The nature of low-temperature spin-freezing in frustrated Kitaev magnets

The subtle interplay between competing degrees of freedom, anisotropy, and spin correlations in frustrated Kitaev magnets offers an ideal platform to host non-trivial spin freezing and exotic low-energy excitations. We elucidate low-temperature spin freezing as evidenced by thermodynamics, NMR, and inelastic neutron scattering (INS) results in frustrated Kitaev magnets adopting Halperin and Saslow (HS) and spin jam frameworks. The temperature dependence of specific heat (Cm) shows a broad maximum, indicating short-range spin correlations, while the T2 dependence of Cm below the spin-glass temperature (Tg) suggests gapless excitation spectra. The aging and memory effect experiments suggest a non-hierarchical free energy distribution, which differs from the hierarchical organization of conventional spin freezing. The NMR spin-lattice relaxation rate follows a power law behavior below Tg, suggesting exotic spin excitation spectra that are supported by the INS. The INS susceptibility is proportional to the energy transfer, corroborating the emergence of topological spin freezing, which can be explained by the HS hydrodynamic modes. HS modes account for instigating non-Abelian defect propagation, thereby inducing a spin jam state in the low-T regime in Kitaev magnets. Our work captures the essence of topological spin freezing, characterized by macroscopic ground state degeneracy, short-range spin correlations, and linearly dispersive low-energy excitations in frustrated Kitaev magnets. The interplay between competing degrees of freedom, anisotropy, and spin correlations in frustrated Kitaev magnets is an ideal platform to observe non-trivial spin freezing. Here, thermodynamics, nuclear magnetic resonance and inelastic neutron scattering reveal the presence of exotic spin jam states in these quantum materials.