${}^{133}$Cs and ${}^{75}$As NMR investigation of the normal metallic state of the quasi-one-dimensional Cs${}_2$Cr${}_3$As${}_3$

Abstract

We report ${}^{133}$Cs NMR and ${}^{75}$As Nuclear Quadrupole Resonance (NQR) measurements on the normal metallic state above $T_c$ of a quasi-one-dimensional superconductor Cs${}_2$Cr${}_3$As${}_3$ ($T_c<1.6$~K). From the ${}^{133}$Cs NMR Knight shift ${}^{133}K$ measured at the Cs1 site, we show that the uniform spin susceptibility ${\chi }_{spin}$ increases from 295~K to $\sim$ 60~K, followed by a mild suppression; ${\chi }_{spin}$ then levels off below $\sim$10~K. In contrast, a vanishingly small magnitude of ${}^{133}K$ indicates that Cs2 sites contribute very little to electrical conduction and the exchange interactions between 3d electrons at Cr sites. Low frequency Cr spin dynamics, reflected on ${}^{75}$As $1/T_{1}T$ (the nuclear spin-lattice relaxation rate $1/T_1$ divided by temperature $T$), shows an analogous trend as ${\chi }_{spin}$. Comparison with the results of $1/T_{1}T$ near $T_c$ with Rb${}_2$Cr${}_3$As${}_3$ ($T_c=6.1$~K) and Rb${}_2$Cr${}_3$As${}_3$ ($T_c=4.8$~K) establishes a systematic trend that substitution of K${}^{+}$ ions with larger alkali ions progressively suppresses Cr spin fluctuations together with $T_c$.

Final accepted version with 11 Figures