New quantum state of matter found in exotic superconducting material

A new state of matter discovered in a “topological superconductor” could transform quantum technologies such as quantum computing and spintronics.

Topological superconductors have electron pairs in spin-triplet states where the electrons’ quantum spins are oriented in the same direction. These types of superconductors are of interest because they could theoretically be used to produce ultra-stable quantum computers.

Researchers at Cornell University’s Macroscopic Quantum Matter Group discovered and visualised a crystalline superconducting state in a new superconducting material called Uranium Ditelluride (UTe2). It is the first example of a “spin-triplet electron-pair crystal” state of matter.

Their findings are published in Nature.

In 2021 physicists’ theorised that UTe2 might show a topological pair-density-wave (PDW) state. Such a state in superconductors is found when paired electrons form periodic crystalline patterns in space. No such quantum matter had been found before.

“Our team at Cornell discovered the first PDW ever observed in 2016 using the superconductive-tip Scanned Josephson Tunnelling Microscope that we invented for that purpose,” says Dr Qiangqiang Gu. “For the UTe2 project, we have directly visualized the spatial modulations of the superconducting pairing potential at the atomic scale and found them to modulate exactly as predicted in a PDW state.

“What we detected is a new quantum matter state – a topological pair density wave composed of spin-triplet Cooper pairs.”

Cooper-PDWs involve pairs of electrons frozen into a superconductive state, instead of forming a conventional “superconductive” fluid where they all move freely in the same state.

Previously, the only bulk material to show spin-triplet superconductivity was the superfluid 3He.

“The discovery of the first PDW in spin-triplet superconductors is exciting,” Gu says. “Uranium-based heavy fermion superconducting compounds are a new and exotic class of materials that provide a promising platform for realisation of topological superconductivity.”

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