Published Article Nature 618, 921 - June 2023

The properties of superconducting materials, their perfectly dissipationless electronics, perfect diamagnetism, and macroscopic quantum mechanical dynamics are all the products of the formation of a macroscopic quantum fluid of electron pairs. To better understand this, we have developed the first scanned Josephson/Andreev tunneling microscopes (SJTM/SATM) which provide direct access to the macroscopic quantum electron pair condensate.

Since the 1960s the possibility of a crystalline superconducting phase within the overall fluid has been discussed with great interest in the superconducting community. Such a state should manifest itself as a spatially periodic electron-pair crystal; we call this state a Pair Density Wave (PDW). For years the superconducting community had suggested that such a PDW state might exist in the high-temperature superconductor Bi₂Sr₂CaCu₂O_8+x. In 2016 our group developed our first SJTM system and subsequently detected this long predicted PDW state. Since then we have discovered PDWs in several other materials including in the transition metal dichalcogenide superconductor NbSe₂.

Recently our focus of study has been the spin-triplet topological superconductor UTe₂. This class of superconductor should exhibit many unprecedented electronic properties including fractionalized electronic states relevant to quantum information processing. In UTe₂ we searched for a PDW state, by visualizing the pairing energy-gap with µeV-scale energy-resolution made possible by a superconducting SATM tip. We discovered three PDWs at incommensurate wavevectors P_i=1,2,3 that are indistinguishable from the wavevectors Q_i=1,2,3 of the prevenient CDW. From these observations and given UTe₂ as a spin-triplet superconductor, this PDW state appears to be the first known spin-triplet pair density wave.

Press Coverage

Physics World: Topological superconductor harbours unusual crystalline state

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phys.org: New superconducting state could be significant for quantum computing future

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Echo Live: UCC research breakthrough could have consequences for the future of computing

AZo Quantum: New topological quantum matter state promises breakthrough

Cornell Chronicle: Breakthrough identifies new state of topological quantum matter

Yahoo Finance: Quantum computers could be even more powerful with latest discovery

Semiconductor Engineering: UTe₂ breakthrough for quantum computing