Spin-triplet topological superconductors should exhibit many unprecedented electronic properties including fractionalized electronic states relevant to quantum information processing. Although UTe2 may embody such bulk topological superconductivity, its superconductive order-parameter ∆k remains unknown. Many diverse forms for ∆k are physically possible in such heavy fermion materials. Moreover, intertwined density waves of spin (SDW), charge (CDW) and pairs (PDW) may interpose, with the latter exhibiting spatially modulating superconductive order-parameter ∆r , electron pair density and pairing energy-gap. Hence, the newly discovered CDW state in UTe2 motivates the prospect that a PDW state may exist in this material. To search for it, we visualize the pairing energy-gap with μeV-scale energy-resolution using superconductive STM tips. We detect three PDWs, each with peak-peak gap modulations circa 10 μeV and at incommensurate wavevectors Pi=1,2,3 that are indistinguishable from the wavevectors Qi=1,2,3 of the prevenient CDW. Concurrent visualization of the UTe2 superconductive PDWs and the non-superconductive CDWs reveals that every Pi:Qi pair exhibits a relative spatial phase δϕ≈π. From these observations and given UTe2 as a spin-triplet superconductor, this PDW state should be a spin-triplet pair density wave. While such states do exist in superfluid 3He, for superconductors they are unprecedented.
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Interplay of PDW and CDW in UTe2