Quantum breakthrough: Time-Reversal Symmetry broken at record-breaking temperatures

Using muon spin rotation at the Swiss Muon Source SmS, researchers discovered that a quantum phenomenon associated with magnetic response varies with depth in the Kagome superconductor RbV”Sb”. This depth-dependence allows tunability: a fact that aids potential applications in quantum technology. Credit: Paul Scherrer Institute PSI / Mahir Dzambegovic

doi.org/10.1038/s41467-024-52688-6
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Scientists at the Paul Scherrer Institute (PSI) have discovered a quantum phenomenon called time-reversal symmetry breaking that occurs on the surface of a Kagome superconductor, RbV”Sb”, at temperatures as high as 175 K, or -98 degrees Celsius.

It may sound cold, but in the quantum world, that`s pretty hot! Normally, inside this material, time-reversal symmetry breaking occurs at a much lower temperature, around 60 K, or -213 degrees Celsius.

Yes, you read that right: the Kagome material is “breaking the rules” at a higher temperature than normal.

But why is this important”

What is time-reversal symmetry breaking?

Time reversal symmetry (TRS) is the idea that the laws of physics work the same whether time is running forward or backward.

In some materials, such as this superconductor Kagome, this symmetry can be broken, meaning the material behaves differently if time were reversed.

In the Kagome material RbV”Sb”, under certain conditions, electrons act together (a phenomenon called charge order), creating magnetic fields that break this symmetry.

This is interesting because it leads to unusual magnetic and transport properties, which could be useful for quantum technologies.

What is a Kagome material?

“Kagome” is a term inspired by a traditional Japanese basket-weaving pattern made of triangles that share vertices.

Physicists have discovered that when atoms are arranged in this pattern, the collective behavior of electrons generates exotic and fascinating quantum phenomena.

In the case of the material RbV”Sb”, one of the quantum properties is superconductivity, which appears at a super-low temperature of 2 K.

However, other quantum phenomena, such as the breaking of time-reversal symmetry, occur at higher temperatures.

Why is this so important?

The big point is that they discovered a special quantum property at a less extreme temperature.

Furthermore, this breaking of time-reversal symmetry varies with depth in the material, that is, it changes with the distance from the surface to the interior.

This means that it is possible to control the quantum phase.

This ability to “tune” the electronic and magnetic properties of the material at more accessible temperatures opens the door to using these phenomena in real technologies.

Where does this fit into the big picture?

This discovery is part of the search for unconventional superconductivity under more practical conditions.

The research team, led by Zurab Guguchia, had previously shown that TRS breaking is linked to superconductivity in this material.

While the current study didn`t directly probe superconductivity, the scientists believe it can also be tuned with depth, something they plan to investigate.

If this sounds familiar, you have a good memory! In 2022, Guguchia`s team published a key finding in the journal Nature showing the charge order that breaks TRS in a similar Kagome superconductor.

Since then, they”ve been studying how this phenomenon can be tuned and its connection to unconventional superconductivity.


Published in 11/11/2024 03h38


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