Darkness in interlayer and charge density wave states of 2H-TaS2

The wavelike nature of electrons is evident from quantum interference effects observed during the photoemission process. When there are different nuclei in the unit cell of a crystal and/or structural distortions, photoelectron wave functions can interfere, giving rise to a peculiar intensity modulation of the spectrum, which can also hide energy states in a photoemission experiment. The 2H phase of transition metal dichalcogenides, with two nonequivalent layers per unit cell and charge density wave distortion, is an optimal platform for such effects to be observed. Here, we discover undetectable states in 2H-TaS2, interpreting high-resolution angular resolved photoemission spectroscopy considering interference effects of the correlated electron wave functions. In addition, phase mismatching induced by charge density wave distortion results in an evident signature of the phase transition in the photoemission spectrum. Our results highlight the importance of quantum interference, electronic correlations, and structural distortion to understand the physics of layered materials.