Resonance from antiferromagnetic spin fluctuations for superconductivity in UTe 2 .

Publisher: Nature Publishing Group Country of Publication: England NLM ID: 0410462 Publication Model: Print-Electronic Cited Medium: Internet ISSN: 1476-4687 (Electronic) Linking ISSN: 00280836 NLM ISO Abbreviation: Nature Subsets: PubMed not MEDLINE; MEDLINE

Publication: Basingstoke : Nature Publishing Group
Original Publication: London, Macmillan Journals ltd.

Superconductivity originates from the formation of bound (Cooper) pairs of electrons that can move through the lattice without resistance below the superconducting transition temperature T c (ref.  ¹ ). Electron Cooper pairs in most superconductors form anti-parallel spin singlets with total spin S = 0 (ref.  ² ), although they can also form parallel spin-triplet Cooper pairs with S = 1 and an odd parity wavefunction ³ . Spin-triplet pairing is important because it can host topological states and Majorana fermions relevant for quantum computation ^4,5 . Because spin-triplet pairing is usually mediated by ferromagnetic (FM) spin fluctuations ³ , uranium-based materials near an FM instability are considered to be ideal candidates for realizing spin-triplet superconductivity ⁶ . Indeed, UTe 2 , which has a T c  ≈ 1.6 K (refs.  ^7,8 ), has been identified as a candidate for a chiral spin-triplet topological superconductor near an FM instability ^7-14 , although it also has antiferromagnetic (AF) spin fluctuations ^15,16 . Here we use inelastic neutron scattering (INS) to show that superconductivity in UTe 2 is coupled to a sharp magnetic excitation, termed resonance ^17-23 , at the Brillouin zone boundary near AF order. Because the resonance has only been found in spin-singlet unconventional superconductors near an AF instability ^17-23 , its observation in UTe 2 suggests that AF spin fluctuations may also induce spin-triplet pairing ²⁴ or that electron pairing in UTe 2 has a spin-singlet component.
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