Probing Charge Density Waves in K_0.28MoO₃ with Raman Spectroscopy

Quasi-low-dimensional materials have been at the forefront of much modern research, perhaps most prevalently in 2D van der Waals materials, owing to their easily tunable thickness and their electro-optical properties desirable in next-gen technology. One common property among many low-dimensional materials is an electro-phonon instability leading to a spontaneous restructuring of the crystal lattice with accompanying changes in the electro-optical properties, a phenomenon known as a charge density wave (CDW). Such transitions are known to occur in the molybdenum oxides A_xMo_yO_z (A = alkali metal). We study one such material, potassium blue bronze K_0.28MoO₃, by means of temperature-resolved Raman spectroscopy. With a quasi-2D layered crystal structure of readily tunable thickness, quasi-1D transport, and a CDW marked by a metal-semiconductor transition at temperatures near 180 K, potassium blue bronze offers a promising platform to investigate charge-ordering processes via Raman spectroscopy, and any effects thereon due to interlayer-coupling and crystallite thickness.