Investigation of the Paramagnetic State of the Kagome Kondo Lattice Compound YbV${}_6$Sn${}_6$: a ${}^{51}$V Nuclear Magnetic Resonance Study

Abstract

YbV${}_6$Sn${}_6$ is a recently discovered kagome-lattice metal that orders at $T_{\mathrm{N}}\approx 0.4$~K. Its layered structure combines a triangular Kondo lattice of Yb${}^{3+}$ ions with vanadium-based kagome planes, which may host an interplay between strong correlations and band topology. We report a ${}^{51}$V nuclear magnetic resonance (NMR) study of the paramagnetic state of YbV${}_6$Sn${}_6$. Detailed field-angular dependence of single-crystal NMR spectra determined the principal-axis directions of the electric field gradient tensor at the ${}^{51}$V sites, as well as their nuclear quadrupole frequency, ${\nu }_{\mathrm{Q}}$, and asymmetry parameter, $\eta$. The Knight shift, $K$, was measured for different field orientations, and the analysis of $K$ against magnetic susceptibility to extract anisotropic hyperfine couplings. Accurate spectral assignments further enabled measurements of the nuclear spin-lattice relaxation rate, $1/T_1$, for both in-plane and out-of-plane field directions. The temperature dependence of $1/T_1$ shows that out-of-plane spin fluctuations are suppressed below $\sim$20~K, whereas in-plane fluctuations are markedly enhanced, which might be understood by thermal depopulation of the low-lying crystalline electric field excited state. The notable anisotropy in $1/T_1$ indicates that the paramagnetic state of YbV${}_6$Sn${}_6$ is strongly affected by in-plane spin dynamics.