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arXiv 2407.10076cond-mat.str-el
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Cu$^{2+}$基$S = 1/2$三角晶格反铁磁体中量子自旋液体态的证据

Evidence of quantum spin liquid state in a Cu$^{2+}$-based $S = 1/2$ triangular lattice antiferromagnet

K. Bhattacharya, S. Mohanty, A. D. Hillier, M. T. F. Telling, R. Nath, M. Majumder

AI总结:

本文通过磁化率、比热和μ子自旋弛豫实验,在Sr₃CuTa₂O₉中观测到无能隙量子自旋液体态,其磁比热幂律指数约为2/3,支持自旋子费米面理论。

摘要:

在三钙钛矿$A_3 B B'_2$O$_9$家族中,由于$B$和$B'$位点呈$1:2$有序而形成的层状三角晶格,为探索量子自旋液体(QSLs)的复杂现象提供了一个引人入胜的领域。我们报告了对属于上述家族的Sr$_3$CuTa$_2$O$_9$基态性质的综合研究,通过磁化率、比热和μ子自旋弛豫($μ$SR)实验,测量温度低至0.1 K。磁化率分析表明,自旋晶格是一个近各向同性的$S = 1/2$三角晶格。我们展示了无能隙QSL的观测结果,其中即使温度比交换能($J_{\rm CW}/k_{\rm B} \simeq -5.04$ K)小两个数量级以上,也没有出现常规的自旋有序或冻结效应。零场下的磁比热在1.2 K以下遵循幂律$C_{\rm m} \sim T^η$,其中$η\approx 2/3$,这与自旋子费米面存在的理论预言一致。在1.2 K以下,$μ$SR弛豫率不随温度变化,表明存在QSL态所预期的持续自旋动力学。进一步深入分析纵向场$μ$SR谱,揭示了自旋无序基态中的强动力学关联。所有这些结果都突出了QSL态中自旋纠缠的特征。

英文摘要:

The layered triangular lattice owing to $1:2$ order of $B$ and $B'$ sites in the triple perovskite $A_3 B B'_2$O$_9$ family provides an enticing domain for exploring the complex phenomena of quantum spin liquids (QSLs). We report a comprehensive investigation of the ground state properties of Sr$_3$CuTa$_2$O$_9$ that belongs to the above family, by employing magnetization, specific heat, and muon spin relaxation ($μ$SR) experiments down to the lowest temperature of 0.1~K. Analysis of the magnetic susceptibility indicates that the spin-lattice is a nearly isotropic $S = 1/2$ triangular lattice. We illustrate the observation of a gapless QSL, in which conventional spin ordering or freezing effects are absent, even at temperatures more than two orders of magnitude smaller than the exchange energy ($J_{\rm CW}/k_{\rm B} \simeq -5.04$~K). Magnetic specific heat in zero-field follows a power law, $C_{\rm m} \sim T^η$, below 1.2~K with $η\approx 2/3$, which is consistent with a theoretical proposal of the presence of spinon Fermi surface. Below 1.2~K, the $μ$SR relaxation rate shows no temperature dependence, suggesting persistent spin dynamics as expected for a QSL state. Delving deeper, we also analyze longitudinal field $μ$SR spectra revealing strong dynamical correlations in the spin-disordered ground state. All of these highlight the characteristics of spin entanglement in the QSL state.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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