Abstract
The tetragonal heavy-fermion superconductor CeRh2β’As2 (πc =0.3ββK) exhibits an exceptionally high critical field of 14 T for π β₯π. It undergoes a field-driven first-order phase transition between superconducting states, potentially transitioning from spin-singlet to spin-triplet superconductivity. To further understand these superconducting states and the role of magnetism, we probe spin fluctuations in CeRh2β’As2 using neutron scattering. We find dynamic (π,π) antiferromagnetic (AFM) spin correlations with an anisotropic quasi-two-dimensional correlation volume. Our data place an upper limit of 0.31ββπB on the staggered magnetization of corresponding NΓ©el orders at π =0.08ββK. Density functional theory calculations, treating Ce 4β’π electrons as core states, show that the AFM wave vector connects significant areas of the Fermi surface. Our findings indicate that the dominant excitations in CeRh2β’As2 for ββ’π <1.2ββmeV are magnetic and suggest that superconductivity in CeRh2β’As2 is mediated by AFM spin fluctuations associated with a proximate quantum critical point.
