Department of Physics and Astronomy, Rice Center for Quantum Materials, Rice University, Houston, TX, USA.
National High Magnetic Field Laboratory, Florida State University, Tallahassee, FL, USA.
Nature. 2021 Dec;600(7890):636-640. doi: 10.1038/s41586-021-04151-5. Epub 2021 Dec 22.
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 (ref. ). Electron Cooper pairs in most superconductors form anti-parallel spin singlets with total spin S = 0 (ref. ), although they can also form parallel spin-triplet Cooper pairs with S = 1 and an odd parity wavefunction. Spin-triplet pairing is important because it can host topological states and Majorana fermions relevant for quantum computation. Because spin-triplet pairing is usually mediated by ferromagnetic (FM) spin fluctuations, uranium-based materials near an FM instability are considered to be ideal candidates for realizing spin-triplet superconductivity. Indeed, UTe, which has a T ≈ 1.6 K (refs. ), has been identified as a candidate for a chiral spin-triplet topological superconductor near an FM instability, although it also has antiferromagnetic (AF) spin fluctuations. Here we use inelastic neutron scattering (INS) to show that superconductivity in UTe is coupled to a sharp magnetic excitation, termed resonance, at the Brillouin zone boundary near AF order. Because the resonance has only been found in spin-singlet unconventional superconductors near an AF instability, its observation in UTe suggests that AF spin fluctuations may also induce spin-triplet pairing or that electron pairing in UTe has a spin-singlet component.
超导性源于电子束缚（库珀）对的形成，这些电子对在超导转变温度 T 以下可以无阻力地穿过晶格（参考文献）。大多数超导体中的电子库珀对形成反平行自旋单态，总自旋 S=0（参考文献），尽管它们也可以形成平行自旋三重态库珀对，自旋 S=1 且波函数为奇数。自旋三重态配对很重要，因为它可以承载拓扑状态和马约拉纳费米子，这对量子计算很重要。由于自旋三重态配对通常是通过铁磁（FM）自旋涨落介导的，因此处于 FM 不稳定性附近的铀基材料被认为是实现自旋三重态超导的理想候选材料。事实上，具有 T≈1.6 K（参考文献）的 UTe 已被确定为 FM 不稳定性附近手性自旋三重拓扑超导体的候选材料，尽管它也具有反铁磁（AF）自旋涨落。在这里，我们使用非弹性中子散射（INS）表明，UTe 中的超导性与在 AF 序附近的布里渊区边界处的尖锐磁激发，称为共振，耦合在一起。由于共振仅在 AF 不稳定性附近的自旋单重非常规超导体中发现，因此在 UTe 中观察到共振表明 AF 自旋涨落也可能诱导自旋三重态配对，或者 UTe 中的电子配对具有自旋单重态分量。
