Giant tunability of superlattice excitations in chiral Cr1/3TaS2

Layered chalcogenides are superb platforms for exploring tunable functionality and the impact of external stimuli, and when intercalated with metal atoms, there are opportunities to reveal unique guest–host interactions. One barrier to greater control of the collective metal monolayer excitations in these materials is the absence of detailed information about how they evolve under compression. In order to explore superlattice excitations in a series of intercalated chalcogenides, we measured the Raman scattering response of Cr_1/3TaS₂ under pressure and compared our findings with the behavior of Cr_1/3NbS₂, Fe_1/3TaS₂, and Fe_1/4TaS₂. Overall, we find that the metal monolayer excitations are sharp and strong, spanning a significant portion of the teraHertz range. Analysis reveals that chalcogen layer thickness and size of the van der Waals gap to that of the A site ion are sufficient to divide these materials into two classes: the Cr analogs with relatively little distortion of the metal monolayer excitations under compression and the Fe analogs that host substantial symmetry breaking. In addition to unraveling these structure-property relations, we combine pressure and strain to demonstrate that the superlattice excitation in Cr_1/3TaS₂ can be tuned in a nearly linear fashion by approximately 16% overall in frequency space—a significant advance for spintronics and photonics applications.