自旋-1/2三聚体链Na$_2$Cu$_3$Ge$_4$O$_{12}$中的声子反常与临界标度
Phonon anomalies and critical scaling in the spin-$1/2$ trimer chain Na$_2$Cu$_3$Ge$_4$O$_{12}$
浏览论文内容
中文总结 AI 辅助
本研究针对低维量子磁体NCGO开展温度依赖拉曼光谱研究，发现其顺磁-关联量子磁态交叉中存在声子反常与临界标度行为，证实声子重整化由自旋动态驱动，确立其为研究自旋-晶格耦合的模型体系。
中文摘要 AI 辅助
低维量子磁体为探索自旋-晶格耦合介导的量子关联提供了理想平台，这种关联会产生涌现的准粒子激发。Na$_2$Cu$_3$Ge$_4$O$_{12}$（NCGO）中由铜离子构成的反铁磁耦合自旋-1/2三聚体链存在不同种类的高能自旋激发，其能量尺度与晶格振动的能量尺度重叠。本文报道了在80 K至400 K范围内开展的系统温度依赖拉曼光谱研究。通过分析宽光谱背景得到的动态自旋磁化率显示，准粒子激发在170 K以下出现。我们进一步发现，当材料从正常顺磁态转变为关联量子磁态时，声子动力学出现了反常的交叉行为。观测到声子模的积分拉曼磁化率满足幂律依赖关系$I_{χ^{\u2033}}^{i}\sim|T-T_{c}|^β$，其中临界温度$T_c$=167$\pm$1 K，临界指数$β= 0.24\pm 0.02$。结合宽光谱背景和尖锐声子峰的结果进一步表明，交叉过程中观测到的声子重整化由动态自旋态驱动。此外，通过对80 K下记录的200条光谱进行矩阵范数和幂检验分析，量化得到的声子能量本征值之间的统计关联揭示了声子模之间出乎意料的线性相关性，这也表明集体晶格响应受自旋关联调控。这些研究结果确立了NCGO作为研究低维磁性材料中协同自旋-晶格耦合和声子动力学临界标度行为的模型体系。
英文摘要
Low-dimensional quantum magnets provide an ideal platform to explore spin-lattice coupling-mediated quantum correlations, which give rise to emergent quasiparticle excitations. The antiferromagnetically coupled spin-1/2 trimer chain of copper ions in Na$_2$Cu$_3$Ge$_4$O$_{12}$ (NCGO) hosts high-energy spin excitations of different species, whose energy scales overlap with those of lattice vibrations. Here, we report a comprehensive temperature-dependent Raman spectroscopic study performed between 80 and 400 K. The dynamic spin susceptibility, as obtained from the analysis of the broad spectral background, reveals the emergence of quasiparticle excitations below 170 K. We further identify an unusual crossover of phonon dynamics when the material transits from a normal paramagnetic state to a correlated quantum magnetic state. A power law dependence of the integrated Raman susceptibility of the phonon modes, $I_{χ^{\prime\prime}}^{i}\sim|T-T_{c}|^β$, is observed with the critical temperature $T_c$=167$\pm$1 K, and critical exponent $β= 0.24\pm 0.02$. The combined results obtained from the broad spectral background and sharp phonon peaks further indicate that the phonon renormalization observed across the crossover is driven by dynamic spin states. Additionally, statistical correlations among phonon energy eigenvalues, quantified through matrix-norm and power-test analyses of 200 spectra recorded at 80 K, reveal an unexpected linear correlation among phonon modes, also indicating that the collective lattice response is governed by spin correlations. These findings establish NCGO as a model system for investigating cooperative spin-lattice coupling and critical scaling behavior of phonon dynamics in low-dimensional magnetic materials.
