Thermodynamics and heat transport in the quantum spin liquid candidates NaYbS 2 and NaYbSe 2

作者：N. Li, Ming Xie, Q. Huang, Zhiwen Zhuo, Zheng Zhang, Eun Sang Choi, Yiyan Wang, Hui Liang, Yongqi Sun, Dandan Wu, Q. J. Li, Haidong Zhou, Gang Chen, Xinguo Zhao, Q. M. Zhang, X. F. Sun · 发表于：Physical review. B./Physical review. B · 年份：2024 · DOI：10.1103/physrevb.110.224414 · 被引用次数：8 · 研究领域：Advanced Condensed Matter Physics、Magnetic and transport properties of perovskites and related materials、Topological Materials and Phenomena

We study the ultralow-temperature thermodynamics and thermal conductivity ($\ensuremath{\kappa}$) of the single-crystal rare-earth chalcogenides ${\mathrm{NaYbS}}_{2}$ and ${\mathrm{NaYbSe}}_{2}$, which have an ideal triangular lattice of the ${\mathrm{Yb}}^{3+}$ ions and have been proposed to be quantum spin liquid candidates. The magnetic specific heat divided by temperature ${C}_{\mathrm{mag}}/T$ is nearly constant at $T<200$ mK, which is indeed the indication of the gapless magnetic excitations with a constant density of states. However, we observe a vanishingly small residual term ${\ensuremath{\kappa}}_{0}/T$, which points to the absence of mobile fermionic excitations in these materials. Both the weak temperature dependence of $\ensuremath{\kappa}$ and the strong magnetic-field dependence of $\ensuremath{\kappa}$ suggest the significant scattering between the spinons and phonons, which actually supports the existence of a gapless or tiny-gapped quantum spin liquid. Moreover, the $\ensuremath{\kappa}(B)/\ensuremath{\kappa}(0)$ isotherms show a series of field-induced magnetic transitions for $B\ensuremath{\parallel}a$, confirming the easy-plane anisotropy, which is consistent with the results of ac magnetic susceptibility. We expect our results to inspire further interests in the understanding of the spinon-phonon coupling in the spin liquid systems.