Time-reversal symmetry-breaking charge order in a kagome superconductor

Quantum material appears to break key symmetry

30 June 2022

Exotic superconducting materials can host a rare state of matter, which could be a precursor to interesting phenomena such as unconventional superconductivity.

First made in the lab in 2018, ‘kagome’ metals are so named because their crystal structure resembles the matting of traditional Japanese weaved baskets with their repeating ‘Star of David’ motif.

There have been tantalizing hints that some kagome superconductors may break ‘time-reversal symmetry’, so that the physics governing the system behaves differently depending on whether time goes forwards or backwards. But compelling evidence for this had been lacking.

Now, a team led by researchers from Paul Scherrer Institute in Switzerland has found that electric currents perform loops around the building blocks of the materials’ crystal structure, which strongly implies that time-reversal symmetry had been violated.

This finding suggests that kagome metals may exhibit other intriguing quantum effects.

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References

1. Nature 602, 245–250 (2022). doi: 10.1038/s41586-021-04327-z