old cathode-ray screen. One might also imagine it as the distortion produced when a wide-angle camera lens exaggerates facial features at close range, or when a photograph becomes blurred due to motion.

Researchers managed to overcome this distortion not only through careful experimental tuning, but above all by developing advanced mathematical algorithms. These make it possible to calculate this unavoidable distortion retrospectively and remove it from the measured data. The result is a perfectly sharp picture of the electronic structure even under conditions that were previously considered impossible to measure.

“For a long time, magnetic fields were regarded as more of an obstacle than a useful tool in ARPES experiments. Here, however, they have become an active instrument that allows us to observe how the electronic structure changes under an external influence,” says Ján Minár, Deputy Director for Research and Development and head of the Advanced Materials Research team at NTC UWB.

Why Does It Matter for the Future?

In this experiment, the magnetic field acts as a subtle tuning parameter. Scientists adjust it slightly and observe which electronic states respond. Thanks to the new data-correction method, researchers can now obtain measurements with a level of precision that was previously unattainable. This will significantly facilitate the work of the global scientific community: instead of having to guess which features in the data represent real phenomena and which are merely noise caused by the field, scientists now have clear evidence.

“We have been able to directly link specific electronic orbitals with the observed symmetry breaking. This provides much more detailed information than conventional macroscopic measurements,” adds Aki Pulkkinen from NTC UWB.

The significance of the study is also reflected in its publication two days ago in Nature Physics, a journal that selects only the most important discoveries with the potential to shape the direction of modern physics. The ability to measure and mathematically correct the influence of magnetic fields with such precision opens the way towards materials for a new generation of electronics.

“If we understand precisely how magnetic fields influence electrons, we will be able to design components for quantum computers that are more stable, faster, and more energy-efficient,” adds Jan Minár.

Link to the article: https://www.nature.com/articles/s41567-026-03205-7