Quasi-two-dimensional Antiferromagnetic Spin Fluctuations in the Spin-triplet Superconductor Candidate CeRh₂As₂

Spin-triplet superconductors may harbor topological states and Majorana fermions relevant to quantum computation. A major challenge is identifying compounds that may realize this phase and establishing the nature and pairing mechanism of the superconductivity. In the tetragonal heavy-fermion superconductor CeRh₂As₂ ( = 0.26 K), a phase transition between superconducting states for c-axis-oriented magnetic fields has been proposed to be a spin-singlet to spin-triplet transition [1]. In an effort to characterize the superconductivity and the underlying pairing mechanism, we use neutron scattering to probe the antiferromagnetic (AF) spin fluctuations in CeRh₂As₂. In the absence of static magnetic order, we reveal the presence of quasi-two-dimensional commensurate AF spin fluctuations centered at = (1/2 1/2) with a spectrum extending up to at least 1.0 meV. connects large areas of the Fermi surface calculated with Ce electrons in the core using density functional theory. Since the dominant low-energy excitations in CeRh₂As₂ are magnetic, these findings indicate superconductivity in CeRh₂As₂ is mediated by AF spin fluctuations.

[1] Khim, S., et al. "Field-induced transition within the superconducting state of CeRh2As2." Science 373.6558 (2021): 1012-1016.