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arXiv · 2406.03566

Quasi-two-dimensional Antiferromagnetic Spin Fluctuations in the Spin-triplet Superconductor Candidate CeRh$_2$As$_2$

Tong Chen·Hasan Siddiquee·Zack Rehfuss·Shiyuan Gao·Chris Lygouras·Jack Drouin·Vincent Morano·Keenan E. Avers·Christopher J. Schmitt·Andrey Podlesnyak·Sheng Ran·Yu Song·Collin Broholm
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Abstract

The tetragonal heavy-fermion superconductor CeRh$_2$As$_2$ ($T_{\rm c}=0.3$ K) exhibits an exceptionally high critical field of 14 T for $\textbf{B} \parallel \textbf{c}$. 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 CeRh$_2$As$_2$ using neutron scattering. We find dynamic $(\pi,\pi)$ antiferromagnetic spin correlations with an anisotropic quasi-two-dimensional correlation volume. Our data place an upper limit of 0.31 $\mu_{\rm B}$ 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 CeRh$_2$As$_2$ for $\hbar\omega< 1.2$~meV are magnetic and indicate superconductivity in CeRh$_2$As$_2$ is mediated by AFM spin fluctuations associated with a proximate quantum critical point.

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Tong Chen, Hasan Siddiquee, Zack Rehfuss, Shiyuan Gao, Chris Lygouras, Jack Drouin, Vincent Morano, Keenan E. Avers, Christopher J. Schmitt, Andrey Podlesnyak, Sheng Ran, Yu Song, Collin Broholm. 2024-06-05. Quasi-two-dimensional Antiferromagnetic Spin Fluctuations in the Spin-triplet Superconductor Candidate CeRh$_2$As$_2$. https://arxiv.org/abs/2406.03566

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