Inelastic neutron scattering measurements of field dependence of magnetic excitations in UTe₂

Heavy-fermion materials are a rich platform for correlated electron physics, with one important example being unconventional superconductivity. UTe₂ has attracted great attention due to its potential for realizing spin-triplet (ST) superconductivity. In UTe₂, it is widely believed that the pairing mechanism for superconducting Cooper pairs is mediated by magnetism rather than phonons. However, little is known regarding the magnetic interactions between the itinerant spins, with conflicting reports regarding if they are dominantly ferromagnetic, antiferromagnetic, or some combination of the two [1-4]. Superconductivity in UTe₂ is resilient to large applied magnetic fields, and at even higher fields shows exotic behavior like reentrant superconductivity at 35 T [1,2]. Our recent inelastic scattering work [5] found that for fields along the crystalline c-axis, the excitations are completely field-independent. This, along with support from DFT+DMFT calculations, led to the conclusion that the magnetic excitations in UTe₂ originate not from spin-spin interactions as in an ordered magnet, but instead from electronic interband excitations between hybridized itinerant f-bands, where the electrons are excited between regions with high density of states. In this talk, we follow up on this work with additional inelastic neutron scattering measurements, further characterizing the excitations of this exotic material in the influence of applied magnetic fields.

[1] S. Ran et al., Science 365, 684 (2019)

[2] Sylvia K Lewin et.al., 2023 Rep.Prog.Phys. 86 114501

[3] C. Duan, et al., Phys. Rev. Lett. 125, 237003 (2020).

[4] Duan, C., Baumbach, R.E., Podlesnyak, A. et al. Nature 600, 636–640 (2021).

[5] T. Halloran et al., arxiv:2408.14619 (2024)