Molecular interactions induced collapse of charge density wave quantum states in 2H tantalum disulfide nanosheets

2H-tantalum disulfide (2H-TaS₂) is a layered metallic transition metal dichalcogenide (TMD) that has recently been studied from the perspective of new physics phenomena, including simultaneous lattice distortion and charge density modulation known as the charge density wave (CDW) phase. Here we explored the collapse of CDW states in few-layer 2H-TaS₂ induced by molecular interactions using Raman spectroscopy. Our results indicate that the CDW states disappear in few-layer 2H-TaS₂ with rhodamine 6G (R6G) adsorbed due to the charge transfer, which is reflected by the change of behaviors of lattice vibrational modes in 2H-TaS₂. We observed the 2-phonon mode that signifies the CDW formation in 2H-TaS₂, and becomes a phonon-hardened mode when R6G molecules are absorbed on its surface. R6G adsorption further induces the breakdown of the Raman polarization selection rule in 2H-TaS₂, which results in the alteration of the A_1g phonon mode polarization state of 2H-TaS₂. This study can shed light not only on the underlying mechanisms of CDW states but also on controlling the CDW states under a variety of environmental conditions.