2026/06/17 by Nan Jiang, Yijin Zhang, Yujie Xia +10
Materials Science · Physics and Astronomy · #Chemical and Physical Properties of Materials #Magnet #Molecular magnets #Quantum and electron transport phenomena #Raman spectroscopy #Spectroscopy #Topological Materials and Phenomena #van der Waals force
paper · pdf · doi:10.1103/n87n-h8p5
published in Physical review. B./Physical review. B 114(6) (American Physical Society)
openalex publication_date 2026/06/17 · openalex created_date 2026/06/18 · openalex updated_date 2026/08/05
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 A1g modes under an out-of-plane magnetic field. Based on symmetry considerations, we attribute this dichroic response to chiral A1g 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.