Conspectusvan der Waals (vdW) materials, covering both individual monolayers and multilayer stacks with strong in-plane bonding and weak interlayer interactions, if any, offer a versatile platform for investigating novel quantum phenomena and designing atomic-scale heterostructures. The growing diversity of this material family, ranging from isotropic graphene to anisotropic black phosphorus and emerging magnetic layers, requires advanced characterization tools to probe their lattice structure and lattice vibration information. In this scenario, Raman spectroscopy has established itself as a key nondestructive method for analyzing lattice vibrations and material properties. Recently, angle-resolved polarized Raman (ARPR) spectroscopy has evolved from a tool for basic symmetry identification into a powerful quantitative technique for elucidating multidimensional light–matter interactions within vdW systems and their artificial stacks by disentangling intrinsic phonon properties from extrinsic optical effects. In condensed matter physics, this technique provides a vital, noninvasive bridge between microscopic lattice behavior and macroscopic optical response, enabling the rational design of materials with tailored vibrational, electronic, and optical functionalities. Its ability to operate under diverse conditions, including in situ, under strain, or in applied external fields, makes ARPR spectroscopy an indispensable tool in the advancing toolkit for vdW material research.In this Account, we detail the transition of the significant advances in ARPR spectroscopy from a qualitative symmetry probe to a quantitative platform for investigating vdW systems. We begin with a conceptual introduction to polarized Raman scattering, explaining how to describe and further probe phonon symmetry with the involvement of the Raman tensor and the Raman selection rule. A central theme is the distinctive concepts of the intrinsic Raman tensor Rint, which captures the inherent electron–phonon/photon interactions of materials, and the effective Raman tensor Reff, which additionally incorporates the complicated dependence on the optical properties of the sample and underlying substrates. Technically, we highlight key experimental advances, such as in situ polarization control for high-quality ARPR acquisition and Zenith-ARPR configurations that extend phonon characterization to the out-of-plane dimension. We next demonstrate some fundamental symmetry analysis based on Raman spectroscopy in isotropic crystals, finally clarify the anomalous ARPR response in anisotropic materials, and further demonstrate how our recently developed quantitative framework resolves the puzzling thickness-, wavelength-, and substrate-dependent ARPR anomalies that have long hindered interpretation. Taking black phosphorus as a representative, we show that an intrinsic Rint can predict ARPR responses across diverse sample structures even under resonant conditions. The extracted tensor elements, including their complex phase differences, are closely linked to the microscopic anisotropic electron–phonon/photon coupling and quantum interference among scattering pathways in the Brillouin zone. Collectively, this work underscores ARPR spectroscopy as a cornerstone technique for quantitatively understanding polarization-dependent light–matter interactions in vdW materials.
Xie et al. (Wed,) studied this question.