低温热力学性质：$S_{\mathrm{eff}}=1/2$ 三角晶格量子自旋液体候选材料 TlYbS$_2$
Low temperature thermodynamics of $S_{\mathrm{eff}}=1/2$ triangular lattice quantum spin liquid candidate TlYbS$_2$
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中文总结 AI 辅助
本文通过单晶 TlYbS$_2$ 的低温磁化、比热等测量，发现零场下约 530 mK 的弱异常及 $C_m\propto T^{1.8}$ 行为，并揭示强易平面各向异性与场致量子自旋液体转变。
中文摘要 AI 辅助
几何阻挫的三角晶格反铁磁体在磁有序和量子自旋液体（QSL）行为之间表现出微妙的竞争，其中基于 Yb 的 delafossite 家族 $A$Yb$X_2$ 为探索这一物理提供了结构清洁的平台。在此，我们报告了使用直流磁化、交流磁化率、电子自旋共振（ESR）和比热测量对单晶 TlYbS$_2$ 进行的全面研究，测量范围从室温延伸到毫开尔文温区。单晶 X 射线衍射确认了三角 $R\bar{3}m$ 结构，该结构由 Yb$^{3+}$ 离子组成的良好分离的三角层构成，且未检测到可观测的位点无序。在零场下，在约 $530$ mK 附近观察到微弱的热力学异常，这可能表明类似于 KYbSe$_2$ 中报道的弱有序态的开始。在 $300$ mK 以下，零场磁比热遵循 $C_{\rm m}\propto T^{1.8}$，接近二次温度依赖关系，这与姊妹化合物 TlYbSe$_2$ 中报道的线性温度依赖关系形成对比，后者被描述为自旋子与热激发规范通量激发之间的相互作用。磁化和 ESR 测量确定了显著的易平面磁各向异性，$g_\perp/g_\parallel \approx 6.9$。约 $530$ mK 处的异常对磁场表现出强烈的各向异性响应。对于 $H\perp c$，该异常在高达约 $2$ T 的磁场下仍然可见，并在约 $2.5$ T 以上连续演变为场致有序相，随后是一系列场致相，包括在约 $5$ 至 $8$ T 之间的 $1/3$ 磁化平台和约 $17$ T 附近的完全极化。相比之下，对于 $H\parallel c$，该异常减弱并在约 $3$ T 附近被抑制，这与最近报道的从有序态到场致 QSL 的禁闭-去禁闭转变一致。
英文摘要
Geometrically frustrated triangular-lattice antiferromagnets exhibit a delicate competition between magnetic order and quantum spin liquid (QSL) behavior, with the Yb-based delafossite family $A$Yb$X_2$ providing a structurally clean platform for exploring this physics. Here, we report a comprehensive study of single-crystal TlYbS$_2$ using DC magnetization, AC susceptibility, electron spin resonance (ESR), and specific heat measurements extending from room temperature to the millikelvin regime. Single-crystal X-ray diffraction confirms a trigonal $R\bar{3}m$ structure comprising well-separated triangular layers of Yb$^{3+}$ ions with no detectable site disorder. At zero field, a weak thermodynamic anomaly is observed near $530$ mK, which may indicate the onset of a weakly ordered state similar to that reported in KYbSe$_2$. Below $300$ mK, the zero-field magnetic specific heat follows $C_{\rm m}\propto T^{1.8}$, close to a quadratic temperature dependence, in contrast to the linear temperature dependence reported for the sister compound TlYbSe$_2$, which has been described in terms of the interplay between spinons and thermally excited gauge-flux excitations. Magnetization and ESR measurements establish pronounced easy-plane magnetic anisotropy, with $g_\perp/g_\parallel \approx 6.9$. The anomaly near $530$ mK exhibits a strongly anisotropic response to magnetic field. For $H\perp c$, it remains visible up to approximately $2$ T and continuously evolves toward a field-induced ordered phase above approximately $2.5$ T, followed by a sequence of field-induced phases that includes a $1/3$ magnetization plateau between approximately $5$ and $8$ T and full polarization near $17$ T. In contrast, for $H\parallel c$, the anomaly weakens and is suppressed near $3$ T, consistent with the recently reported confinement--deconfinement transition from an ordered state to a field-induced QSL.
发表机构
- Purdue University（普渡大学）
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