The ternary chalcogenide Bi2⁢Rh3⁢Se2 was found to be a charge density wave (CDW) superconductor with a 2×2 periodicity. The key questions regarding the underlying mechanism of CDW state and its interplay with lattice and electronic properties remain to be explored. Here, based on the systematic Raman scattering investigations on single-crystalline Bi2⁢Rh3⁢Se2, we observed the fingerprinting feature of a CDW state, a collective amplitude mode at ∼39cm−1. The temperature evolution of Raman shift and linewidth for this amplitude mode can be well described by the critical behavior of two-dimensional (2D) Ising model, suggesting the interlayer interactions of Bi2⁢Rh3⁢Se2 are negligible when the CDW state is formed, as a consequence, the quantum fluctuations play an important role at low temperature. Moreover, the temperature dependence of Raman shift for the 𝐴9𝑔 mode deviates significantly from the expected anharmonic behavior when approaching the CDW transition temperature ∼240K, demonstrated that strong electron-phonon coupling plays a key role in the formation of CDW. Our results reveal that Bi2⁢Rh3⁢Se2 is an intriguing quasi-2D system to explore the quantum Ising model and modulate the correlations between CDW and superconductivity.

中文翻译：

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Bi2Rh3Se2 的拉曼光谱研究：二维 Ising 电荷密度波和量子涨落


发现三元硫系元素 Bi2Rh3Se2 是具有 2×2 周期性的电荷密度波 （CDW） 超导体。关于 CDW 状态的潜在机制及其与晶格和电子特性的相互作用的关键问题仍有待探索。在这里，基于对单晶 Bi2Rh3Se2 的系统拉曼散射研究，我们观察到了 CDW 状态的指纹识别特征，即 ∼39cm-1 处的集体振幅模式。这种振幅模式的拉曼位移和线宽的温度演变可以用二维 （2D） Ising 模型的临界行为很好地描述，这表明当 CDW 状态形成时，Bi2Rh3Se2 的层间相互作用可以忽略不计，因此，量子涨落在低温下起着重要作用。此外，当接近 CDW 转变温度 ∼240K 时，A9g 模式的拉曼位移温度依赖性与预期的非谐波行为显着偏离，这表明强电子-声子耦合在 CDW 的形成中起关键作用。我们的结果表明，Bi2Rh3Se2 是一个有趣的准二维系统，用于探索量子 Ising 模型并调节 CDW 与超导之间的相关性。