The tetragonal heavy-fermion superconductor CeRh2As2 (Tc=0.3 K) exhibits an exceptionally high critical field of 14 T for B∥c. It undergoes a field-driven first-order phase transition between superconducting (SC) states, potentially transitioning from spin-singlet to spin-triplet superconductivity. To elucidate the underlying pairing mechanism, we probe spin fluctuations in CeRh2As2 using neutron scattering. We find dynamic (π,π) antiferromagnetic spin correlations with an anisotropic quasi-two-dimensional correlation volume. Our data place an upper limit of 0.31 μB on the staggered magnetization of corresponding N\'{e}el orders at T=0.08 K. Density functional theory (DFT) calculations, treating Ce 4f electrons as core states, show that the AFM wave vector connects significant areas of the Fermi surface. Our findings show the dominant excitations in CeRh2As2 for ℏω<1.2~meV are magnetic and indicate superconductivity in CeRh2As2 is mediated by AFM spin fluctuations associated with a proximate quantum critical point.
@article{arxiv.2406.03566,
title = {Quasi-two-dimensional Antiferromagnetic Spin Fluctuations in the Spin-triplet Superconductor Candidate CeRh$_2$As$_2$},
author = {Tong Chen and Hasan Siddiquee and Zack Rehfuss and Shiyuan Gao and Chris Lygouras and Jack Drouin and Vincent Morano and Keenan E. Avers and Christopher J. Schmitt and Andrey Podlesnyak and Sheng Ran and Yu Song and Collin Broholm},
journal= {arXiv preprint arXiv:2406.03566},
year = {2024}
}