AI 中文总结
研究范德华化合物GdGaI，结合对称性分析与密度泛函理论计算识别拉曼活性声子，通过光谱实验及分析揭示其晶格特性、磁场下圆二色性及与自旋 - 声子耦合关系，突出其在相关研究中的前景及圆偏振拉曼的探测作用。
AI 中文摘要
我们报道了作为激子绝缘体候选材料的范德华化合物GdGaI的偏振分辨拉曼光谱。通过对称性分析与密度泛函理论计算相结合，识别出六个拉曼活性声子。光谱显示在4K以下只有预期的非谐硬化，未观察到额外峰、软模和能带折叠迹象，表明晶格畸变低于实验灵敏度。此外，在面外磁场下观察到\(A_{1g}\)模式明显的圆二色性，归因于时间反演破缺态中自旋 - 声子耦合产生的具有相反角动量的手性\(A_{1g}\)声子。圆偏振度的温度演化表明圆偏振拉曼光谱可检测短程反铁磁关联的出现。我们的结果突出了GdGaI作为激子序、磁性和圆偏振声子可相互交织的有前景平台，并证明圆偏振拉曼为激子系统中自旋 - 声子耦合提供了灵敏探针。
英文摘要
We report polarization-resolved Raman spectroscopy of a van der Waals compound GdGaI that is a candidate for excitonic insulators. By combining the symmetry analysis with density functional theory calculations, we identify six Raman-active phonons. The spectra exhibit only the expected anharmonic hardening down to 4 K: no additional peaks, no soft modes, and no signatures of zone folding are observed. This result indicates that any lattice distortion is below our experimental sensitivity, supporting an electronically driven origin for the band reconstruction reported by angle-resolved photoemission spectroscopy rather than an electron-phonon-driven mechanism. Moreover, we observe a pronounced circular dichroism of the $A_{1g}$ modes under an out-of-plane magnetic field. Based on symmetry considerations, we attribute this dichroic response to chiral $A_{1g}$ phonons with opposite angular momenta generated by spin-phonon coupling in the time-reversal-broken state. The temperature evolution of the degree of circular polarization further suggests that circularly polarized Raman spectroscopy detects the emergence of short-range antiferromagnetic correlations. Our results highlight GdGaI as a promising platform in which excitonic order, magnetism, and circularly polarized phonons can be intertwined, and demonstrate that circular-polarization Raman provides a sensitive probe of spin-phonon coupling in excitonic systems.
Comments8 pages, 5 figures
Journal refPhys. Rev. B 114, 065128 (2026)
