Phonons are the most important fundamental collective excitations in condensed matter systems. Understanding the dynamics and interaction of these excitations and their connection to system properties is therefore key to solving some of the most important puzzles in condensed matter physics. Data on long-wavelength acoustic phonons is, however, lacking for most quantum materials, including the countless two-dimensional layered systems displaying new and unexplained phenomena and properties. This is because the energy range in which these excitations reside is inaccessible to the usual experimental probes. In this presentation, we provide an overview of the technique of Brillouin spectroscopy as a versatile and noncontact probe of this class of phonons and present the results of our recent Brillouin scattering experiments on quantum van der Waals solids. These studies will aid in establishing relationships between the elastic, structural, and electronic properties of these systems. Work partially supported by the Natural Sciences and Engineering Research Council of Canada through a Discovery Grant to Andrews (RGPIN-2024-06345).
McNiven et al. (Wed,) studied this question.
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