Unveiling quantum phases in two-dimensional materials with optical quasiparticle probes

Two-dimensional (2D) materials offer unprecedented platforms for exploring emergent quantum phenomena, driven by a rich variety of optically active quasiparticles. However, a unified framework capturing how reduced dimensionality and interactions reshape their spectral properties remains elusive, with many studies addressing individual effects in isolation. This review outlines recent advances in optical spectroscopies to reveal the interplay between phonons, magnons, excitons, and polaritons in 2D systems. We show how Raman spectroscopy experiments uncover charge density wave transitions and their tunability via dimensional confinement. Moiré excitons emerge as powerful optical probes, providing insights into carrier localization, Mott and Wigner crystallization, and excitonic insulator phases in strongly correlated moiré heterostructures. Magneto-Raman and other magneto-optical techniques expose the magnon quasiparticle, spin-lattice coupling, and emergent magnetic orders, enabling studies of nonlinear spin dynamics and candidate quantum spin liquids. Altogether, optical probes offer non-destructive access to electronic and magnetic orders in 2D systems, opening new opportunities for engineering quantum phases and developing photonic, spintronic, and quantum technologies.