Detection of a pair density wave state in UTe2

• Published in: Nature (London) Vol. 618; no. 7967; pp. 921 - 927
• Main Authors: Gu, Qiangqiang, Carroll, Joseph P., Wang, Shuqiu, Ran, Sheng, Broyles, Christopher, Siddiquee, Hasan, Butch, Nicholas P., Saha, Shanta R., Paglione, Johnpierre, Davis, J. C. Séamus, Liu, Xiaolong
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 29.06.2023; Nature Publishing Group
• Subjects: 639/766/119/1003; 639/766/119/2792; 639/766/119/995; Data processing; Density; Electron states; Electronic properties; Electrons; Energy; Energy gap; Energy resolution; Fermions; Fourier transforms; Humanities and Social Sciences; Information processing; Magnetic fields; Microscopy; multidisciplinary; Order parameters; Quantum phenomena; Scanning tunneling microscopy; Science; Science & Technology - Other Topics; Science (multidisciplinary); Superconductors; Symmetry; Topography; Topological superconductors; Visualization
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/s41586-023-05919-7

Spin-triplet topological superconductors should exhibit many unprecedented electronic properties, including fractionalized electronic states relevant to quantum information processing. Although UTe 2 may embody such bulk topological superconductivity 1 – 11 , its superconductive order parameter Δ( k ) remains unknown 12 . Many diverse forms for Δ( k ) are physically possible 12 in such heavy fermion materials 13 . Moreover, intertwined 14 , 15 density waves of spin (SDW), charge (CDW) and pair (PDW) may interpose, with the latter exhibiting spatially modulating 14 , 15 superconductive order parameter Δ( r ), electron-pair density 16 – 19 and pairing energy gap 17 , 20 – 23 . Hence, the newly discovered CDW state 24 in UTe 2 motivates the prospect that a PDW state may exist in this material 24 , 25 . To search for it, we visualize the pairing energy gap with μeV-scale energy resolution using superconductive scanning tunnelling microscopy (STM) tips 26 – 31 . We detect three PDWs, each with peak-to-peak gap modulations of around 10 μeV and at incommensurate wavevectors P i =1,2,3 that are indistinguishable from the wavevectors Q i =1,2,3 of the prevenient 24 CDW. Concurrent visualization of the UTe 2 superconductive PDWs and the non-superconductive CDWs shows that every P i : Q i pair exhibits a relative spatial phase δϕ  ≈ π. From these observations, and given UTe 2 as a spin-triplet superconductor 12 , this PDW state should be a spin-triplet PDW 24 , 25 . Although such states do exist 32 in superfluid 3 He, for superconductors, they are unprecedented. A spin-triplet pair density wave is discovered in the candidate topological superconductor UTe 2 using superconductive scanning tunnelling microscopy tips.