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arXiv · 1911.02057

Impurity Moments Conceal Low-Energy Relaxation of Quantum Spin Liquids

A. Pustogow·T. Le·H. -H. Wang·Yongkang Luo·E. Gati·H. Schubert·M. Lang·S. E. Brown
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Abstract

We scrutinize the magnetic properties of $\kappa$-(BEDT-TTF)$_2$Hg(SCN)$_2$Cl through its first-order metal-insulator transition at $T_{\rm CO}=30$ K by means of $^1$H nuclear magnetic resonance (NMR). While in the metal we find Fermi-liquid behavior with temperature-independent $(T_1T)^{-1}$, the relaxation rate exhibits a pronounced enhancement when charge order sets in. The NMR spectra remain unchanged through the transition and no magnetic order stabilizes down to 25 mK. Similar to the isostructural spin-liquid candidates $\kappa$-(BEDT-TTF)$_2$Cu$_2$(CN)$_3$ and $\kappa$-(BEDT-TTF)$_2$Ag$_2$(CN)$_3$, $T_1^{-1}$ acquires a dominant maximum (here around 5 K). Field-dependent experiments identify the low-temperature feature as a dynamic inhomogeneity contribution that is typically dominant over the intrinsic relaxation but gets suppressed with magnetic field.

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A. Pustogow, T. Le, H. -H. Wang, Yongkang Luo, E. Gati, H. Schubert, M. Lang, S. E. Brown. 2019-11-05. Impurity Moments Conceal Low-Energy Relaxation of Quantum Spin Liquids. https://doi.org/10.1103/physrevb.101.140401

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