Scientists have finally solved the mystery of Fermi arcs

High-temperature superconductivity remains a significant puzzle in modern physics, with materials exhibiting zero electrical resistance only at low temperatures. Discovering a material that is superconducting at room temperature could lead to groundbreaking technological advancements.

Scientists at TU Wien have made progress in understanding cuprates, a fascinating class of high-temperature superconductors. They found that under certain conditions, electrons in these materials can move only in specific directions, represented as “Fermi arcs.” This phenomenon can be visualized using laser light to eject electrons from the material.

A team at the Institute of Solid State Physics at TU Wien has developed theoretical and numerical models explaining this effect, attributing it to the magnetic interactions among electrons from different atoms.

While explanations for superconductivity have existed for decades, including the 1972 Nobel Prize-winning BCS theory for metals, this theory does not apply to high-temperature superconductors like cuprates, which are copper-containing compounds known for their unique properties. Scientists Alessandro Toschi and Karsten Held noted that cuprates exhibit several unexplained phenomena, including the formation of “Fermi arcs.”

By adding extra electrons to these high-temperature superconductors and measuring their movement, the team discovered that electrons could only move in specific directions, represented by Fermi arcs that abruptly end at certain points. This behavior is unusual and cannot be explained by conventional theoretical models, highlighting the need for new approaches to understanding superconductivity in these materials.

The team at TU Wien, consisting of Paul Worm, Matthias Reitner, Karsten Held, and Alessandro Toschi, successfully explained the unusual behavior of Fermi arcs in high-temperature superconductors. They achieved this by developing complex computer simulations alongside an analytical model that simplifies the phenomenon into a straightforward formula. This advancement enhances the understanding of how these materials behave and could lead to further insights into high-temperature superconductivity.

Matthias Reitner said, “The key to the effect is an antiferromagnetic interaction. In the cuprates that we have modelled, this is an antiferromagnetic interaction with a long range.”

“The magnetic moments of the electrons on different atoms therefore align themselves over long distances in such a way that the magnetic orientation of the electrons always alternates between one direction and the other – similar to a chessboard, where each field is coloured differently to its direct neighbours.”

Paul Worm said, “For the first time, we were able to present a theoretical model for the abrupt end of Fermi arcs and explain why the movement of electrons in such materials is only possible in certain directions. This advance not only helps us to better understand some of the unsolved mysteries of high-temperature superconductors, but it could also advance future research into materials with similar unconventional properties.”

Journal Reference:

1. P. Worm et al., Fermi and Luttinger Arcs: Two Concepts, Realized on One Surface, Phys. Rev. Lett. 133, 166501. DOI: 10.1103/PhysRevLett.133.166501

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